A polarizing, ytterbium-doped double clad fiber is demonstrated. Over 100 W of linearly polarized output power with a polarization extinction ratio of 17 dB is achieved from an all-fiber geometry.

This paper reports a new approach of applying erbium-doped fiber to an S-band optical amplifier and comparing it with a gain-shifted thulium-doped fluoride fiber amplifier. S-band erbium-doped fiber amplifiers for WDM transmission systems have achieved gains of over 25 dB in wavelengths from 1489 to 1519 nm through the use of silica-based EDFs and ASE suppressing filters. We discuss the feasibility of introducing S-band EDFAs to improve the power conversion efficiencies and gain flatness.

This paper reports on the preparation and the characteristics of Er-doped muliticomponent bismuthate channel waveguide. Dependence of emission lifetime of Er³⁺ ions on concentration of Er³⁺ ions is investigated. The concentration of Er³⁺ in the core film where concentration quenching effect starts is one order of magnitude higher than that of silicate materials. We show that the lower the hydroxyl ion content is, the longer the emission lifetime becomes and the emission lifetime of dehydrated core is the same as that of the fiber perform, namely the same quantum efficiency. The loss of the fabricated channel waveguide measured by cut-back method is 0.15 dB/cm at 1310 nm. Net gain of 8 dB is obtained at 1530 nm by using a 6-cm long waveguide pumped at 980 nm.

Wavelength of 2000 nm single mode microsphere laser from highly thulium doped tellurite glass microsphere was demonstrated by means of fiber taper coupling. Laser wavelength was red shift from the emission peak of thulium ions at 1800 nm.

Novel multi-wavelength switching filters based on cascaded long-period fiber grating (LPG) and polarization-maintaining fiber (PMF) in a Sagnac loop configuration are proposed and experimentally demonstrated. While the multi-channel spectrum of PMF Sagnac loop filter is controlled by the polarization state in the loop, the polarization-independence of the LPG filter is used to drop one channel. The polarization-independence of the cascaded LPG filter is also used for the fixed periodic loss spectrum to drop multiple channels in the loop. Although the polarization state of the optical wave filter is switched by the electro-optic modulator in the loop, the device is independent of the polarization state of the input light due to the bi-directional polarization compensation of the Sagnac loop interferometer. This device can be used to achieve all-channel gating and odd/even-channel switching with fine channel selectivity and high speed response.

With the introduction of wavelength division multiplexing and dense wavelength division multiplexing, equipment manufactures have sought to reduce design tradeoffs and costs while maintaining or increasing their product performance. With the need to reduce if not eliminate optical losses and create the all light path from source to destination, equipment manufactures are addressing the concerns of component manufactures to provide increased performance to support configurable designs for 100, 50, and eventually 12.5GHz. One of the most reliable, robust, and high performance devices is the low polarization dependent loss (LPDL) diffraction grating used to disperse wavelengths for channel blocking, add/drop functionality and real time light path reconfigurations. The networks today have a variety of factors which contribute to the optical loss budget and impact system design cost, facility requirements, maintenance or replacement costs. These factors include first and second order polarization mode dispersion (PMD), polarization dependent loss (PDL), wavelength dependent losses, and chromatic dispersion (CD). Network designers and equipment manufactures have to consider each component capability and its impact to the systems bit error rate (BER). In order to gain an understanding of the advantages of components with low polarization dependency, we will summarize the effects that interplay with these types of components.

Silicon oxynitride (SiO_xNy) grown by plasma enhanced chemical vapor deposition (PECVD) is well-suited for the realized application of high contrast waveguides for the range of the refractive index can be largely tuned (1.45-2.0). SiO_xN_y AWG device with 3% refractive index difference (Δ) and the transmission spectrum of AWG's device indicated the insertion loss, crosstalk and side-lobe were lower than -3 dB, -15 dB and -40 dB, respectively, by 3D beam propagation method were investigated in this study. The chip size of the whole device is smaller than 4 cm x 1.5 cm, and the highest coupling loss of the rib waveguide for single mode fiber was about -1.6 dB. Based on the simulation results, the device can be really fabricated by thin-film deposition, photo-lithography and dry-etching processes. Microstructural evolution analysis revealed over-supplied silicon atoms would form silicon nano-crystallized structure in the amorphous optical films for lower N₂O/(N₂+NH₃) ratio, and resulted in higher refractive index and extinction coefficient. From the scanning electron microscopy (SEM) features of rib-type silicon oxynitride waveguide, we found the profile, and the roughness of side- and top-walls of waveguide reached to the manufacturing criteria of AWG device. We had successfully fabricated an AWG device with 8 channels and 1.6nm channel spacing, and the coupling loss and propagation loss were about -2.24 dB and -0.15 dB/cm, respectively. While, the AWG device performances need further improvements by modified design, uniform thin film deposition, and accurate dry-etching processes.

