We analyze and simulate the optical properties of the frequency hopping wavelength division multiplexing (WDM) laser. In order to design the multi-channel wavelength hopping laser as the light source of optics to the x(OTTx), our investigation describes how to design, simulate of 64×64 Array Waveguide Grating (AWG) on the silicon-on-insulator (SOI) substrate. The achieved AWG has a channel spacing of 0.4 nm (50GHz) with its spectrum centered at 1550.52 nm. The number of arrayed waveguides is 266 and the length difference is 9.89μm. We find out an optimal value of waveguide separation at the junction between arrayed waveguides region and free propagation region. In order to get a better uniformity for 64 channel outputs while insertion loss and crosstalk are taken into account, we also describe the improved design by using tapered waveguide structure at the both ends of AWG. The experimental results show the flatness can be improved to 0.71 dB which is very close to our previous simulation works. We also analyze the concentration effect of doping Er, cross-talk and thermal effect in SOI waveguide. We investigate the optical sphericity mirror station (BS) and relay station (RS) in OTTx system. We use the uniformity for 64 channel outputs as the light source of wavelength hopping laser of this system. The optic signals convert to the receiving signal by 4G over OTTx signal converting technique in this system.

Dense wavelength division multiplexing (DWDM) networks are very attractive with applying development of arrayed-waveguide grating (AWG) N x N multiplexers. This AWG multiplexer device plays an important role in WDM networks because of its unique N input and N output geometry. We design and analyze an integrated 32×32 arrayed waveguide grating wavelength switch based on SOI waveguides. We demonstrate three application of 32×32 arrayed waveguide grating, such as: Multiplexing/Demultiplexing, Optical add/drop multiplexing (OADM) and wavelength switch. The 32×32 arrayed waveguide grating is designed with including phase modulator. The simulation result and working principle for output channel wavelength shift is matched. In order to improve AWG switch, we integrate AWG switch and multimode interference (MMI). AWG with MMI switch coupler was connected at the end of the input waveguide. Beam propagation method with FDTD method are utilized for simulation works. The deviation of crosstalk and insertion loss value is small, and specifically the crosstalk is lower than -30 dB.

We use the fiber loop mirror to form a cavity in our laser system, and two 1.5 μm semiconductor optical amplifier (SOA) also be used as a gain material in the cavity. We analyze the lasing power, SMSR, L-I curve and the stability of our designed symmetric resonator laser with various driving current of the SOA. According to our measured results, we can find that the polarization states of our lasers are stable and the output side-mode suppression ration (SMSR) of our laser is large. We successfully designed a symmetric two-way multi-wavelength wavelength-division-multiplexed (WDM) resonator laser system. The multi-wavelength continuous-wave(CW) fiber laser by utilizing the Fabry-Perot resonance can be applied to PolSK fiber-optic communication systems.

Two-dimensional 1×3 photonic crystal power dividers in a square lattice of dielectric columns are proposed for equal-power splitting at 1.55 μm wavelength. Dielectric columns having different radius are used for impedance matching such that high power transmission and equal-power division can be realized. Two proposed structures having normalized total transmitted powers as large as 0.99 are successfully designed.

Based on the electro-optic and piezoelectric effects, principle of a 2×2 bypass-exchange switch in photorefractive LiNbO₃ crystal is discussed. In photorefractive volume grating, the Bragg condition can be deviated by applying a specific field during readout. That is, by applying a specific field E_s or zero field, the diffraction efficiency will be 0 or 1, and this property can be used to realize the exchange or bypass operation of the switch. In this paper, on considering both the piezoelectric and the electro-optic effects caused by the applied electric field, we analyzed relations of both the specific field and the incident intensity ratio with respect to the writing angles and polarizations of writing beams.

In this paper, our recent works on dynamic light field synthesis engineering using spatial light modulators are presented. The combination of optimization techniques in theoretical design methods and experimental methods with spatial light modulators is a main motivation of our study. The firstly discussed system is the genetic feedback tuning loop for the optimal system tuning and aberration compensation. The genetic algorithm is embedded into the light field synthesis system and the iterative system tuning procedure is devised for optimizing and tuning the real system. The secondly introduced topic is the experimental implementation of the iterative fractional Fourier transform algorithm for designing the phase profiles of phase holograms. The ath fractional Fourier transform and its inverse transform is optically implemented. The light field synthesis systems with optically implemented iterative fractional Fourier transform are proposed. In the proposed systems, using the phase-shifting digital holography technique, the phase profile of real light field is measured, and with phase spatial light modulator the light field is generated. It is shown that the diffraction image measured at each iteration step evolves to the optimal goal. Some experimental results validating the proposed schemes are presented.

