Following a group-theoretic approach that we have developed recently, we reformulate the Fourier modal method for crossed gratings with C₃ symmetry, i.e., grating structures that are invariant after rotations about the normal of the mean grating plane through angles n(2π/3). By exploiting the structural symmetry of the grating, a general diffraction problem can be decomposed into a linear combination of three symmetrical basis problems. Hence the total diffracted field can be obtained as a superposition of the solutions of three symmetry modes. It is shown theoretically and numerically that when the incident mounting and the truncation scheme make the truncated reciprocal lattice of the diffracted field also have the C₃ symmetry, the number of unknowns in each symmetrical basis problem is cut by 2/3. Therefore, the maximum effective truncation number of the new algorithm is tripled and the total computation time is reduced by a factor of 9. For the case of normal incidence with arbitrary polarization, the reduction factor can be further increased to 27/2. A numerical example is provided to illustrate the effectiveness of the new formulation.

Perturbations arising from sharp discontinuities of surface relief profiles can have significant effects on the field transmitted through diffractive structures. A method utilizing these perturbations is presented for efficient analysis of the response of surface profiles in the non-paraxial domain. Comparison with rigorous diffraction theory proves the method reliable and the numerical feasibility of the approach is much better than that of rigorous methods.

A phase shift in phase mask is split into two half-magnitude phase-shifts in near field, resulting in FBG spectral asymmetry. The errors are removed using new pre-compensating phase mask for binary-phase Dammann sampled multi-channel FBGs.

Strong reemission of the surface plasmons through a single subwavelength aperture is mainly caused by in-phase coupling of the surface localized electromagnetic waves to irradiative modes by periodic groove structures. By introducing a linear chirping in the groove period, we enhance the coupling effect for focusing the reemitted light in near-field region. The linear chirping in the groove structures which have monotonically decreasing period, leads to focusing the reemitted light with the length, depth, and width of the focus in order of wavelength. We show numerically that the focusing ability is dramatically affected by amount of the linear chirping, and that efficient relaying of a diverging Gaussian beam to a photonic crystal waveguide can be achieved.

Optical trapping and manipulation are based on three types of the force and momentum, in the range of pN, to grab, lift and rotate microparticles due to the light intensity or phase distribution. In the first type, particles are trapped in the highest intensity region of the beam due to optical gradient force for high refractive index particles with respective to its surrounding medium. Secondly, orbital angular momentum (OAM) of a beam can be transferred to a particle due to phase singularity within a beam. Thirdly, spin angular momentum (SAM) can be transferred to the particles due to the circular polarization of the beam. In recent years, microfabricated optical elements have been used to modulate the amplitude and phase of the optical beam to create new generation of optical tweezers with additional manipulation dimensions. In this paper, a review of our recent discoveries of optical trapping and manipulation using micro-beam shaping and micro-optical elements will be presented.

An interferometer based on the spatial coherence detection has been developed for absolute height measurement. The location of a coherence peak resulting from the illumination of an extended quasi-monochromatic spatially incoherent light source with zone-plate-like spatial structure gives the longitudinal depth information. Besides simplifying the control of the light source structure, LCD-SLM eliminates the mechanical movement. Experiments of step height detection and profilometry of an object with a rough surface are presented that demonstrate the validity of the principle.

Interferometric imaging systems measure the complex visibility, which is the Fourier transform of the source brightness distribution, according to the van Cittert-Zernike theorem. Both the amplitude and phase of the visibility are needed to produce images of a complex object structure by Fourier inversion. In this paper, by using the generalized imaging theory of a diffraction-limited incoherent imaging system, the pinhole model and the circular aperture model of the interferometry are presented and derived. The approximate condition, which should be followed by optical aperture synthesis imaging interferometry, is obtained by comparing two models. Based on this condition, the angle of field-of-view (FOV) in the object space is analyzed and determined. At the good approximation, the FOV is about one-sixth of an Airy disk of an elementary aperture diffraction. Also the computer simulation results are presented and match the theoretical results very well. This suggests that the extremely high image resolution can be achieved in the interferometric imaging systems, but it generally has a very small field of view. Such imaging systems are suitable only for the astronomical application.

All-optical modules are devices which process and transport optical signals without transforming to electronic signals. They get more attention as the optical communication network becomes more and more complicated. Among them, OADM (optical add drop module) is one of the most important devices in the optical DWDM (dense wavelength division multiplex) network. It plays the role of a node in network to upload/download signals or to route signals for optical performance monitoring. Applied broadly in projection display systems, DLP (Digital Light Processing) from Texas Instruments turns out to be a versatile device for optical signal processing. The working principle of DLP is based on so called switched-blazed-grating. Part of its micro-mirror array can be formed as a dynamic blazed grating with a period of 14 μm by tilting the micro-mirrors at an angle of ±12 degrees. It is expected to function as either a switch or an attenuator by directing total or part of the incident light between the 2^nd and -2^nd diffraction orders. In this paper, we investigate the optical characteristics of a switched-blazed-grating, its application as a re-configurable OADM, and the performance of such a device. Ray tracing and optical analysis of the OADM are made by using package software ASAP from Breault Research Organization. In conclusion, as a mature and reliable MEMS device, DLP-based switched-blazed-grating provides a very versatile platform for digital optical signal processing and can be used as a dynamic optical-networking device with good performance.

Focus shaping with highly focused cylindrical vector beam is an interesting and important topic in both applied optics and physical optics. In this paper, we describe optimization algorithms to design diffractive optical elements for various beam shaping applications. "Optical bubbles" with desired size and numbers for trapping particles and flat-top focusing with low side-lobe to improved micro printing are proposed. Ultra small focus spot with long depth of focus without energy split to extend the region around the image plane is also presented.

A method of designing new light guide plate (LGP) of backlight system is presented in this paper using binary optical technique. Only one such new micro-optical LGP can integrate the function of multi-layer structures which include LGP, diffusion sheet and two prism sheets in the backlight system. The cell aperture’s structure is designed by using ZEMAX software, and the computer’s simulative result is given. It indicates that the output light uniformity of new LGP can reach 96.06%, axis direction center luminance is enhanced 1.52 times than the traditional approximately.

Coupling high-power laser diode array (LDA) beams into a multi-mode fiber is an important way to expand the LDA applications. Transforming LDA beam is an essential step for fiber-coupled LDA. Diffractive grating arrays are used to transform a bar LDA beam with the output power of 40 watts to realize the symmetry of BPPs in fast and slow axis directions in the paper. First, the specifications of the diffractive grating are calculated according to focusing and coupling bar LDA. Second, the 8-level binary diffractive gratings are fabricated based on the binary optical elements processing platform in our lab. Third, the experiment was carried out and results are gotten. The results show that the focusing spot size is about 200μm in diameter and the numerical aperture NA is 0.22, which agree with the calculated and simulated.

Many optical systems used in the infrared spectrum have, so far, adopted binary optical elements (BOE) to achieve a better performance. Especially, in the middle and long infrared spectrum, binary optical elements are commonly used. Thus, limited by the manufacture technology, the applications of binary optics in the visible spectrum are rare. This tentative research aims at finding the practicability of applying BOEs in the visible spectrum. We attempted to replace the reference lens group in the interferometer with a harmonic diffractive/refractive hybrid lens group, expecting that the wave aberration be well-corrected. In this paper, the main procedure of designing a hybrid optical system is introduced with an example of “F2” lens group. After the analysis on the interference pattern and wave front, the comparison between the tested result and theoretical result can be made. It demonstrates that the hybrid optical system is capable of being applied in the visible spectrum. The analysis also discloses that raising the diffractive efficiency is the next step for us to take.

On the basis of Fresnel diffraction theory, surface microstructure of diffractive optical element (DOE) based on sphere using for aspheric surface was presented in this paper according to the same performance of introducing aspericity into optical system. Spherical DOE uses sphere taking the main focusing power and diffractive microstructure compensating the phase difference from aspheric surface to reference sphere. Thus, spherical DOE has the advantage of avoiding the difficulties of fabrication and measurement of aspheric surface and constructing the DOE microstructure in larger range than the DOE based on planar surface with the limitation of the critical dimension. An important aspect of this method is how to obtain the best fitting reference sphere to aspheric surface. The reference wavelength and the critical dimension were introduced into the limiting condition as the choosing criterion of the best fitting reference sphere. With this method all the lens surface of optical systems can be fabricated as sphere. The theory and method was proved and emulated with computer. Microstructure DOE based on sphere as substitution for aspheric surface is feasible in practice.

In-line holography is a simple way for small object imaging. The Gabor transform is used for object characterization directly from in-line holograms. Three-dimensional locations of an object can be determined from the Gabor transform spectrum of its in-line hologram. The relationship between the Gabor angle and the location of the object is established, Computer simulations and experimental result have been presented to demonstrate the validity of this method for object charactering. The promising application of this method is particle field analysis.

In the Fresnel condition, the design and optimization method of binary optical element with multi-focus has been investigated. A one-step optimizing algorithm of tilted multi-focus diffractive optical element is presented by using a tilted image plane in the Fresnel approximation. Based on iterative Fourier transform algorithm (IFTA), not only the higher diffraction efficiency, increased about four percent, but also the instability of distributing at the different focus, namely different tilted angle, are obviously improved by the modified simulated annealing algorithm (SA). Comparison on one-step and multi-step circle algorithm of optimizing multi-focus diffraction element shows both the faster speed and the higher diffraction efficiency for the one-step algorithm.

The fabrication of multilayer dielectric gratings was theoretically and experimentally investigated. The RCW (rigorous coupled-wave) method was adopted to theoretically analyze the influence, which is caused by the gratings profile and multilayer dielectric stack, on the diffraction efficiency. Researches on detecting principle and methods of the multilayer dielectric gratings were also tried to be carried out here. The spectral distributing of the zero order diffraction efficiency was used to judge the gratings profile, basing on the theoretical research and the calculating results by the RCW method. Detecting experiments have been conducted to compare the theoretical analyses; the results of this comparison may be helpful to instruct the detection of the gratings profile.