In this work, we have studied the concentration quenching of the ³H₄→³F₄ emission of Tm³⁺ doped lead-niobium-germanate glasses (GeO₂-PbO-Nb₂O₅) for different Tm³⁺ concentrations (0.1, 0.2, 0.5, 1, 2, and 3 wt%). The emission spectra obtained under 798 nm excitation reveal the existence of energy transfer via cross-relaxation among Tm³⁺. As a result, the intensity of the infrared ³H₄→³F₄ emission at 1474 nm decreases in relation to that of the 1820 nm emission as concentration increases. The non-exponential character of the decays from the ³H₄ level with increasing concentration, together with the dependence of the effective decay rates on Tm³⁺ concentration, indicate the presence of a dipole-dipole quenching process in the framework of a diffusion-limited regime.

To investigate the effect of divalent cations, we melted a set of sodium silicate baseline glasses with different concentrations of Ca²⁺, Mg²⁺, and Zn²⁺. We doped each of these basic glass matrices with several different amounts of Er³⁺ cations. These samples have been characterized in terms of absorption spectra, luminescence spectra, and experimental lifetime of the erbium metastable state. We also fabricated planar waveguides using Ag⁺/Na⁺ ion-exchange process. Characteristic parameters of the waveguides such as the number of modes, the refractive index change, the depth of the diffused region, and the propagation loses were measured. The mutual replacements of the divalent cations influenced the electron donor power (basicity) of oxygen atoms coordinating metal ions in glass. Measured optical spectra, lifetime values, and waveguiding parameters reflected the changes in glass basicity. To quantify the individual effects of Ca²⁺, Mg²⁺, and Zn²⁺, we calculated composition-property models based on polynomial functions with multiple variables. Correlation coefficients R² varied from 0.991 to 1.000 indicating good linear correlations between the parameters and composition. The evaluation of glass component effects on the studied parameters enabled us quantify the chemical influence of the divalent cations. We discussed this influence using the optical basicity theory that predicts the variations of the electron donor power of oxygen atoms with glass composition. The knowledge of component effects is very useful for the effective formulation of new glass compositions. New Er glasses containing Zn²⁺ and/ or Mg²⁺ as divalent cations are promising materials for optical waveguide amplifiers.

An attempt has been conducted to develop multicomponent transparent glass-ceramics which have athermal property better than silica glass. Transparent Li₂O-Al₂O₃-SiO₂ (LAS) glass-ceramics with small thermal expansion coefficient was chosen as a candidate. Athermal property of the glass-ceramics was improved by the independent control of temperature coefficients of electronic polarizability and thermal expansion coefficient, both of which govern the temperature coefficient of optical path length. It was found that temperature coefficient of electronic polarizability and thermal expansion coefficient of the LAS glass-ceramics were controllable by the additives and crystallization conditions. The doping of B₂O₃ and the crystallization under a hydrostatic pressure of 196 MPa were very effective to reduce temperature coefficient of electronic polarizability without a remarkable increase in thermal expansion coefficient. It was deduced that the reduction in temperature coefficient of electronic polarizability by the crystallization under 196 MPa resulted from the inhibition of the precipitation of beta-spodumene solid solution. The relative temperature coefficients of optical path length of B2O3-doped glass-ceramic crystallized under 196 MPa was 11.7 x 10^-6/°C, which was slightly larger than that of silica glass. Nevertheless, the thermal expansion coefficient of this glass-ceramic was smaller than that of silica glass.

Several modified silicate glass samples activated with erbium ions at two different doping rates, namely 0.2 and 0.5 mol%, exhibit at room temperature a fine-structured emission band around 1.5 mm. The decay of luminescence from the Er^{3+ 4}I_13/2 metastable level is found to evolve according to a single-exponential law and a lifetime as long as 14.2 ms is measured from the glass with the lower erbium concentration. An estimation of the corresponding radiative lifetime, τ_rad, is achieved on the basis of various theoretical models. Internal gain curves resulting from absorption and stimulated emission cross sections are also shown. A 75% quantum efficiency is deduced for the less Er³⁺ concentrated glass, which is nearly the highest one obtained from silica based doped-glasses.

We introduce a new fabricating technique that forms a light emitting layer on silicon wafer. This emitting layer could emit light at 1530nm. We mix the Er₂O₃ nanoparticles with spin-on glass, then deposit this mixed solution onto silicon wafer. It emits 1530nm light because Er₂O₃ nanoparticles release Er³⁺ into glass at high temperature. The manufacturing process is very simple and low cost. We also add P₂O₅, Si, Al, and Ag nanoparticles in order to modify the physical characteristics and light emission efficiency.