In this paper, we present novel designs for all optical analog-to-digital converters simulated and realized in photonic crystal platforms. The designs presented were implemented on both photonic bandgap based structures as well as self collimation based structures. Numerical simulation results as well as fabrication results are also included. Characterization results validate the designs presented for a functional all optical two bit analog to digital converters in photonic crystals. The design presented can be further scaled to higher resolution conversion as well as to no optical frequencies if necessary.

High-speed optical synchronization signal generation high speed computer is very important. The rational harmonic (RH) modelocking scheme is a useful technology to generate pulses at a repetition rate higher than the modulation frequency. In this paper, we design an amplitude modulated mode-locked figure eight fiber laser as a 50 GHz optical pulse. In the cavity of high speed laser source, we utilize an amplitude modulator and phase modulator to inject additive modulation signal respectively. The modulation signal can let the longitudinal mode in cavity produce constructive interference, and then, achieve small modulation signal to excite harmonic and rational mode-locked laser in high repetition rate. The pulsewidth is 13.1ps with feeding a 16.4dBm, 12.5002248GHz modulation signal to the amplitude modulator. The pulsewidth, rise time and falling time of the 50GHz optical pulse are adjustable under experimental verification. In optical transmission systems, we consider the 50GHz optical pulse used in the optical interconnection transmission analysis.

We propose an optical implementation of iterative Fourier transform algorithm using a spatial light modulator and phaseshifting digital holography technique. It is shown that the optically implemented iterative Fourier transform system can improve quality of target diffraction images in real time by the same way the numerical iterative Fourier transform algorithm does in the numerical simulation. In the proposed implementation, the wave front of diffraction field is directly measured by the phase shifting digital holography technique and the phase modulation of light field is performed by a phase-type spatial light modulator. The feasibility and more general applicability of the proposed implementation of the iterative Fourier transform algorithm for digital holography techniques are discussed.

In this paper, silicon-based micro and subwavelength optical elements based on a free-standing silicon nitride (SiN_x) membrane are achieved. These elements, including gratings, microlenses, and holographic optical elements (HOEs), are designed and used within the visible and infrared regions. These devices can be used as collimators, reflectors, and wavelength-dependent filters with advantages of simple structure, high efficiency and feasibility to integrate with other elements into a micro-system chip. In order to demonstrate the advantage of micro-optics of free-standing SiN_x membrane type in integration, a miniaturized optical pickup head module based on a stacked micro-optical system is developed. This module consisted of a laser diode, a reflector, a grating, a holographic optical element, and some aspherical Fresnel lenses. The novel microoptical system can overcome the problems encountered in other microoptical systems such as off-axis aberration, lower optical efficiency or durability, integration and even in fabrication. A focal spot with a FWHM diameter of 3.3 μm is obtained while the diffraction limited full-width at half-maximum (FWHM) is 0.7 μm. To extend the advantage of micro-optics of free-standing SiNx membrane, the subwavelength optical elements base on guided-mode resonance is also developed. With various Si-based structures, the filter possesses numerous properties such as variable bandwidths, low sideband, flattop, and etc. They are also applied as biosensors to detect the hybridization process of bio reaction for their high sensitivity. The results show that micro and subwavelength optical elements fabricated on Si-based material will be a candidate for emerging silicon micro-photonics.

Alexandrite crystal is commonly used for making alexandrite laser, and it also has a less-known phenomenon called the alexandrite effect that refers to the color change between different light sources. A novel spectropyrometer for temperature measurement of a radiating body utilizing the alexandrite effect is introduced. The alexandrite effect method for temperature measurement is based on the relationship between the temperature of blackbody and the hue-angle in the CIELAB color space. The alexandrite effect spectropyrometer consists of an optical probe, a spectrometer, a computer, and an alexandrite filter. It measures the spectral power distribution of a radiating body through the alexandrite filter, calculates the hue-angle, and determines the temperature. The spectropyrometer is suitable for temperature measurement of any radiating body with or without spectral lines in its spectral power distribution from 1000 K to 100000 K. The spectropyrometer is particularly useful for high to ultrahigh temperature measurement of any radiating bodies with spectral line emissions, such as electric arcs and discharges, plasmas, and high temperature flames.

In this paper, we propose a novel Coplanar Waveguide (CPW) Frequency Division Multiplexer (FDM) using Photonic Band Gap (PBG) cell concept. The output frequency and phase responses of these FDMs are also demonstrated. The output frequency bands of our designed one by three FDM include: 1.1 GHz ~ 2.1 GHz, 1.9 GHz ~ 3.7 GHz, 4.4 GHz ~ 7.3 GHz; three various ranges. The theoretical analysis and experimental results show good coincidence. The three-band PBG-CPW FDM can be effectively size reduced for achieving monolithic microwave integrated circuits (MMIC) in the future. In other words, this FDM component can be more widely and flexibly applied in microwave communication system.