A new fast algorithm using the “host” Fresnel zone plate was proposed to improve the computational efficiency of computer-generated hologram (CGH) for 3D objects. By reading .3DS files, the spatial position information of each point of the 3D object was obtained directly. With the illumination of plane wave, the “host” Fresnel zone plate of a single point could be equal to all points located in the same depth plane - as the Fresnel zone plate was translated and superimposed along the horizontal and vertical axes. Consequently, the hologram of a 3D object could be built up by superimposing different Fresnel zone plates in the corresponding depth planes. For a digital object composed of 1060 points, it cost about 83s to generate a hologram of 1024*768 pixels. The CGH of 3D objects with the results of the reconstruction was presented in this paper, which proved the feasibility of this algorithm.

This paper studies the fabrication of the nano-scale grating using laser beam interference. The beams come from a He-Cd laser @442nm were interfered with each other inside a prism, and form the interference pattern on the photoresist layer that coated on the bottom of the prism. The method can fabricate gratings with period that less than the half of the wavelength of the interference laser beams. It becomes a promising process that can fabricate a grating with periods of 160nm without using UV light source. The experimental result is also demonstrated.

A simple holographic 3D photonic crystal fabrication system is presented. The key element in the system is a HDOE made with holographic approach. The HDOE can generate four beams with single illuminating beam to form a 3D interference pattern. The incident angle of the outer beams and beam intensity ratio of the central beam to the outer beam can be adjusted in HDOE fabrication process. Computer simulation demonstrates that to obtain properly connected lattice structure in photoresist, beam intensity ratio and exposure dosage must be considered simultaneously. Experimental result has verified the effectiveness of the technique.

Integration of micro-optical elements (MOEs) with optical fiber at top-end was realized by use of focused ion beam (FIB) direct milling. The designed MOEs (micro-refractive lens, micro-diffractive lens with continuous relief, and micro-gratings) were directly milled by the FIB with ion energy and ion beam current of 40 keV and 569 pA, respectively, in the core area of both single mode fiber and multimode finer for dispersion and focusing uses. The integrated fibers can be used in microspectrometer, optical fiber sensors, and micro-optical systems for biochemistry analysis.

Utilizing the in-situ monitoring scheme, we obtained the relationship between diffraction efficiency and etching time under different ion beam conditions. Since the distribution of photoresist is found to be changing innegligible during etching and causes difficulties in determining the end-point, it becomes necessary to consider the photoresist effect on the diffraction efficiency. Taking into account the influence of the etch ratio of photoresist to hafnia, we simulated the efficiencies of the reflected -1st-order diffraction (-1st-order Littrow mount, λ=1064nm, TE polarization) as functions of etched depth. Though the midway evolution of the grating profile is complicated, the main features of the simulated curves agree very well with those of the experimental monitoring curves. With this knowledge, by in-situ monitoring the diffraction intensity, we can obtain good estimates of the etched depth and the erosion progress of the photoresist mask, which are of great help to determine the etching end-point and suitable working parameters of the etcher, and so as to achieve much better cost-efficiency. Employing the proposed in-situ monitoring scheme, multilayer dielectric gratings with retroreflected efficiency approaching 100% were fabricated.

Ronchi gratings are widely used as beam splitters in interferometry. The phase Ronchi gratings are fabricated in K9 (or BK7) substrates using a photolithographic process and ion beam etching process. The geometry of the gratings was determined within the approximations of the scalar diffraction theory to minimize their diffraction intensities in 0 and 2 orders at 514.5nm. Their diffractive characteristics are measured using Ar+ laser at 514.5 and 496.5nm. The phase Ronchi gratings exhibit the diffraction intensity in 0 or 2 order to be three orders of magnitude less than that in 1 order. Soft x-ray condenser zone plates are one of the most essential condensing and dispersing elements in the field of soft x-ray microscopy. The zone-plates are used at 3.2nm, whose diameters are 2.8mm. The widths of their outermost zone are 647nm. The zone plate is made of Au. Self-supporting zone plates are fabricated by holography-ion beam etching process to obtain x-ray lithography mask, the x-ray lithography, photolithography and micro electroplating process were used to obtain their self-supporting structure. The self-supporting zone plates are free of membrane absorption and degradation.

In order to realize the fabrication of binary beam shaping element with complex phase structures, a new method of making the relief phase structures under the dot-by-dot exposure mode is presented by using laser direct writing (LDW) system with the square-spot. The size of the square spot obtained with the projection optical configuration is set to match with the minimum phase unit which lead to exposure mode can be easily controlled. The diffraction properties of the phase unit structures etched with single Gaussian spot and square spot are discussed. The binary beam-shaping elements with two-steps by square-spot exposure have been achieved to 31.0% +1 order diffraction efficiency. The experimental results are given.

Holographic and ion beam etching technique has become routine means for fabricating vacuum ultraviolet and soft x-ray diffraction gratings. A novel technique has been successfully, in which oxygen reactive ions etching was used to achieve resist ashing of the grating, to fabricate diffraction gratings with holographic ion beam etching. The new technique was used to fabricate a spherical blazed grating, 1200g/mm and 130 nm blazed wavelength, and some laminar gratings for monochromators in the beamline of National Synchrotron Radiation Laboratory. The results show that the new technique can considerably lower the stringent requirements of holographic exposure and development, and makes it controllable to make smooth grooves with desirable depth and duty cycle. A gold transmission grating is one of the critical elements in the soft x-ray spectrometer for plasma diagnostics. With holographic-ion beam etching technique, a number of self-supporting transmission gratings have been fabricated for inertial confinement fusion (ICF) diagnosis.

A wave aberration compensation method for optical system and human eyes has been studied. The wave distortion of the human eye can be measured using a Shack-Hartmann sensor and described in an eight-order Zernike polynomial. By picking up the higher order’s terms of the wave aberration from the measured polynomial, characteristics of the higher order wave aberration were analyzed and concluded. The conjugate phase plates were designed based on the distribution of the single and the overall wave aberration of the eye. The thermal-filtered halftone mask technique is developed to manufacture such an abnormity micro-optical structure. The compensators for the single or the overall wave aberration were fabricated respectively. The relief profiles were evaluated using both three-dimensional profiler and interferometer. A primary experiment for compensating the higher-order wave aberration of an artificial eye was demonstrated.

Using holographic recording technology, two kinds of transient diffraction gratings were demonstrated in azo-dye doped Poly(methyl methacrylate) (PMMA) films and bulk matrices respectively. In PMMA films containing azo-dye Disperse Red 13 (DR13), the refractive index gratings came from the reorientation of azo-dye molecules in different areas with different polarization distribution of recording beams. The characteristics of the transient gratings in films samples which were recorded by two mutually parallel polarization beams (PP and SS) as well as orthogonal linear polarization beams (PS and ±45°) from an Ar ion laser (514nm) were investigated by monitoring the first order diffraction intensity of the readout He-Ne laser beam (632.8nm). With the interaction of bi-photonic lights at 514nm and 632.8nm, the transient gratings in azo-dye DR13 doped PMMA bulk matrices was a kind of population gratings of Trans and Cis isomers, which was attributed to the weak absorption of Cis isomers at 632.8nm and the positive dichroism of Trans isomers at 514nm. Furthermore, the all-optical switching behavior of the two kinds of transient holographic gratings were observed repeatedly by turning on and off the writing beams, and a response time at the magnitude of ten milliseconds order could be obtained.

This paper has put forward a kind of new circular holographic grating manufacture method. Have described the basic principle and concrete light way in detail. Have analyzed interference field and provided the formula of intensity of light of distributing. Provide the experimental result, has discussed the reason for producing the error.

Doped 0.5mol% Er₂O₃ and (2,4,5,6)mol% MgO in LiNbO₃ crystal, Mg:Er:LiNbO₃ crystals were grown by Czochralski technique. The IR transmission spectra of those crystals were measured. The OH^- absorption peak of Mg(2mol%):Er:LiNbO₃ and Mg(4mol%):Er:LiNbO₃ at about 3486 cm^-1,while that of Mg(5mol%):Er:LiNbO₃ and Mg(6mol%):Er:LiNbO₃ at about 3535 cm^-1. The shifting mechanism of OH^- absorption peak was discussed based on the Li-site vacancy model. Using m-line method tested the photodamage of Mg:Er:LiNbO₃ waveguide substrate. The photodamage resistant ability of Mg:Er:LiNbO₃ is higher than that of Er:LiNbO₃. The photodamage resistant ability of Mg(5mol%):Er:LiNbO₃ waveguide substrate improves two orders than that of Er:LiNbO₃.

The theory and the method of digital holography and its application have been studied, and part of the study results mainly involving eliminating zero-order diffraction in digital off-axis holography, analysis of the influence factors of the reconstructed image quality, particle field measurement, etc. are reported, and the experimental results are also given. The preliminary investigative basic research in color digital holography has been done. Multiple-wavelength recording system is introduced in digital holography, and recording of hologram by CCD is no longer a single wavelength one, which is a beneficial tentative research for the development of color digital holography. The research and the results provide the initial theory and experimental basis for the further advancement of digital holography.

A numerical compensation technique is proposed to enhance the quality of reconstruction of phase-shifting lensless Fourier digital holographic microscopy. Introducing phase-shifting technique into the in-line lensless Fourier digital holographic microscopy is widely used, because this system possesses high resolution and is able to suppress the zero-order of diffraction and the twin image in reconstruction. Practically, it is likely to suffer from the lower resolution due to the blurred image in reconstruction plane in respect that the normal of object plane is not perpendicular to the CCD plane or the distance between the source of reference wave and the CCD plane is not equal to the distance between the object plane and the CCD plane accurately. Mechanical adjustment has difficulty in achieving high accuracy of adjustment and needs a great deal of time. Based on the theories of Fresnel diffraction and holography, it is found that numerical compensation can complete adjustment in high accuracy. It uses chirp function as compensation factor. The values of the three compensating parameters in three directions are obtained by repeatedly applying the numerical reconstruction procedure through gradual approach until the best in-focus image is obtained. The precisions of the three compensating parameters are decided by requirement. The main advantages are: (1) the accuracy of adjustment is high, (2) the quality of reconstruction can be greatly improved. In order to testify the feasibility of the numerical compensation technique, experiment is carried out. Its results show that fine numerical compensation is necessary to advance the quality and resolution of reconstruction.