Laser-induced micro-fabrication has many advantages such as maskless, single-step and very fast processing compared with current techniques such as photolithography and reactive ion etching. Laser-induced crystallization is now a big challenge in glass materials. A new technique for the writing of crystal dots and lines in glass, called "samarium (rare-earth) atom heat processing", has been developed, and the writing of several crystal lines such as b-BaB₂O₄ (b-BBO), Sm_xBi_1-xBO₃, Sm₂(MoO₄)₃, and KSm(PO₃)₄ showing second harmonic generations and ferroelectricities has been succeeded. It has been also demonstrated that two-dimensional crystal curved lines with bending angles of 0~90o or with sine-curve shapes can be written using the samarium atom heat processing. The features of this new technique and the quality of crystal lines have been clarified.

Subwavelength-diameter silica wires fabricated using a taper-drawing approach exhibit excellent diameter uniformity and atomic-level smoothness, making them suitable for low-loss optical wave guiding from the UV to the near-infrared. Such air-clad silica wires can be used as single-mode waveguides; depending on wavelength and wire diameter, they either tightly confine the optical fields or leave a certain amount of guided energy outside the wire in the form of evanescent waves. Using these wire waveguides as building blocks we assembled microscale optical components such as linear waveguides, waveguide bends and branch couplers on a low-index, non-dissipative silica aerogel substrate. These components are much smaller than comparable existing devices and have low optical loss, indicating that the wire-assembly technique presented here has great potential for developing microphotonics devices for future applications in a variety of fields such as optical communication, optical sensing and high-density optical integration.

We find that the evolution of an optical polarization along a twisted optical fiber may be spatially synchronized with polarization-selective light scattering. We demonstrate experimentally that linearly polarized light initially oriented along the fast axis of an adiabatically twisted single-mode, polarization-maintaining optical fiber is converted into elliptically and then into circularly polarized light with the same handedness as the chiral structure. As the state of polarization is changing along the length of the fiber, the light is scattered out of the fiber core. By choosing an appropriate twist acceleration profile in custom-made, rectangular-core polarization maintaining fibers, scattering and conversion may be synchronized, allowing the orthogonal polarization to freely propagate through the fiber. When the portion of the fiber with accelerated twist is combined with another fiber segment with decelerated twist, the fiber becomes a broadband, low-insertion-loss, in-fiber, linear polarizer. In this polarizer, the passing component of the incident light oriented along the slow axis, is converted to circularly polarized light of the opposite handedness, and then converted back to linearly polarized light oriented along the same slow axis. While the polarization evolution may be calculated using 1D model of light propagation through a birefringent medium, the calculation of light scattering requires a full 3D calculation.

We present here the design, fabrication and first measurements of integrated Bragg grating apodized filters, operating at a free-space wavelength of about 1550 nm, based on InP material line ridge waveguides. Their apodized transmission spectra are obtained by the mean of sampled grating structures. The fabrication process by means of electron beam lithography will be described. It has been used to realize the sampled gratings which are spatially localized on the wafer. The transmission spectrum of the filters is measured. The transmission dip is almost -30 dB over almost 0.25 nm which is in a good agreement with theoretical calculations. The suppression is better than 20dB outside a bandwidth of almost 1nm, whereas a uniform grating with the same dimensions only presents almost 10dB suppression outside the same bandwidth.

Bismuth based erbium doped fiber and highly nonlinear fiber exhibit inherent features which cannot be realized with silica based fibers. Extend L-band amplification, high gain C+L band amplification for coarse WDM and short pulse amplification can be realized using bismuth based EDF. On the other hand, step-index type fiber using bismuth based glass whose refractive index of 2.22 at 1.55μm is fabricated. This fiber exhibits high nonlinearity (γ=1360 W^-1km^-1) because of the high nonlinearity of the glass material and the small effective core area.

Spectroscopic properties of Ag/Er co-doped thin plates of silicate and phosphate glass were investigated with the aim of assessing the effective role of silver as a sensitizer for erbium. Additive heat treatments in air at different temperatures were performed on both a silver-exchanged and a silver-free plate in order to promote the formation of silver nanoparticles in the former and to refer to the later in the spectroscopic characterization. Absorption as well as photoluminescence measurements in the region of the ⁴I_13/2 -> ⁴I_15/2 transition of the Er³⁺ ion were performed; excitation wavelengths in the range from 360 to 750 nm were used. For the silicate glasses enhancement of the Er³⁺ luminescence at 1.53 mm was observed when the excitation wavelength was in the blue region. This spectral range typically coincides with the excitation energy of the surface plasmon resonance of nanometer-sized spherical silver particles.