We propose a new method of digital watermarking with double binary optical phase encoding technique. Design procedures base on iterative Fourier transform algorithm (IFTA). The combination of two binary phase structures, in which one is used to encode the hidden image, and the other as encryption phase key, is inserted as watermark into the host image. The affections of phase levels of binary phase holograms on the quality of extracting watermark from the watermarked image have been analyzed, and results show that the 2/2 phase level combination is the best scheme of watermarking than other multiple combinations. The principle of encrypting the private key has been presented. This method can effectively increase the security of digital hologram watermarking and support the hard output of the watermarked image. The watermark is robust against hard output. We analysis the influence on the quality of extracted image after the processing of printing and scanning. We also develop the software tool for the watermarking process. The experimental results are given.

Organic-inorganic nanocomposite films were prepared by dispersing an aromatic methacrylic monomer and a photo-initiator in organic-inorganic hybrid sol-gel matrices. The film properties could be controlled by optimizing the content of an organically modified silica precursor (TSPEG) in the sol-gel matrices. The photopolymer film modified with the organic chain (TSPEG) showed high diffraction efficiency (>90%) under an optimized condition. In addition, we implement a digital holographic security system that combines the electrical biometrics technology with fully digital holographic storage using an organic-inorganic hybrid type photopolymer film.

The simple hologram recording system of digital off-axis holography is designed. Holographic diffraction grating of low spatial frequency is introduced to digital holography, acting as a beam splitter, illuminated by the monochrome plane parallel light wave, and the three different plane parallel light waves, namely, the zero-order and the ±1order diffraction waves, are generated. An off-axis holography system is configurated between the +1/-1order diffraction waves and the zero-order wave. The theoretical analysis has been done in detail and the zero-order diffraction in the reconstructed image of digital off-axis holography is also analyzed theoretically. The experimental results are given. The feasibility of the experimental system presented in this paper was confirmed, simple in optical structure and easy in operation. In addition, the zero-order image can be eliminated by numerically processing the holograms of object with different recording parameters obtained by adjusting the reflecting mirror in the recording optical system to vary the incidence beam orientation in CCD to introduce a phase shift.

The transformation properties of dynamic hologram recorded in a quadratically nonlinear material are considered for the general case when the frequencies of object and reference waves are essentially different. The expressions are deduced that determined the wavelength of the reconstructed wave and directions of propagation of the rays of light that form the image. An experiment is carried out on the base of a noncollinear scheme of nonlinear interaction. A hologram was recorded in a KTP crystal by the light of a YAG:Nd laser (λ = 1.064 μm), the width of the pulses being 300 ps. The frequency of the object wave was shifted due to the Raman scattering in a crystal Ba(NO₃)₂. The values of the frequency shifts were Δν, 2Δν, 3Δν (Δν = 1047 cm^-1). Each of the shifted in frequency component formed an image of the object whose resolution was close to the diffraction limit. All these components were separated in space. The value of separation was in a good agreement with the predictions of the theory. It was stressed that the inertialess nature of a hologram of such a type makes it possible to use them for ultrafast communication of signals in optical communication lines.

By employing new types of multi-color photosensitizers and photochemical promoters to photo-crosslinking gelatin system, a high-quality single-layer panchromatic dichromated gelatin material is achieved for color holography. Some preliminary results of spectral response, photosensitivity, and spectral selectivity are reported in this paper. Using red, green and blue lasers, namely three primary colors, the bright volume transmission and reflection holograms can be recorded successfully on the panchromatic material at the exposure level of 30 mJ/cm². It can be expected to have practical applications in the fields of true-color display holography, wavelength multiplexing holographic storage, and holographic optical elements.

In this report, a method to make a cartoon hologram was introduced. Based on the principle of multi-slits rainbow holography, two positive films having different moving states can be synthesized to create a stereo-effect cartoon hologram. The taking processes were given. The dependence on the distances for two slits, slit image and eyes were discussed.

The diffraction characteristics of the volume holographic gratings made by multi-exposures with angular multiplexing during its construction is investigated. Because of the reflection by the interface between the emulsion and the substrate or the air there is an extra unslanted periodic structure inside a slanted grating, it will affect properties of the slanted volume holographic gratings. When the angle between the surface of the substrate and the grating plane of the slanted grating is less than a certain value, an extra peak accompanying the main peak will appear in the diffraction spectrum. But, when the angle is larger than the certain value, one designed and expected main peak will disappeared while the extra peak is kept and observed. This phenomenon limits the capacity of the volume hologram for the application in wavelength-division multiplexing (WDM).

Volume holography is promising for devices such as wavelength filters. However, in previously reported work with these holographic devices the diffraction efficiency and wavelength selectivity were not so satisfactory, which affected the insertion loss and channel spacing of the device respectively. In order to investigate the performances for most of the volume holographic devices which are of finite size and with 90 degree geometry, two-dimensional (2-D) coupled-wave theory is more accurate than that based on the well-known Kogelnik’s coupled-wave theory. In this paper a close-form analytical solution to 2-D coupled wave theory for 2-D restricted gratings is presented firstly. Then in order to achieve the optimum insertion loss and channel spacing for dense wavelength division multiplexing (DWDM) filters, diffraction properties, especially effects of the grating strength and grating size ratio on the peak diffraction efficiency and wavelength selectivity are researched based on the 2-D coupled-wave theory and its solution. The results show that this solution is capable of design optimization of volume holographic gratings for various devices, including wavelength filters. And the design optimization is given in order to gain the optimum peak diffraction efficiency and wavelength selectivity. Finally, some experimental results showing the angular selectivity for different grating size ratio are given, which agree well with the 2-D coupled-wave theory.

When a volume hologram grating is illuminated with a femtosecond laser pulse, its diffraction is crucial for practical application. In this paper, an analytical expression is given to calculate the diffractive spectrum of a transmission volume hologram grating illuminated by an ultrashort laser pulse. Numerical simulation shows that it is possible to achieve a large enough diffraction bandwidth of volume hologram grating in frequency domain for the bandwidth of 50-fs pulse for frequency-domain femtosecond pulse processing when the modulation index is properly selected. Furthermore, we predict that the diffractive spectrum can be controlled by tuning the modulation index of the volume hologram grating. Especially, the diffractive spectrum of the central wavelength is totally suppressed for some specific modulation index. Finally, we study the influence of loss on the diffraction efficiency of the volume hologram gratings. We found that, except decreasing the diffraction efficiency intensity, the presence of loss has little influence on the diffraction pattern. These novel results suggest that, by carefully designing the volume hologram gratings, it has great potential for the processing of the femtosecond pulses in the Fourier domain. An advantage of this present scheme is the flexibility and possibility of using the volume hologram grating to implement dynamic processing, with a potentially higher efficiency than by use of holographic thin films.

The theoretical model of a photorefractive optical switch, which is implemented by adjusting the wavelength and space-phase of the read-out beam to control the diffraction direction of volume grating in a photorefractive crystal, is proposed. For N channel optical switch, each channel include n dissimilar wavelength carrying information with distinct space-phase, and any wavelength can turn into any other N-1 channel controlled by space-phase. In order to obtain this device, multiple holograms be recorded in a photorefractive crystal, performing an optical database accessible either by wavelength or by space-phase multiplexing. The holograms were written in a Fe doped LiNbO₃ using an Ar⁺ laser with its three wavelength. The diffraction direction depended on wavelength and space-phase of the read-out beam, which agrees with the theoretical prediction and indicates that photorefractive crystal possesses excellent optical switching properties. It is demonstrated that the diffraction direction of the volume grating is relevant to the wavelength and space-phase of read-out beam; this property can be used to implement the all-optical switch.

We proposed a new model to analyze Bragg selectivity of volume holograms in spatial domain as well as in temporal domain. The applications of volume holographic filters to surface variation detection and high dense wavelength filtering are presented.

In this paper, a very effective recording technique of optimal recording/fixing switching time induced by high-coupling effect is considered for high diffraction efficiency of local nonvolatile holographic gratings in LiNbO₃:Ce:Cu crystals. The fixed diffraction efficiencies gained by optimal switching time are up to 100% in theoretical simulations and 78% in experiments. It provides a new idea to obtain high persistent diffraction efficiency. Finally, as one of examples for design of 3-D optical integrations by local nonvolatile holographic gratings, a new type of volume holographic grating lenses for converting a plane wave to a lateral-spread spherical wave and vice versa, is illustrated.

Taking the reflectance phase volume hologram as an example in this article, we calculated the diffraction efficiency in H. Kogelnik’s theory after modifying the cosine term of medium parameter in H. Kogelnik’s theory as a nonlinear term again, and get the influence on the diffraction efficiency of recording medium nonlinear photosensitive properties.

The holographic properties of doubly doped lithium niobate crystals with Indium have been investigated. It is found that doping slight Indium concentration (0.5mol%) in LiNbO₃:In, Fe crystal can efficiently increase the sensitivity with small dynamic range changing. To improve the whole holographic properties of LiNbO₃ crystal, LiNbO₃:In, Fe with ideal doping concentrations and a new photorefractive material LiNbO₃:In, Mn have been proposed and achieved larger dynamic range, higher sensitivity and better signal-to-noise ratio than LiNbO₃:Fe crystal (Fe:0.03wt.%) that is generally considered as a preferable storage medium in holographic memories. In a common volume of LiNbO₃:In, Fe crystal proposed, 2030 holograms have been successfully multiplexed and exactly identified in a compact volume holographic data storage and correlation recognition system.