A class of Nd-doped mix vanadate crystals Nd:Y_xGd_1-xVO₄ showed high potential in tailoring laser parameters for various applications with different Y and Gd composition ratios. Important thermal and thermo-optical properties, such as thermal conductivity and the temperature dependence of the index of refraction, were measured in these crystals along a-axis and c-axis. Results will be compared to well-known Nd:YAG, Nd:YVO₄, and Nd:GdVO₄ crystals.

A self-calibrating fluorescence spectroscopy technique was applied to study cross-relaxation ³H₄, ³H₆ → ³F₄, ³F₄, and energy migration ³H₄, ³H₆ → ³F₄, ³F₄, of the Tm³⁺ Ions doped in the tellurite glass. These glasses are investigated for their use in realization of 2 micron fiber lasers. Micro and macro-parameters of the energy transfer and migration were calculated by the means of the model of phonon-assistant multi-polar interaction and hoping mode. Steady rate equation analysis was used to fit the experimental fluorescence ratio of samples with different concentrations. We found that high-order (dipole-quadrupole) interaction was the dominant mechanism in the energy transfer of Thulium ions.

Emissions properties of glasses in the PbO-Ga₂O₃-Bi₂O₃ system doped with a variety of different rare-earth ions were reviewed with particular attention on the applications towards the amplification of the optical signals in the fiber-optic communication systems and for mid-infrared lasers. Due to the low vibrational phonon energy of the glasses, it was possible to realize the efficient emissions for the O-band and S-band amplification by doping Pr³⁺, Dy³⁺ or Tm³⁺. Amplification at these communication bands has not been possible when conventional oxide glasses were used as host materials. Network structure of the glass was made of mixture of GaO₄ tetrahedra and PbO₃/PbO₄ polyhedra as a backbone. They are connected through bridging oxygens and a portion of these oxygen atoms are connected to three cations instead of two. Pb²⁺ ions also act as charge compensators as evidenced from the large amount of non-bridging oxygens in the glass network. Bi₂O₃ form BiO₆ octahedra.

We propose an optical circulator formed of a magneto-optical cavity in a 2D photonic crystal. With spatially engineered magnetic domain structures, the cavity can be designed to support a pair of counter-rotating states at different frequencies. By coupling the cavity to three waveguides, and by a proper matching of the frequency split of the cavity modes with the coupling strength between the cavity and the waveguide, ideal three-port circulators with complete isolation and transmission can be created. We present a guideline for domain design needed to maximize the modal coupling and operational bandwidth for any given magneto-optical constant.

We investigated a novel possibility to attain all-optical logical gates. The host of the device was a thin-film semiconductor (CdS, GaAs, InP) on glass produced by various methods (pulsed-laser deposition and metal organic chemical vapor deposition). In the thin-film two visible laser beams, the primary and secondary ray, were crossed in the same spot. In this way, the secondary beam caused a transmission decrease in the primary beam. Laser crossing is an extremely undemanding concept based on electronic absorption alterations. Apparently, every semiconductor can be used for laser crossed all-optical logics and, in contrary to other semiconductor based concepts, laser crossing does not demand specific materials, material qualities or nonlinear features. The unmatched overall simplicity and possible THz operations recommend laser crossing for the realization of all-optical digital devices.

Recently, we reported a fast and simple iterative inverse Fourier transform algorithm that allows for the first time to determine the second-order optical nonlinearity profile of thin films uniquely from a classical Maker fringe measurement. In this work, we have applied this novel technique to study the quantitative effects of the poling time and poling field on the second-order nonlinearity profile of thermally poled silica (Infrasil) samples. This study has enabled us to optimize the poling conditions and produce a record peak nonlinear coefficient d33 of 1.35 pm/V (poling at 9.6 MV/m and 280 °C for 15 minutes). This coefficient is 70% larger than typical values reported for conventional poling conditions (~5 MV/m for 15 minutes). This investigation also yielded values for a number of interesting poling parameters, in particular the diffusion depth of the positive species injected into the sample during poling as a function of poling conditions. These results are important for understanding the physics of the induced nonlinearity and for optimizing future optical devices in poled silica.