According to speckle modulation on the object beam of a volume holographic correlators, we show that the sidelobes of the correlation patterns along the vertical direction as well as those along the horizontal direction are well suppressed, so that the multiplexing space is markedly reduced and the channel density is largely increased. The experiment of 2030-page human faces correlated storage and recognition are presented, a very clear correlation spots array is achieved, and the recognition accuracy is better than 95%.

Self-enhancement effect and oscillatory characteristic of diffraction are observed during the holographic recording in LiNbO₃:Ce:Cu crystal. Both phenomena are owing to the dynamic diffraction characteristics of photorefractive volume holograms or gratings. On the basis of the experimental results and the above concept, two methods, i.e., the self-enhancement effect and the optimal switching from the recording step to the fixing step, are correspondingly suggested for the production of persistent holograms with high fixed diffraction. By use of our recently presented time-space dynamic theory of two-center holographic recording, the experimental results are theoretically analyzed and numerically simulated. The simulations are in good agreement with the experimental results. It is shown that the self-enhancement in both steps of recording and fixing can obviously enhance the recorded and fixed hologram and thus the nonvolatile diffraction efficiency. And it is also indicated that switching after the first diffraction maximum leads theoretically to fixed diffraction of as much as 100% with a suitable switching time. This optimal switching provides a completely new method to obtain high persistent diffraction of the nonvolatile holographic storage in doubly doped LiNbO₃ crystals.

The distributing formulas of the complex amplitude and the light intensity at output plane are presented in this paper, based on the new method using micro-optical array structure to achieve Perfect Shuffle (PS) transformation presented by us, using the theories of information optics and binary optics. According to the formulas, the technical design and fabricated parameters are completed and exported. It’s indicated that the theoretical analysis and designs accords well with practices in the sequent fabrications and testing experiments. The conclusions of the theoretical analysis in this paper are very important and significative for guiding the realization of optical switching and optical interconnection by using micro optical structure with the diffractive method.

We examine and characterize a wavelength demultiplexer using a holographic grating for WDM multiple-channel applications. The holographic grating is a kind of volume grating recorded in a photopolymer, which is different from the general surface relief type diffraction gratings. The holographic grating disperses the wavelength components of incident wave into spatial domain so that through the coupling optics, different wavelength channels can be separated to the different output optical fibers. The characteristics of the polymeric holographic grating are compared to those of the relief type diffraction gratings. Overall demuliplexer characteristics is characterized by applying first order Born approximation with electro-magnetic vectorial analysis. It shows that the amplitude and group velocity (i.e., the chromatic dispersion) characteristics are determined by the holographic grating phase structure and out-coupling optics lens aberrations. The out-coupling lens aberration effect to the chromatic dispersion is examined and classified according to the lens aberration classification. The holographic grating phase perturbation (i.e., chirping) can be used to minimize the lens aberration caused chromatic dispersion to improve the demultiplexer performance. The demultiplexer polarization dependent loss is also examined in relation to the spatial dispersion and diffraction efficiency characteristics.

We describe the generation of shaped femtosecond multiple pulses by using the phase-only filters designed with optimized techniques, which includes Dammann-type filter and another filter of producing specific unequal-spacing and equal-intensity. We consider the influence for the output pulses with the accuracy of the transitional points, the number of pixels of the mask, the periodic repetition number for the Dammann-type gratings, and the change of the Gaussian spectral phase of the modulated phase plate with the wavelength. On the other hand, experiments of ultrafast temporal pattern recognition by the frequency-resolved optical gating (FROG) characterization technique are also given.

Talbot self-imaging effect and fractional Talbot effect of a grating under illumination of monochromatic continuous wave is an important basic diffraction phenomenon, and has been extensively studied. In this paper, we studied the Talbot self-imaging effect of gratings that was illuminated by femtosecond pulse. Femtosecond laser beam is not monochromatic but includes a broad range of spectrum distribution. In this case, observed optical field in the output plane can be regarded as a coherent superposition of the contribution from each frequency component. Based on this assumption, we study diffractive characteristic of femtosecond pulse, and we theoretical analyse the intensity distributions with Fresnel diffraction formula behind a grating under illumination of a femtosecond pulse laser. Intensity distribution on the Talbot imaging planes are obtained, which show that Talbot images of femtosecond pulse are not the same as that under continuous wave illumination. At the same time, experimental results are in good agreement with the theoretical analysis. Rectangular amplitude gratings with different periods (200 μm and 80 μm respectively) were illuminated by an expanded femtosecond pulse laser, and the Talbot images are obtained by using a CCD camera at different Talbot distances. Experimental results demonstrate that the femtosecond pulse laser can cause a large distortion of Talbot images (including the contrast of imaging and the decrease of diffraction efficiency), compared with that under continuous wave illumination. In addition, increasing of the Talbot distance can also result in distortion of a Talbot image. The theoretical and experimental results are helpful for further applications of the Talbot effects under femtosecond pulse illumination.

In this paper, a binary optical array element which can realize 8-channel PS transformation is fabricated with very large scale integration (VLSI), stepping photolithography and reactive ion etching (RIE). Using the element, we perform experiments of the PS transformation, tests and analysis. The efficiency and cross talk of each channel are measured when only one channel has been reserved while other channels have been closed. The result indicates that the method proposed to realize the PS transformation by using the micro-optical array element agrees well with theoretical expectation. This success of the experiment lays a good foundation for us to do further research on optical transformation through multilevel interconnection.

Integral imaging is one of the attractive autosteroscopic three-dimensional (3D) displays. The 3D image can be composed by integrating elemental images with different perspectives. Due to the geometry of integral imaging system, pseudoscopic imaging is an inevitable problem regardless of image type such as imaginary and real. Various methods are presented to improve the image quality and viewing parameters but few of trials for solving pseudoscopic imaging problem are presented. We propose and compare two methods for orthoscopic 3D real image reconstruction in integral imaging system using elemental image transformation. Theoretical analyses of elemental image transformation for 3D real image reconstruction are described in details and the experimental results are presented.

A three-dimensional (3-D) imaging configuration with a holographic scanner and two auxiliary reflectors is discussed, which employs a Nd:YAG laser that operates at a wavelength of 1.06 μm. Compared with traditional scanners, holographic scanner has many advantages, such as smaller in size, lighter in weight and simpler in structure. The data collected are stored into a 3-D array of 8-bit intensity values and displayed in two ways, a 2-D intensity image or a 3-D image. The 3-D image is displayed on the screen of a computer according to the perspective transformation technology of coordinates.

In this paper the research of the real-time three-dimensional holographic imaging system which uses liquid crystal panels to display the computer generated Fresnel holograms for reconstructed 3D images is described. The reconstructed effects are related to each step of the process and the characteristics of the devices. The contradictions between the quantization of holographic numerical data and the properties of the display device are the important reasons for the reconstruction errors. A new algorithm for calculating point holograms is proposed for reducing the reconstruction errors. Finally the original experimental result is given.

The theoretical and simulation angular dispersion characteristics of phase-only diffractive element are presented. The multi-wavelength dividing element is a key element in WDM system. Phase-only diffractive optical element (PDOE) used as WDM element has many merits, such as easy coupling, polarization insensitivity, low cross-talk and simple structure. There are two problems should be paid attention to in the design of PDOE. Firstly, the required large dispersion comes along with large diffraction angle. So the Fresnel assumption can not be satisfied in the diffraction calculation. Secondly, in the design of the PDOE, the multi-wavelength Yang-Gu phase retrieval algorithm is utilized to optimize the angular dispersion of PDOE. The convergence of YG algorithm is highly sensitive to the destination value. With the motivations above, it have been proceeded the study of the angular dispersion of PDOE. The theoretical and simulation results are presented in this paper. Based on the Phase Binary Equation, the angular dispersion is analyzed. Latter in this paper, an example PDOE has been designed. In the design process, the convergence of YG algorithm has been assured by the destination value carefully selected based the analysis results of angular dispersion. In the last part of this paper, the diffracted optical field behind the designed PDOE has been simulated with the method of Rayleigh-Sommerfeld diffraction theory. The simulation results are in quite accordance with the analytical results. So the angular dispersion of PDOE has been presented and validated by the works in this paper.

The design of a phase-only diffractive WDM element, based on vector theory, is demonstrated. The adopted method of this design is a rigorous method based on the rigorous electromagnetic computation models the Beam propagation method (BPM)., Rayleigth-Sommerfield diffraction theory, and iterative optimization method. This phase-only diffractive optical WDM element (PDOE-WDM) is motivated by the intersatellite optical communication (IOC). And the motivation also raises the demands of large numerical aperture, polarization insensitivity and high diffraction efficiency. In order to predict the phase filter of DOE and the large angle diffraction precisely, a vigorous vector method has been adopted. The complex optical field right behind the BOE is computed by the Beam propagation method (BPM). And the diffraction between the back side of DOE and focusing plane is computed by the means of Rayleigth-Sommerfield (RS) diffraction theory, a more rigorous diffraction theory than Fresnel diffraction theory. The vector BPM method and the RS diffraction theory combined with FFT technology come along with the improvement of PDOE-WDM performances. And the high performance PDOE-WDM will play an important rule in IOC to increase communication rate as well as decrease volume and weight.

Diffractive optical element (DOE) is a proposing technique to realize beam smoothing in inertial confinement fusion (ICF) system. In indirect-driving ICF system, beam smoothing is required on a certain inclined plane non-perpendicular to the optical axis. In this paper, the DOE is designed to be consistent with beam smoothing with long focal depth, which ensures that the beam smoothing can be obtained on the inclined plane. And in the optimization, the sampling interval is chosen as half of the traditional sampling interval, in order to realize true beam smoothing distribution. The simulated results show that the performance of the beam smoothing can be held with any sampling interval on the inclined plane. Finally, the performance of the DOE is quantitatively analyzed. Two parameters, light efficiency and top non-uniformity, are re-defined. These two parameters can truly and exactly evaluate the performance of the DOE, because their definitions can go back to the origin. The simulated results show the validity of the design with long focal depth and half of the traditional sampling interval.

A novel design method of diffractive optical element for shaping Gaussian Schell model beams is investigated. In the design, it is important to solve a deconvolution problem for obtaining diffraction image with edge-sharpness degraded by the convolution effect of the partially coherent Gaussian Schell model beam. In this paper, a simple heuristic approach to the deconvolution problem is addressed. It is shown that an extra rim pattern around the target diffraction image can lighten the unwanted edge-blur of the diffraction image. The algorithm for generating the extra rim pattern is explained.

It is important to have a tunable encoder in optical channel coding for the purpose of coping with varying communication environment. In this paper, a tunable encoder based on the holographic grating (HG) using photopolymer as the holographic medium is described. The system is composed of photopolymer holographic grating as a demultiplexer, spatial light modulator (SLM), and other lens systems. The photopolymer grating acts as a demultiplexer to distribute optical wavelength channels on the SLM through its spatial dispersion property. Then, the SLM produces wavelength-endcoded data but its spatial amplitude/phase modulation. The merits of using the holographic grating are that it has relatively easy fabrication process, and that non-uniform grating structure and multiplexing can be exploited. In this setup, we can additionally change demultiplexing wavelengths by inducing strain gradient on the polymer grating, which is attached on the two XYZ linear stages. Hence a different set of wavelengths is incident to SLM and this enables another type of encoding pattern.

As a portable device, such as PDA and cell phone, a small size build in virtual input device is more convenient for complex input demand. A few years ago, a creative idea called 'virtual keyboard' is announced, but up to now there's still no mass production method for this idea. In this paper we'll show the whole procedure of making a virtual keyboard. First of all is the HOE (Holographic Optical Element) design of keyboard image which yields a fan angle about 30 degrees, and then use the electron forming method to copy this pattern in high precision. And finally we can product this element by inject molding. With an adaptive lens design we can get a well correct keyboard image in distortion and a wilder fan angle about 70 degrees. With a batter alignment of HOE pattern lithography, we’re sure to get higher diffraction efficiency.

This paper concerns on the Optical Transfer Function (OTF) of confocal fluorescent microscope in laser scanning microarray system. The cut-off of confocal microscopy, the lateral and the lognitudinal resolution, and the relationship of pinhole and resolution were discussed in a novel method. At the same time, all of these parameters of confocal microscope in microarray system are compared with other conventional and coherent microscope. The results obtained in this paper are significant for selecting the appropriate parameters and evaluating the properties of a confocal scanning fluorescent microscope for microarray reader system in order to improve the performance.

It is presented here that the all-digital holography is applied to the digital image hiding. Computer Generated Hologram is generated and reconstructed by numerical method. The secret message and the host message are all still gray-images. The secret image is first transformed into a hologram (CGH), which is called holographic transform and then Arnold transform is performed. DCT is applied in the host image. Then the secret image is embedded into the DCT middle coefficients. The application of the holographic transform improves the transparency of the secret image; by controlling the parameter of the hologram the secrecy of the image is enhanced and add another key to have invisibility and certain robust.

We present a simple technique for hologram multiplexing to handle images imposed on different polarization states simultaneously, where light of randomly distorted wavefront and randomly disarrayed polarization is deliberately exploited as a reference light. Such randomly blurred light is generated in succession by a rotary movement of a bundle of optical multi-mode fibers. We show that the direct use of light passing through the fiber bundle contributes to improve the storage capacity of previous hologram recording systems in which a polarizer has been employed with a fiber bundle in rotary movement. Since the actual wavefront patterns provided by fiber bundles are not completely random but quasi-random, a theoretical investigation on the performance of hologram multiplexing is carried out with numerically created quasi-random patterns prior to an experiment. In the end, we perform the experiment of hologram multiplexing for the validity of our approach.

Optimization of performance of holographic gratings was investigated by changing the chemical structures of photopolymerizable monomers, the LC content, and recording beam intensity, which strongly related to the control of kinetics of polymerization and phase separation of LCs. High diffraction efficiency was obtained using 3-acryloxypropyltrimethoxysilane (APTMS) and 2-[(3,4-epoxycyclohexyl)ethyl]trimethoxysilane (ECTMS) as siloxane-containing reactive diluent by inducing a fast and good phase separation originated from the incompatible and flexible properties of siloxane chain even at a very low LC concentration (10~25wt%), in contrast to the case using diluent without siloxane component, like N-vinylpyrrolidinone. The phase-separated morphologies of gratings, such as spacing and surface topology, were observed by atomic force microscopy (AFM). Very regular and smooth morphologies were observed for the formed holographic gratings with APTMS and various amounts of LC.

A novel device and corresponding techniques are proposed, which are the transverse element of binary optics and transverse-adding technique. The transverse-adding technique of binary optics can be used to fabricate microelectronic elements and micro-mechanical elements very well. By using this technique, the micro-photoelectric-mechanical systems can be integrated on a single chip. The fabrication model and method of Fresnel diffractive lens with Transverse-adding technique are presented. It is demonstrated that the diffractive efficiency of Fresnel diffractive lens fabricated with this technique can reach 100% by theoretic analysis. In addition, the diffractive efficiency of this kind of Fresnel diffractive lens is independent of technique error.

Angular selectivity of volume grating limits the capacity of holographic 3-dimensional storage. In this work, we investigated experimentally the influence of wavefront shapes of the writing beams on the angular selectivity of thick grating in a LiNbO₃ crystal. The experimental results showed that longer wavefront curvature results in more critical Bragg angular selectivity.

We demonstrate a method to fabricate varied-line-spacing grating by employing elastic medium with variable vertical section. The advantages of this technique include continuous diversity of variation of line-space, high fabrication efficiency and low cost, etc. It is very difficult or unrealizable to produce this variation of line-space by traditional interference lithography. This kind of grating can be used in the optical position sensor and it can improve the precision of the sensor.

The problem of designing a diffractive optical homogenizer that produces an annular uniform intensity beam from a spatially variable and partial-coherent source such as excimer is considered. A modified target pattern which corresponds to full-coherent field is presented to ensure the homogenizer can work well in partial-coherent field generated by excimer. Because modified target pattern is proportional to the deconvoluation between ideal target pattern and slit function, to avoid the mathematical puzzle of deconvolution, an artificial modification on target pattern is proposed and good numerical results are produced. After dividing the homogenizer into several sub-elements with proper numbers, we find it is quite insensitive to the amplitude fluctuation of input field. With our method, the homogenizer is possible to be used in partial-coherent and fluctuant field.

The congruent Fe (0.03%wt):LiNbO₃ crystals doped with different concentration of MgO (0, 2, 4, 6 mol%) were grown by Czochralski method in air atmosphere. The ultraviolet-visible absorption spectra, infrared absorption spectra of the crystals were measured in order to analyze their structure. The absorption edge of the Mg: Fe: LiNbO₃ crystals shifted to the ultraviolet band compared with that of Fe: LiNbO₃. The OH^- absorption peaks of I and II crystals located at about 3483cm^-1, while those of III and IV crystals shifted to 3536cm^-1. The mechanism of OH^- absorption peak shifting was studied. The light scattering ability resistance of Mg: Fe: LiNbO₃ crystal was observed by straightly observing transmission facula distortion method. It indicated that light scattering ability resistance of III crystals was three orders of magnitude higher than that of Fe: LiNbO₃ crystals. The exponential gain coefficient, diffraction efficiency and respond time of Mg: Fe: LiNbO₃ crystals were measured by two-wave-coupling technology. The results indicate that exponential gain coefficient of Mg: Fe: LiNbO₃ crystal was almost four times as that of iron-doped LiNbO₃ and the response time exhibited four times shorter than that of iron-doped LiNbO₃. Furthermore, the dynamic range was also calculated by the expression: _M # = (τ_e ∠√η)/τ_ω. The results indicated that Mg (4 mol%): Fe:LiNbO₃ was the most proper holographic recording media material among four crystals in the paper.

In photorefractive holographic storages, the superimposed holograms make the refractive index of the media irregular. The readout beam is scattered by the media and the noise is added onto the reproduced messages. In this paper, we introduced a simple way to suppress the noise caused by the superimposition. In our method, holograms were recorded by convergent reference beam. We made the convergent point of the beam overlap the curvature center of a concave mirror. The reflected beam from the concave mirror was used to readout the holograms. By this method, we suppressed the noise caused by superimposition and realized noise-free readout in holographic storage.

The measurements on the intensity of the diffracted beam of transmission gratings were done. The gratings with different center-to-center separation were illuminated by the light beams with different polarizations, the ratio between the intensities of P-polarization and S-polarization shows clearly the vector properties of grating.

Grating lenses are diffractive optical elements with gradually variant space and line, and are widely applied to various optical systems, such as harmonic wave separation and diagnosis of high power laser system, optical communication and spectral analysis. Because of its small feature size (just about several times of the illumination wavelength) and gradually variant space and line, the simulation results are not accurate when using the scalar diffractive theory. In this paper, the grating lenses are subdivided into smaller areas, and every sub-area is regarded as periodic microstructure because variance of adjacent period is very small. Then Fourier modal method is adopted to analyze their diffractive properties in sequence, and finally total diffractive efficiency of grating lenses can be easily obtained. Its physical concept is clear and concise, and computation cost is small. Through numerical simulation, diffractive efficiency of grating lens for beam sampling and harmonic separation in high power laser system is calculated. It indicates that the method presented in this paper is accurate and valid. In addition, fabrication errors effects on diffractive efficiency are also simulated in order to obtain the relationship between process errors and diffractive efficiency of grating lenses. It suggests that grating lenses not only can be easily realized in fabrication process, but also can meet practical demand in high power laser system. In experiment, a beam-sampling grating with diameter 100 mm was fabricated, and its experimental diffractive efficiency is consistent with result calculated by the method in this paper.