Tapered high-brightness diode lasers are finding use in a variety of applications today. An increased brightness makes tapered lasers especially attractive for fiber applications, even for telecom applications like pumping of Er-doped fiber amplifiers or Raman amplifiers. In addition the use of tapered lasers in external resonator configurations is common practice for several applications, such as frequency doubling, which necessitate diffraction-limited tunable narrow linewidths together with high output powers. However, two disadvantages of the tapered laser concept are the reduced output power provoked by their additional resonator losses and the astigmatism. In case of high-brightness diode lasers it is important to discuss the methods needed for an advanced output power also from the beam quality point of view. The control of astigmatism is essential for designing micro-optics for laser modules. We have realized high-efficiency ridge-waveguided tapered diode lasers. These low modal gain, single quantum well InGaAs/AlGaAs devices emitting at 980 nm were grown by molecular beam epitaxy. The influence of the thermal resistance and of the tapered section length on output power as well as on beam quality has been investigated. The high-efficiency tapered diode lasers show promising output powers of more than 5 W and a nearly diffraction limited behav-iour up to 4 W. Used in an external-cavity configuration these tunable diode lasers show output powers of more than 3 W. The beam-quality parameter remains well below M² < 1.5 for output powers up to 2 W.

With the continuous advent of new multimedia technologies, the local network bandwidth is getting closer and closer to limits set by electronic switching constraints. All-optical networks have long been demonstrated in the laboratory and rely on nonlinear switching devices such as Michelson Interferometers (MIs) for all-optical routing and all-optical digital processing. Hybrid integrated MIs allow for a greater electro-optical integration and thus easier packaging. It was recently published that multi-contact optical amplifiers provide a greater ease of use due to their greater flexibility in injecting current into the device. We have therefore investigated the optimisation of twin-contact SOAs for use in one arm of a Michelson device in order to provide the highest possible optically induced phase shift sine qua non for interferometry. The SOA section length as well as the corresponding injection currents were optimised and it was found that non-symmetrical sections (i.e. of different lengths and injection currents) produces best results with phase shifts up to 8.6 radians for 541μm (333μm + 208μm) long devices. This is explained by the non-symmetrical gains saturation effects created by the co-propagating pump and probe signal when passing through the various SOA sections. Multi-contact SOAs are hoped to provide a new ways of designing hybrid integrated interferometric devices by allowing greater control over the optical amplification process within the device.

Dual-wavelength semiconductor laser with wavelength separation as large as 203 nm is reported. With the short-wavelength mode located in 1345.4 nm and the long-wavelength mode in 1548.6 nm, the operation region of the laser system covers both the medium-wave band (1300 nm region) and long-wave band (1500 nm region) in optical communication. Random selection of oscillating wavelength position between 1345.4 nm and 1548.6 nm is also possible with fixed wavelength separation. This broadband laser system provides an opportunity for all-optical switching between the medium-wave band and long-wave band in optical communication.

High power and good beam quality are desired for semiconductor lasers in many applications. We propose a new type of broad area laser diodes that is capable of emitting good beam quality, high power and broadband tuning. The new type of laser diodes is fabricated with a broad-area waveguide that is oriented at an angle from the facet normal. This device does not require the DFB structure, so the fabrication is much simpler. The L-I curves, spectra, near-field patterns and far-field patterns of the angled broad-area waveguide laser diode are measured. The direction of the far field pattern along the facet normal for the device operated above the threshold current indicates that the light path is not along the waveguide direction. As the laser diode is inserted in a grating-loaded external cavity, it is tunable from 1280nm to 1315nm with output power up to 1.4 watt at 8Amp. The beam quality is good and the near field has negligible filamentation.

The work is devoted to luminescent properties of trivalent lanthanide complexes dispersed in thermoplastic host matrices. Polyethylene-based film and polypropylene-based rod both doped with these complexes were manufactured using an extrusion technique. Two kinds of dopants were used: Eu(III)-thenoyltrifluoroacetone-1,10-phenanthroline complex (Eu(III)) and Eu(III)-La(III)-1,10-phenanthroline complex (Eu(III)-La(III)). Comparison was made between these samples regarding absorption, excitation, emission and a lifetime of luminescence. Dependence of emission intensity on the excitation energy was determined. Emission spectra of the films were studied at room and helium temperatures. Optical properties of Eu(III) samples are different from Eu(III)-La(III) samples. Significant difference in spectra of these two types of samples may be attributed to the La(III) action.

Tellurite glasses optical fibers became promising for optical amplifiers due to its high rare earth ions solubility and very large amplification bandwidth. Among several tellurite glasses the TeO₂-WO₃-Na₂O-Nb₂O₅ system show one of the largest bandwidth. Our previous characterization of lifetime using the omega2, omega4, omega6, Judd-Ofelt parameters indicate a quantum efficiency maximum for 7500ppm Er³⁺ concentration. Therefore we decided to produce jointed Er³⁺ and Tm³⁺ single mode optical fibers with this glass system keeping the 7500ppm Er³⁺ concentration and varying the Tm³⁺ concentration from 2500ppm to 15000ppm. This single mode fiber was pumped by 120mW of the semiconductor laser at 790nm and we observed a flat ASE bandwidth from 1400 to 1570nm for the 5000ppm Tm³⁺ concentration.