In this paper, a red-sensitive photopolymer based on multiple polymerizable monomers is developed for holographic applications. The detailed quantitative experiments on the reagent concentrations, the exposure, the thickness of the photosensitive layer, are conducted to determine an optimum recipe, and bright volume phase holograms with high diffraction efficiency are obtained in our experiments at the exposure level of 4mJ/cm². This photopolymer also has higher resolution and self-development capacity. This makes it very convenient and useful for the applications of both real-time and double exposure holographic interferometry, some preliminary experiments of holographic interferometry are demonstrated in this paper for the nondestructive testing and measurement of minor distortion and displacement.

It is presented in this paper an improved simulated annealing algorithm with the ability of increasing sampling resolution and generating grating pattern with smoothed borders to design two-dimensional (2-D) non-separable Damann grating. Numerical simulations are performed for the lateral fabrication error accompanied in the lithography procedure and the measured experimental results of the fabricated grating agree with the simulation.

The electromagnetic theory should be applied to determine the diffraction efficiency of structures whose minimum line width is comparable with wavelength or the grooves are too deep, where scalar theory is no longer useful. The coordinate transformation method (the C method) is a very efficient method for obtaining continuous surface-relief grating efficiency for both TE and TM polarization. The local linear grating model (LLGM) models 2-D circular diffractive lens with combination of a series of local linear gratings. We synthesized and analyzed circular diffractive lens with a continuous profile not as previous authors who always use multi-lever structures. The result is compared with that of scalar theory and analysis using LLGM and rigorous coupled-wave theory. This optimization can be used as a complement of the scalar design of diffractive lens.

Variable Line-Space gratings play an important role in focusing and aberration-reduced. They are widely used in spatial spectrum and synchrotron radiation facilities. However the design and fabrication methods of them are difficult. The problem is to be able to record holographically the expected grooves distribution. The geometric theory of aspheric wave-front recording optics is briefly described. We introduce the genetic algorithm to the parameters optimization of holographic variable line-space gratings. In order to obtain a steady set of recording parameters, we propose that the objective function of the genetic algorithm should consider the effect of the recording parameters errors. The integral expression of the objective function is also derived to improve the efficiency of calculation. Design example of holographic variable line-space plane gratings for a position sensor is given to demonstrate the capability of this method. The line-profiles of variable line-space plane gratings with different recording parameters are also compared in this paper.

Liquid crystalline compounds with a siloxane component in the tail were found to be effective in the formation of holographic gratings of polymer dispersed liquid crystal systems over a wide concentration range from 3wt% to 30wt%. The structure of the siloxane chain had a big effect on the performance of the gratings. Fine gratings with a diffractive efficiency of 40wt% could be formed with a liquid crystalline compound containing 3wt% disiloxane.

Color Separating Grating (CSG) is one of the important Diffractive Optical Elements (DOE) used in the final optical system of high power laser system. Its periodic step-phase structure can separate the third harmonic frequency from base- and second-harmonic waves in the far field. But the structure abbreviations of CSG, caused by the fabrication process, generate great modulations to the laser beam, which may lead to severe optical damages to CSG itself and the system. In this paper, a comprehensive error model is built, in which each structural parameter of CSG is expressed as a variable, and the structural parameter error induced by fabrication process is expressed as minute disturb of relative variable. With this error model, the near field diffraction pattern of CSG is calculated based on Fresnel diffractive theory. Through simulation and analysis, we obtain the amplitude modulation of different harmonic waves in near field, and also the relationship between the amplitude modulation and the fabrication error. The results show that beam modulations are mainly caused by the stair depth error and the slope error. This study provides a convenient way to estimate the possibility of optical damages induced by CSG.

A number of current and future optical and optoelectronic devices require the creation of structure in HfO₂ film. The reactive ion beam etching of HfO₂ film and photoresist mask in Ar/CHF₃ gas mixture was examined as a function of ion energy, discharge composition and ion beam incident angle. The details of etch rate have been interpreted in terms of mechanism of etching. The etch rate has shown a square root dependence on ion energy and variation versus incidence angle. The CHF₃- plasma produced some chemical enhancement in HfO₂ film etching. Compared with pure argon etching, better selectivity and higher fidelity pattern transfer were achieved with Ar/CHF₃ for HfO₂ film over photoresisit mask. The AFM scans of etched HfO₂ film by tapping mode showed good surface quality.

Synthetic aperture technique can be used to improve the reconstruction image resolution of digital hologram. In this paper, a synthetic aperture digital holographic method is proposed. In the method, the recording of synthetic aperture digital hologram is carried out by means of object movement in one direction, and the reconstruction is achieved by cross-correlation synthesis technique. Compared to the digital holography without synthetic aperture technique, only a one-dimension movable bracket is added in the experimental setup. The recorded object fixed on the movable bracket is placed in Mach-Zehnder interferometer and moved along horizontal direction. For the purpose of aperture synthesis reconstructing, four sub-digital holograms have been recorded by a CCD camera. While recording, superposition area of about half pixels of single digital hologram size should be assured between the adjacent holograms in order to ensure that the sub-digital holograms are synthesized accurately. The experimental result shows that every horizontal line of the reconstruction image is distinct in the synthetic aperture digital hologram, but the transverse is unidentifiable in the images reconstructed from the single digital holograms. It can be seen obviously that compared to sub-digital hologram the reconstruction image resolution of synthetic aperture digital hologram is improved.

In this paper, we demonstrate long-term readout in a photorefractive memory with a dynamic refreshment technique by mutual-pumped phase conjugate mirror (MPPCM). The dynamic refreshment means that a volatile hologram is sustained in parallel with its reconstruction by only all-optical process. A simple optical feedback circuit for hologram sustainment by MPPCM is added on to a photorefractive memory in our dynamic refreshment technique. By continuously rewriting with feedback of reconstructed image, long-term continuous readout of a volatile hologram can be realized. This technique with MPPCM also offers grayscale-to-binary conversion by the beam resonance and intensity thresholding of MPPCM that it cannot be built up where the intensity is lower than the threshold level. By adjusting the proper threshold value, therefore, a noise-reduced binary image can be retrieved without any external processing systems. Moreover, high quality output data can be obtained because phase distortion on the image can be automatically removed by optical phase conjugation. This technology is applicable to recording technique such as angular and phase-code multiplexing and allows long-term readout of multiple holograms by the appropriate refreshing schedules. We perform the experiment on long-term readout using barium titanate (BaTiO₃) crystals and demonstrate a recorded image is reconstructed over 1 hour with our technique whereas a reconstructed image fades away within 5 minutes with conventional readout technique.

The two-step holographic technique of fabricating blazed gratings has been successfully applied to common positive photoresist. Influence of three fabrication parameters in the second step on groove profile of blazed gratings was studied experimentally. The three fabrication parameters are exposure, incident angle of laser beam and development time. The exposure distribution on the cross-section of one groove stripe of grating was modeled. Results of experiment and modeling with various exposures reveal that the technique is effective only when the symmetrical contour lines of exposure in the first step fade out with increasing second exposure. With other parameters fixed, experiments were also carried out with the beam incident angle varying from 10° to 80° and with the development time varying from 1 s to 9 s. Blazed gratings with quasi-triangular are obtained when incident angle reaches 40° and when development time reaches 5 s. Scanning electron micrographs of the results are presented. Blazed gratings with observed blaze angles of 20° to 50° were obtained by changing the incident angle. Efficiencies of different diffraction orders for gratings with various incident angles are also given.

A method for displaying ordinary transmission holograms with white light and grating was investigated further. Based on the basic principle of this method, factors coming from the case of application and having influence on the image color and quality were analyzed systematically.

In the final optics assembly of ICF driver, Diffractive Optical Elements (DOEs) are applied to achieve some important functions. Due to the advantage of easy integration, DOEs that achieve different functions can be combined into one element, and thus the system structure and performance of ICF driver can be optimized. In this paper, we present a new means to fabricate color separation grating (CSG) and beam sampling grating (BSG) on two surfaces of one fused-silica substrate with two-surface exposure method. The mask for CSG can be fabricated with common optical method since the period of CSG is large; whereas the mask for BSG cannot be made with normal micro-fabrication system whose resolution cannot meet the requirement of fabrication precision of slowly changed BSG fringes (from 2μm to 4μm). Therefore, we use e-beam direct writing method to fabricate mask for BSG. The alignment of CSG and BSG is designed in accordance with the requirement of actual system. Thus the functions of harmonic wave separation and beam sampling are realized through one silica plate. The satisfying experimental results are illustrated.

In order to obtain a low polarization dependent loss (PDL) and a large attenuation range simultaneously, an optimal design and fabrication of a polymer-dispersed liquid crystal (PDLC) based variable optical attenuator (VOA) is presented. First, an optimal diameter of the liquid crystal droplets is determined by the anomalous diffraction approach (ADA). This optimal diameter gives maximal scattering and thus a large attenuation range is achieved with a relatively thin liquid crystal cell. Secondly, the fabrication of PDLC cell is carried out. The influence of the ultraviolet (UV) curing condition on the morphology of the LC droplets is investigated. For a given liquid crystal concentration, the optimal UV curing power is obtained after a series of statistically designed experiments. Finally, an optical configuration of the PDLC based VOA is presented. Measurements of the attenuation and the PDL are carried out with this configuration. The measured results show that the device has a typical attenuation range of 25dB. The corresponding PDL is nearly 1dB and the insertion loss is 1.8dB. The threshold voltage is 8Vrms and the saturation voltage is 40Vrms. From these measured results, one can see that the fabricated VOA based on PDLC is much more practical for optical communications as compared to the existing ones.

A new optical encryption technique based on computer-generated hologram (CGH) and fractional Fourier transform (FRT) is presented. And the algorithm of making asymmetry FRT CGH is provided in this paper. In this method, the fractional Fourier transform of the input image is performed by two one-dimensional FRT with different orders in the x and y directions in cascade. With Lohmann III detour phase encoding method and computer plotting program, the transformed image is encoded and fabricated into CGH on the computer. Then a piece of asymmetry fractional Fourier transform CGH (AFRTCGH) of original input image is obtained. In order to reconstruct the encoded image, a special fractional Fourier transform systems with two special cylinder lens’ are needed. Namely, only when the transform order in each direction is respectively matched with that of the asymmetry fractional Fourier transform CGH, can the encoded image be reconstructed exactly. Because of its particularity of image reconstruction, it is regarded as a new optical security system and can be used in anti-counterfeiting. When it is used to encrypt image or to anti-Counterfeit, anti-counterfeiting intensity can be improved greatly. So it has very high applying value.