Tellurite glasses optical fibers became promising for optical amplifiers due to its high rare earth ions solubility. One of the most important parameter for optical amplification is the lifetime of the excited states, which strongly depends on the crystal field around the ions. That crystal field changes dramatically with the host glass and with rare earth concentration. Excited state lifetime studies have been performed on Er³⁺-doped-TeO₂-WO₃-Na₂O-Nb₂O₅ glass system. Therefore, we decided to study the Er³⁺ excited states lifetimes and compared with the Judd-Ofelt theory predictions. We measured only the ⁴I_13/2 to ⁴I_15/2 transitions lifetimes. The other transitions lifetimes can be inferred by knowing the Ω₂, Ω₄, Ω₆ Judd-Ofelt parameters. These parameters were calculated with the electric-magnetic dipole transition oscillator strength for the desired excited levels and ground state obtained from the optical absorption spectra. After performing this calculation we estimated that maximum quantum efficiency (η), measured/calculated lifetimes ratio, would be achieved at 7500ppm (%wt) Er³⁺ content.

A two dimensional acousto-optic cell array (AOCA) to be used as an optical MUX/DEMUX in DWDM systems has been analyzed. The diffraction efficiency, deflection angle and RF frequency required for the system have been determined.

Rare earth doped silica based fiber lasers and amplifiers with very high output power and excellent beam quality are efficient devices for a variety of applications in industry, science and medicine. During the last years, important progress was possible by new design concepts but also by carefully tailoring the material properties. Aspects of material and technology development concerning the interaction of different dopants and co-dopants will be discussed in the following. Our discussion concentrates on the optical properties of the laser fiber as refractive index, absorption and emission of the rare earths and especially on phenomena concerning the background loss of the fibers. We have found a strong rare earth specific loss component which remarkably depends on the kind and the ratio of the co-dopants. The relations of this background loss to material composition and fabrication technology are demonstrated and discussed on an empirical base.

Ion beam assisted deposition (IBAD) technique had widely used for improving stacking density and atomic mobility of thin films in many applications, especially adopted in optical film industries. Tantalum pentaoxide (Ta₂O₅) and silicon oxides (SiO₂) optical thin films were deposited on the quartz glass substrate by using argon ion beam assisted deposition, and the influences of the residual argon gas and thermal annealing processes on the optical property, stress, compositional and microstructure evolution of the thin films were investigated in this study. Ta₂O₅ thin films were analyzed by XPS indicated that the ratio value of oxygen to tantalum was insufficient, at the same time, the residual argon gas in the thin films might result in film and device instabilities. Adopting oxygen-thermal annealing treatment at the temperature of 425°C, the thin films not only decreased the residual argon gas and the surface roughness, but also provided the sufficient stoichiometric ratio. Simultaneously, microstructure examination indicated few nano-crystallized structures and voids existed in Ta₂O₅ thin films, and possessed reasonable refractive index and lower extinction coefficient. By the way, we also suggested the IBAD system using the film compositional gas ion beam to replace the argon ion beam for assisting deposited optical films. The designed (HL)⁶H6LH(LH)⁶ multi-layers indicated higher insertion loss than the designed (HL)⁶8H(LH)⁶ multi-layers. Therefore, using the high refractive index as spacer material represented lower insertion loss.

Amorphous silicon SOI-AWG device with 59% extra high refractive index difference (Δ) and the transmission spectrum of AWG's device indicated the insertion loss, crosstalk and side-lobe were lower than -3.5 dB, -25 dB and -45 dB, respectively, by 3D beam propagation method were investigated in this study. The smallest chip size of the whole device is smaller than 4.5 cm x 1.2 cm, and the highest coupling loss of the rib waveguide for single mode fiber was about -1.68 dB. Based on the simulation results, the device will be really fabricated by thin-film deposition, photolithography and dry-etching processes. Optical measurements of amorphous silicon films indicated, the more refractive index of a-Si films indicated possessing less point defects, dangling bonds, voids, and more hydrogen content and silicon nano-crystallized structures. Meanwhile, the more point defects, dangling bonds, silicon nano-crystallized structures, and less voids and hydrogen content result in larger extinction coefficient. Therefore, we adopted the suitable deposition rate and refractive index at 1550nm wavelength were 0.6 nm/s and 3.5012, respectively, to perform real AWG fabrication. From atomic force microscopy (AFM) analysis revealed the increased argon/silane flow rate and RF power wattage, and decreased operating vacuum would increase surface roughness. High-resolution transmission electron microscopy (HRTEM) analysis indicated amorphous silicon films mainly had amorphous structure with few silicon nano-crystallized structures, point defects and voids might affect the value of the refractive index and reliability. The structures of the a-Si films all indicated amorphous structure by x-ray diffraction (XRD) analysis.