Water-resisting red-sensitive photopolymer with simple reprocessing has high sensitivity, high diffraction efficiency (>80%) and large refractive index modulation. Sensitivity and resolution is increased by using compound spectral sensitization compound coinitiator and compound monomers. The polymerization of the monomer can be controlled, and so the holograms preserved in the natural environment for a long time do not disappear. The photopolymer holographic recording materials without hidden reaction have good physical and chemical stability. The result of research indicates that the holographic recording plates have better real-time character. The photochemical polymerization mechanism and the effects of the components on the photopolymerization rate are investigated, and other characteristics about this material are also analyzed. In addition, the photopolymer is harmless and pollution-free, and so the photopolymer has large practical value and prospects of wide applications.

A novel speckle averaging technique for DSPI static deformation measurement is proposed in this paper. This method combines the speckle averaging and phase-shifting technique. A speckle averaging mechanism is designed and fabricated. Its stability and repeatability is high, so it can meet the requirement of the DSPI static deformation measurement. Using this technique, the quality of result of DSPI static deformation measurement is improved greatly. The algorithm of speckle averaging is described in detail. The comparison of results of different speckle averaging times is presented in this paper.

The photorefractive BGO crystal shows rapid respond (second level) when applied by external electric field, but it has weak photorefractive effect. CeO₂ and CuO co-doped BGO (Bi₁₂GeO₂₀) crystal has been grown by Czochralski method for the first time. The diffraction efficiency and respond time of Ce:Cu:BGO and BGO crystals are determined with two-wave-coupling technology. The phase conjugate reflectivity and respond time are also determined in four-wave-fixing optical path. The results indicate that diffraction efficiency and phase conjugate reflectivity of Ce:Cu:BGO is 30% higher than those of non-doped BGO and the response time exhibits in second level with 6kv/cm² external electric field. The improvement mechanism of photorefractive effect of Ce:Cu:BGO crystal is investigated systematically.

In this paper, a blue-sensitive photopolymer holographic recording material was prepared. The visible-light sensitive photoinitiating system was composed of sensitizer, initiator, hydrogen-donor, monomer and binder. Compound sensitizing as a new method for improving exposure sensitivity of this material was proposed. Experiments results indicate that compound sensitizing significantly increased the exposure sensitivity from about 55mJ/cm² to 40 mJ/cm², while without any affection to the maximum obtainable diffraction efficiency. More than 85% of transmission grating diffraction efficiency can be attained as a very simple post process was performed. Mechanisms of polymerization and hologram formation were discussed. The holograms, with a good physical and chemical stability under ambient circumstance, have much potential in optical communication, such as filters and switches.

We report on diffraction performances of deep-etched transmission gratings in fused silica at the wavelength of 1.55μm. Profile parameters of the depth and line density are optimized to achieve the first order Bragg transmitted efficiency of more than 98% theoretically under TE- or TM-polarized incident lights. Spectra performance of a 630 lines/mm grating with the depth of 3.0μm in the C+L bands is presented in which the diffraction efficiency of each spectrum can be above 90%. By holography and inductive coupled plasma (ICP) etching, we have made a fused silica grating with the period of 610lines/mm and the depth of 0.73μm, the first order Bragg diffraction efficiency of which can reach 17% at the wavelength of 1.31 µm and 10% at 1.55 μm. Our results provide an important guideline for transmission gratings in fused silica as (de)multiplexers for dense wavelength division multiplexing (DWDM) application.

To collimate effectively the beam emitted from the stacked laser diode in which the lasing surfaces of the diode bars are not located in a plane, a new type of fast-axis collimator, refractive cylindrical microlens array with tunable focal lengths, is presented in this paper. Each lens of the array has the same diameter of 300μm but different focal lengths, ranged from 430μm to 540μm. By means of the mask moving lithography and replication technology, the microlens array was successfully fabricated. The measured fast-axis divergence of the stacked laser diode beam after the collimator was 25mrad, about half of the one (40mrad) for the microlens array with common focal lengths of 400μm.

Different ways of showing display holograms to students are introduced in this paper, including: (1) Showing display holograms to the class in the classroom. (2) Showing display holograms to the individual students. (3) Visiting display hologram exhibitions. (4) Making and showing hologram Jpeg/Mpeg movie clips on the screen. (5) Making and showing hologram Quicktime movie clips. (6)Making and showing movie clips for students to study basic holography principles. More than 10 movie clips are made for showing display hologram principles in classroom.

Photonic crystal template can be fabricated by holographic lithography in photoresist. A method for enhancing the quality of holographic photonic crystal template is mentioned in this paper. Because light energy is absorbed by photoresist while propagating through the material, the exposure decreases with the depth of the photoresist layer. In order to compensate for the light energy losing in exposure process, the recording plate is flipped to let the interference beams incident on the side of glass substrate instead of the surface of the material. During the development, the etching is proceeding quickly into the lower part of the material while the structure on the surface is maintained. Experimentally, face centered cubic lattice structures were fabricated in the AZ-4620 positive photoresist using an Ar⁺ laser with wavelength of 458 nm. Good 3D lattice structures have been obtained using this method. Theoretical analysis, computer simulation and experimental results obtained with the interference beams incident on different sides of the photoresist plate are presented in the paper.

All-optical interconnections are expected to play an important role in optical computing and neural network systems. Some schemes of the interconnection with a mutually pumped phase conjugate mirror (MPPCM) have been proposed. But it takes long time for reconfiguration of the wiring pattern because the competition among a lot of the index gratings induced by the incident beam and its scattered beams forms MPPCM gradually. In this report, we propose a new optical interconnection by using mutually pumped four-wave mixing (MP-FWM) which is composed of a MPPCM and a degenerate four-wave mixing (FWM). In this method, the two control beams induce the hologram that determines the wiring pattern of the signal beams in the FWM region. On the other hand, the signal beams are transferred to the phase conjugate beam of the one of the control beam through the FWM region by using MPPCM and then the signal beams are diffracted to the desired output channels by the hologram in the FWM region. This scheme can reduce the time to reconfigure the wiring pattern remarkably compared with the conventional interconnection using only MPPCM because the hologram can be reformed by the two control beams arbitrarily. It also can suppress the channel crosstalk that is often generated by the photorefractive fanning effect. This interconnection is effective method to solve the problems of the electrical wiring techniques such as the electro-magnetic interference and the thermal generation. We give the experimental result by using BaTiO₃ crystal and Ar⁺ laser, and investigate the optimum condition of the beams for high connection efficiency.

In this paper, we investigate photopolymer based holographic off-plane coupler experimentally. In our scheme, holograms are recorded inside the photopolymer slab waveguide by two-beam interference. The optical beams are vertically coupled into the waveguide through the recording position over the polymer substrate. The coupled optical beam propagates in the photopolymer slab waveguide. The beam profile radiated from the cut end of the waveguide and measured energy transfer efficiency are presented.

The basic starting point of the digital hologram’s image-forming system is to employ two-dimensional medium for expressing three-dimensional image or recovering three dimensional objects. By virtue of the computer coding technology, we reconstruct object’s reproduction image, and use red-sensitive photopolymer to make hologram. In this paper, we discuss two record devices, that is, the Charged Coupled Device and the digital camera. We mainly focus on two kinds of spatial light modulator, and choose one to project images. As for the holographic record material, we use a sort of self-made photopolymer, which is a contamination free record material. In the experiment, we have received certain fine results.

It is reported in this paper a method to fabricate three dimensional continuous micro-optical structures using half tone masks and proximity printing. The frequency modulation coded half tone masks are employed to obtain the predetermined exposure distribution. Several components like Cylinder microlens arrays, phase correctors are realized in photoresists.

This paper analyzes the reflection index modulation distribution and the corresponding spectrum characteristic of the holographic reflection gratings fabricated by Lippman light path under the condition of recording medium absorption being taken into account. The emphasis of discussion is placed on the relationship of secondary peak characteristic of the holographic reflection gratings, bandwidth and the distribution of refraction index modulation under this recording condition, calculating and simulating the distribution curve of refraction index modulation and the corresponding spectrum characteristic curve of diffraction gratings, and the comparison with the holograph gratings recorded by symmetrical light path. The result of calculation shows that there is obvious difference between the spectrum characteristic curve of Lippman holographic gating and that of symmetrical light path, and the secondary peak value of Lippman holographic gratings is lower than that of symmetric light path under the condition of the same reflection index modulation, while the medium of recording is thicker (thicker than 60μm) or the non-linear modulation of refraction index is relatively large, and the higher secondary peak of Lippman holographic gratings presents saw-like and non-degressive, whereas this phenomenon has never occurred in the holographic gratings diffraction recorded by the symmetrical path. This result obtained by calculation and simulation is consistent with experimental result.

A bubble in water is an example of a scatter for which the refractive index of the core (gas) is less than that of the surroundings. So bubbles in water exhibit scattering phenomena which differs significantly from those for drops in air or solid particles in water. The scattering of bubbles in water as a means to detective the size of bubble has been investigated in many ways such as Mie theory and Davis’s geometric-optics theory. In this paper, a new physics-optics method was applied to manifest the scattering properties of a spherical bubble in water. The angular distribution of intensity of light scattered from a collimated beam that is incident upon a spherical air bubble in water is determined for any bubble with radius greater than a few wavelengths of the incident light. One external reflection, four internal reflections and four refractions are considered. The intensity of scattering light is tabulated and plotted as a function of the observing angle, the effects of the bubble’s radius, the electric field’s polarization of the incidence light and the wavelength of the incidence light on the scattering intensity distribution are also discussed.