Polyimides and polyimide-silica hybrid AWG device with 2.2% and 1.6% refractive index difference (□), and the transmission spectrum of AWG's device indicated the insertion loss were -3.12 dB and -3.16 dB, crosstalk were -20 dB and -15 dB, and side-lobe were both lower than -60 dB, respectively, by 2D beam propagation method were investigated in this study. The smallest chip size of the whole device is smaller than 3.4 cm x 1.8 cm, and the highest coupling loss of the rib waveguide for single mode fiber was about -1.02 dB. Based on the 3D simulation results, the devices will be really fabricated by thin-film deposition, photolithography and dry-etching processes. Optical measurements of polyimides and polyimide-silica hybrid materials formed on quartz glass indicated, the refractive indexes of top cladding/core/bottom cladding layers at 1550 nm wavelength were 1.522/1.546/1.522 and 1.4907/1.53/1.4907, respectively. The extinction coefficients of all samples indicated approximately zero at 1550 nm wavelength. We will adopt these polyimides and polyimide-silica hybrid materials to perform real AWG fabrication. From atomic force microscopy (AFM) analysis of polyimides and polyimide-silica hybrid materials revealed, the surface average roughness was 0.236 nm and 0.364 nm, respectively. The structures of polyimides and polyimide-silica hybrid materials were identified by fourier transform infar ray (FTIR). High-resolution transmission electron microscopy (HRTEM/EDAX) was used to study the localized interface structure and compositional distribution. The morphology of rib structure waveguides, polyimides and polyimide-silica hybrid films were examined by scanning electron microscopy (SEM).

In this paper, using semiclassical approach, we present a numerical simulation of light generation in one-dimensional (1D) photonic crystal laser based on SiO₂:Er³⁺ active medium with Fabry-Perrot (F-P) resonator. We use Transfer Matrix Method to study laser gain characteristics. Combination of TMM with semiclassical theory give us the lasers characteristics of small signal gain as a function of parameters: F-P mirrors reflectivity's, period of the photonic structure, geometry of the primitive cell as well as the number of the primitive cells creating the photonic crystal.

A Au/Cr/IZO composite thin film for application of thermal electrode of the waveguide devices is proposed. It can be fabricated easily on the glass-based waveguide devices by sputtering deposition process. The hardness and impedance properties, as well as its adhesion with the glass substrate are investigated in this study.

In this paper, for the first time we present semi analytical, approximate model of dynamic operation of one dimensional photonic crystal Nd³⁺:YAG laser. In our theoretical model, we take into account the gain saturation effect and longitudinal field distribution. With the help of time dependent laser rate equations, we obtain an approximate formulas relating the damping rate and frequency of relaxation oscillations and modulation bandwidth to the output power and laser parameters such as photonic crystal geometry, losses, and value of reflection coefficient of laser mirror. With this approximate formulas, we obtain the 1D photonic crystal laser characteristics, which reveal an optimal feedback strength for F-P cavity laser structure. With the help of this model it is possible to defined optimal geometry of the laser structures, which provides maximal modulation bandwidth for given pumping level (characterized by small signal gain).

With the development of all-optic network, the research of all-optic wavelength routing technology becomes a hot subject in all over the world. In this paper a new structure optical wavelength router which is feasible in the reality is proposed whose main advantage is having no tunable components and converting multiple wavelengths simultaneously. The proposed design is very similar to a traditional wavelength router structure, but the difference is in two fold. First it uses fixed wavelength converter. This converter converts any input wavelength to fixed wavelength. Second it allows loop back of the light. With this allowance of loop back, we can achieve the ability of tunable wavelength converter using fixed tuned wavelength converter. In comparison with previously reported structures, our design has the advantage of its simplicity and low-cost. The all-optic router prototype is experimentally tested in a small 3X3 network with a STM-16 bit stream per channel.

Pumping source is the key technology of fiber Raman amplifiers (FRA) which are important for ultra long haul and high bit rate dense wavelength division multiplexing (DWDM) systems. In this paper the research work of the project, "Fiber Raman Laser and Amplifier pumped by Nd³⁺:YVO₄ Solid State Laser", supported by the National High-tech Program (863-program) of China is introduced, in which a novel 14xx nm pump module with fine characteristics of high efficiency, simplicity, compactness and low cost is researched and developed. A compact 1342 nm Nd³⁺:YVO₄ diode pumped solid state laser (DPSSL) module is developed with the total laser power of 655mW and the slope efficiency of 42.6% pumped by a 2W 808nm laser diode (LD). A special C-lens fiber collimator is designed to couple the 1342nm laser beam into a piece of single mode fiber (SMF) and the coupling efficiency of 80% is reached. The specific 14xx nm output laser is generated from a single stage Raman resonator which includes a pair of fiber Bragg gratings and a piece of Germanic-silicate or Phospho-silicate fiber pumped by such DPSSL module. The slope efficiency for conversion from 1342 to 14xx nm radiation is 75% and the laser power is more than 300mW each. Finally, Raman gain experiments are carried out with 100km SMF. 100 nm bandwidth with 10dB on-off Raman gain and 1.1dB gain flatness is achieved by pumped at 1425, 1438, 1455 and 1490nm.

The study of steady states for ultrashort dissipative optical solitons, appearing in single-mode erbium-doped fiber amplifiers is developed. Such solitons are shaped due to resculpturing same external optical pulses because of the passive mode-locking process in traveling-wave regime. At the stage in our hand, we consider rather simplified model related to the most desirable practically fundamental solitons and, in so doing, develop extremely extended analytical approach. The analysis performed includes the already-known data for the model selected, generalizes them, and demonstrates that fiber amplifiers can support various sequences of optical pulses on a background as well as both dark and bright dissipative optical solitons, whose amplitude and frequency profiles in time are exactly described. Possible application lies in implementing an all-optical regeneration of ultrashort optical bit pulses in fiber links.

Optical waveguides were prepared by the incorporation of silver or copper ions using the classical staining. We used commercially available soda-lime silicate and borosilicate glasses as substrates. Silver or copper stain was applied on a side of the glass substrates. The substrates were heat-treated at elevated temperature for various times. The treated glasses were optically clear and almost colorless except for a few samples stained for longer time. This indicates that silver and copper metal nanoparticles and Cu₂O nanoparticles causing coloration of glasses were not formed in the glass substrates. The ion-incorporation process was approximately controlled by the diffusion of ions. We observed the propagation of 633 nm laser radiation by a prism coupling method showing that the glass surface region plays a role of waveguide. Refractive index change more than 0.01 at 633 nm was achieved in the waveguide layers.

We designed and fabricated a 1310 nm/1550 nm demultiplexer with a directional coupler for optical fiber communication systems with much increased transmission capacity. We also propose novel design methods to reduce its length and improve its performance. First, the device length was reduced by using the generalized extinction ratio curve, which was normalized by the normalized frequency (v). Second, the lateral shift and the curved waveguide for the optimization of input region were adopted to improve the extinction ratio, and the shift is to outward of a directional coupler. Lateral shift reduces discrepancy between the two transfer coefficients, Cve and Cvo, and curved input waveguide controls mode profile asymmetrically to minimize the effect of these without serious decrease in transfer efficiency. For a given interaction length of 1.948 mm, the 1310 nm and 1550 nm wavelength light transfer to the cross state and the bar state, respectively. Above results are used to fabricate of a demultiplexer operating at 1310 nm and 1550 nm with the extinction ratios of -29.64 dB at 1310 nm and -20.32 dB at 1550 nm, respectively. The demultiplexer device was fabricated with polymer materials on a fused glass substrate. The core of the device was formed by micro-transfer molding technique with the polydimethylsiloxane (PDMS) mold. We found that these novel devices can be formed in optical fiber communication systems.

The growth characteristics and properties of large size SrAlF5 single crystals are described and compared with those of BaMgF₄. Transmission spectra in the vacuum ultraviolet wavelength region indicate a high transparency of SrAlF₅ (about 90% without considering surface reflection loses) down to 150 nm, on contrast to the optical loses observed for BaMgF₄. The ferroelectric character of SrAlF₅ is evidenced by the reversal of the spontaneous polarization in a hysteresis loop. The higher potential of SrAlF₅ in comparison with BaMgF₄ for the realization of all-solid-state lasers in the ultraviolet wavelength region by the quasi-phase matching (QPM) technique is pointed out. SrAlF₅, besides a higher grade of transparency, shows a nonlinear effective coefficient similar to that of quartz and uniaxial nature, on contrast to the one order smaller nonlinear coefficient and biaxial character of BaMgF₄. The refractive index of SrAlF₅ from the ultraviolet to the near-infrared wavelength region is measured by the minimum deviation method. The Sellmeier and Cauchy coefficients are obtained from the fits to the curves of the ordinary and extraordinary refractive indices, and the grating period for the first order QPM is estimated as a function of the wavelength. The poling periodicity for 193 nm SHG from 386 nm is 4 micron-m.