In this paper, performance of holographic storage based on doubly doped Fe:Mn:LiNbO₃ crystal with 0.03 wt% Fe₂O₃ and 0.1 wt% MnO dopants which was great contrastive against previous investigations was studied theoretically and experimentally. We established the coupling differential equations using the band-transport model. Using practical experiment parameters, we numerically calculated and explained the time-dynamic developing process of the holographic storage, and analyzed how the oxidation-reduction degree of the crystal affects the space charge field within the crystal. Only the oxidative crystals can accomplish nonvolatile holographic storage but not the reductive crystal. For the oxidative crystal, its remaining magnitude of the space charge field increases with the increase of oxidative degree. Further more we measured the diffraction efficiencies of four specimens with different degree of oxidation-reduction and realized holographic multiplying and holographic fixing in the oxidation crystal successfully. Based on the experiments, we also calculated both the dynamic range parameter M/# of the oxidized doubly doped Fe:Mn:LiNbO₃ crystal and the recording sensitivity of various crystals. The experimental results coincided with the theoretical analysis very well. Diffraction efficiency of fixing grating increased with oxidation, photorefractive sensitivity decreases with oxidation, higher the concentration of doped manganese and oxidation, the larger the effective dynamic range of holographic storage system is, where holograms can be stored permanently.

Antireflection coatings are studied for increasing the transmitted efficiency of diffractive optical elements. Numerical simulations of different beam-splitters show that noticeable increase in efficiency can be reached with a particular optimized structure.

The noise characteristics and gain saturation of bidirectionally pumped Raman fiber amplifier (RFA) are investigated in detail. The results show that the noise characteristics of bidirectionally pumped RFA are intermediate between that of the co- and counter-pumped RFA, and can be improved by the reasonable increment of co-gain. The saturation power is decreased and the gain saturation phenomenon is deepened with the increment of the ratio of the co-gain to the counter gain.

Bragg grating has lots of use in many optical field. Especially, in dense wavelength division multiplexing system and optical filters, and so on. Holographic Bragg grating with 1800 line/mm is fabricated in this experiment. Performances of holographic Bragg gratings are measured in our lab. Results show that this holographic Bragg grating can resolve 0.26nm fine line spectrum. Diffraction efficiency of Bragg grating can get 76% in 1.55 μm wavelength. Results also show that this kind of holographic Bragg grating may use in DWDM device and can produce fine narrow width spectra.

We made the complex hologram of a three-dimensional image using the modified triangular interferometer, and presented and analyzed the three-dimensional images numerically reconstructed from it.

Acousto-optic tunable filter (AOTF) is one of important optical switch components in optical networks. The possibility of tellurium dioxide acousto-optic tunable filter (TeO₂ AOTF) as an optical add/drop multiplexer (OADM) is studied on the basis of the theory of the anomalous acousto-optic Bragg diffraction and the design principle of non-collinear AOTF. Its main performances and structure are analyzed and discussed, and the significance of incident angles and interaction lengths for its performances is presented. The model for optimization design is built under some limitation and the transducer areas is adopted as a regulator for performance, the designed example of the TeO₂ AOTF for WDM systems is given by the optimized method.

In this paper, a kinoform with the characters of two-channel was fabricated by adding quadratic phase factors into Fourier frequency spectrum of object. We adopt the Gerchberg-Saxton (G-S) iterative algorithm and iterate many times between the space field and frequency spectrum field, while keeping the amplitude of frequency spectrum approximately to constant. The phase of the spectrum is quantified. An eight-phase-level kinoform of two-channel is fabricated by using the micro-optical technique. The two separate reconstruction images are clear and the efficiency of the diffraction is 58.5%.

We have experimentally observed diffractive effects of a supercontinuum laser pulse with a spectral range from 600 to 950 nm. The spectral tilt has been demonstrated, which is in accordance with our numerical results.

A novel wavelength-time differential code division multiple access system is proposed for multirate transmission. The system model is given and analyzed. Differential detection can be adopted by assigning two orthogonal codes for one user and using these two codes to encode “1” and “0” with different period, respectively. When one-branch and zero-branch are balanced perfectly, the system can reduce the noise of background, thermal, dark current, and multiple access inference. Moreover, by varying the ratio of number of bit ”1” and bit “0” in data steaming, the multirate data stream transmission is achieved.

OCDMA allows multiple users to share a common optical channel simultaneously and asynchronously, and thus has many advantages, such as great system capacity, efficient bandwidth utilization, asynchronous access, secure communication, and so on. Many studies on OCDMA techniques have been made in recent years. In direct-sequence (DS) incoherent OCDMA systems, each user is assigned a unique signature sequence (1’s and 0’s) for spreading and identification purposes. Through the use of encoding process, the user signal is spread in the frequency domain so that each user occupies the entire bandwidth available at all times. This results in a total bandwidth utilization. The optical medium is superbly suited to spread spectrum multiple access communications due to its extremely large bandwidth, however the spectral efficiency of OCDMA system is an important factor. This paper analyses the spectrum efficiency of incoherent OCDMA systems, emphatically discusses several kinds of codes, compares and evaluates their performances.

The results of theoretical investigation of recording superimposed holographic gratings of transmitted type in optical absorbent photopolymeric materials are presented in the report. We consider the case of serial record of superimposed holographic gratings with angle multiplexing. The influence of photopolymer material parameters on diffraction effectiveness of superimposed holographic gratings is investigated in the work. It shows that the change of optical absorbent photopolymeric material during record may strongly change integrated diffraction characteristics or the recorded holographic gratings.

Based on the focus principle of the zone plate and the encoding method of the computer-generated hologram, a zone plate applied in OCT to increase the focal depth is proposed. The phase distribution of this kind of zone plate is constructed by superimposing a shifted elliptical phase to the phase function of a common sine zone plate, which will confine the spot size of the focused beam within a particular range along axis and thus extend the focal depth. The numerical simulation shows that the focal segment of the zone plate meet the requirement of the commonly used OCT imaging system in the two aspects of focal depth and transverse resolution. Because the zone plate has many advantages such as flexible focal length and depth design, simple structure for fabrication, low cost and convenient micromation and integration, it is a potential long focal depth component for optical coherence tomography.

Fabricating holographic apodized gratings is often impeded by nonlinear property of materials, which makes the resultant profile out of expectation. In this paper, the new scheme to fabricate Gaussian apodized grating is proposed. Instead of fixed Gaussian recording beams, recording beam profiles that can compensate the nonlinear sensitivity of the material at low recording intensities are created by a gray level spatial light modulator (SLM). DuPont’s HRF-150-38 photopolymer is chosen because of its stability and ease to use. As the first result of the experiment, a Gaussian grating of 2.7±0.02mm standard deviation is recorded at 0.3mW/cm² recording intensity after exposure of 300 seconds.

We reported the previous research of spectrum imaging with a double-grating imaging system in 2001. In this paper, we will investigate the energy of the image obtained using the same imaging method. A mercury-vapor lamp was used as the light source to measure the light energy of the image at different positions for four grating combinations. The experimental results were analyzed systematically. The factors affecting the brightness of the image were also discussed in this paper.

A facilitated fiber Bragg grating detection system for detecting temperature is presented. The scheme uses a processing fiber Bragg grating that is stuck on a cantilever beam and is identical to one used as a sensor to demodulate the temperature signal. A step motor that is controlled by PLC (Programmable Logic Controller) stretches the cantilever beam periodically, and the system of two gratings produces a carrier at this frequency with its phase modulated by the temperature signal applied to the sensing grating. The temperature signal, which is demodulated by this system, is transmitted to PC then processed and displayed in PC. This system’s configuration is simple, sensitivity is high, and cost is low.

In this paper, the influence of the pulse exposures repetition frequencies on volume holograms recording in photopolymer films is studied. Using a pulsed diode-pumped YAG laser (532-nm wavelength) as recording source, volume holograms are recorded with the same pulse energy fluence (0.1mJ/cm² per pulse) but different pulse exposures repetition frequencies. The diffraction efficiency and light scattering are real-time measured as the holographic grating is formed. Experimental results show that the maximum diffraction efficiency and refractive index modulation can be obtained at an optimal repetition frequency. And an upper limit for total exposure energy and an optimal pulse repetition frequency are necessary to keep low scattering noise.

A new experiment method for recording the hologram by CCD with less distortion and reconstructing the original image with high quality is described in this paper. The feature of this developed method is that conjugate and zero-order image can be eliminated simultaneously by setting their spectrum zero in spatial domain. The results have demonstrated that it is an efficient method of image acquisition and the reconstruction with high quality in digital holography.

Projection moire topography measurement is a useful method of non-contacting 3-D shape measurement in the engineering fields. Presently in projection moire topography measurement, an image of the long period grating lighted by a white light source is projected onto the object by projection lens so that the binary shadow fringes are obtained by viewing it through a second grating in front of the camera. The fringes form the binary moire topography containing the information of surface profile. The 3-D shape of the object is rebuilt by analyzing the moire topography. Due to using a long grating period and error of the projection lens the resolution and precision is lower. And because the binary fringes in a frame of topography image contained fewer the altitude information of the object, the distortion existed in the 3-D shape rebuilt. For all above problems, a novel method of multi-spectral projection moire topography measurement is proposed in this paper. The method uses the virtual grating with alterable period and polychromatic light source. The color fringes are generated by polychromatic light interferometry and projected onto the objection. The color fringes are modulated by surface profile of the object. The image of the curved color fringes is seen on the color CCD camera through the receiving optical system. In the receiving optical system the color fringes are selected according to the colorimetric principle. Thus the different wavelength color fringes form the color multi-channel. The image received by the color CCD camera is compound multi-channel color moire topography. The compound color moire topography image is separated into single color channel topographies by image processing. The different color channels provide more altitude information of the object than the binary moire topography. The 3-D altitude information that rebuilds the 3-D shape of the object finally is obtained by fusion of multi-channel topography. In the paper the principle of the method is proposed. And the effect on selecting grating period for the color interferometry fringes and the wavelength interval is discussed. The result of experimentation proves that the resolution of the projection moire topography reconstruction was effectually improved.