Lots of attention has been paid to the optical bistability in fiber optical because its potential application in optical information processing and fiber optical communication. Recently the optical bistability in erbium-doped active fiber induced by the nonlinear absorption of the fiber has been investigated. In this paper, we demonstrated the strong optical bistability in the ytterbium-doped fiber laser with the pump-bypassed cavity configuration. In this original configuration, the fiber laser is divided into the gain stage and absorption stage by a WDM. As the function of incident pump power, both the 976nm residual pump intensity and the 1040nm laser signal of this laser exhibit ~320mW-wide optical bistabilities in an antiphase manner with respect to each other. Further the residual pump power is directed to pump the second Er and Yb co-doped fiber laser cavity to generate the lasing at 1537nm. As a result of the optical bistability in the residual pump, the lasings of 1040nm and 1537nm are switchable between each other. Worthwhile to point out, these two wavelengths are located in the two wavelength windows applicable for the free-space laser communications, respectively. Therefore the switchable 1040 and 1537nm source by combining the bistable feature of Yb fiber laser with the hybrid cavity configuration (pump-bypassed cavity plus the bifurcated cavity could have important application at this aspect.

We demonstrate that, by using circular array of electrode pattern and applying multi-level phase modulation in each zone, a high-efficiency switchable electro-optic diffractive lens using liquid crystal as the active medium can be produced as a switchable eyewear. The lens is flat and the thickness of the liquid crystal is 5 μm. Two different designs are presented. In one design, all the patterned electrodes are distributed in one layer with a 1-μm gap between the electrodes. In the other design, the odd- and even-numbered electrodes are separately patterned in two layers without any lateral gaps between the electrodes. In both cases, vias are made for interconnection between the electrodes and the conductive wires. With the one-layer electrode design, both 1-diopter and 2-diopter 8-level lenses are demonstrated with an aperture of 10 mm. With the two-layer electrode design, a 2-diopter, 15-mm, 4-level lens is demonstrated. The diffraction efficiency of the 8-level lens can be higher than 90%. The ON- and OFF-state of the electrically controlled lens allow near- and distance-vision respectively for presbyopic eyes. The focusing power of the lens can be adjusted to be either positive or negative. The focusing power of the 8-level lens can be adjusted for near-, intermediate-, and distance vision. The lens is compact and easy to operate with fast response time, low voltages and low power dissipation. This is the first demonstration of the switchable lenses that almost meet the requirements for spectacle lens.

A strongly focused laser beam can be used to trap, manipulate and exert torque on a microparticle. The torque is the result of transfer of angular momentum from the laser beam. The laser could be used to drive a rotor, impeller, cog wheel, etc. of a few microns in size, perhaps fabricated from a birefringent material. We review our methods of computationally simulating the torque and force imparted by a laser beam. We introduce a method of hybridizing the T-matrix with the finite difference frequency domain (FDFD) method to allow the simulation of materials that are anisotropic and inhomogeneous, and structures that have complex shapes. We also employ an alternative discrete dipole approximation method. The high degree of symmetry of a microrotor, such as rotational periodicity, could be exploited to reduce computational time and memory requirements by orders of magnitude. This is achieved by performing calculations for only a given segment that is repeated across the whole structure. This can demonstrated by modeling the optical trapping and rotation of a cube.

Design of diffractive optical element for generating desired optical intensity distribution on an arbitrarily curved surface is investigated. The diffracted field distribution on a curved surface generated by a diffractive optical element is described by the non-invertible Fresnel transform. The conventional iterative Fourier transform algorithm is inappropriate for the design problem with the non-invertible Fresnel transform. The practical applicability of the nonlinear conjugate gradient method for this design problem is studied. It is shown that the nonlinear conjugate gradient method is practicable and effective for this kind of diffractive optical element design.

Single mode SOI waveguide devices with low propagation loss and low insertion loss have been demonstrated at wavelength λ=1.3μm and 1.55μm, respectively. The wavelength resonator devices have many applications in optical communications including wavelength filtering, routing, switching, modulating, multiplexing, optic buffer, and demultiplexing. We use the free carrier plasma dispersion effect to design the switch of SOI buffer and Photonic crystal Bandgap (PBG) waveguide buffer devices are simulated by Finite Difference Time Domain (FDTD) methods. The technology have made it possible to create micrometer-size photonics devices based on reasonably low-loss semiconductor waveguides. To characterize SOI buffer waveguides delays, the analysis of wavelength response, the number of propagation modes and the waveguide loss are investigated at wavelength 1.55μm.

Information techniques featuring adaptability, autonomy, and diversity found in the behavior of livings are promising. The purpose of this study is to explore object selection method adaptable to unexpected change of the environment. An attractor selection is used as an algorithm for flexible adjustment to various change of the environment. An attractor is a convergence point in a state space and corresponds to a stable point of a given system. The attractor selection chooses an attractor according to the suitability for a given environmental condition. The proposed object selection algorithm finds a solution from several images captured with different focus settings. To obtain these images a compound-eye imaging system is assumed to be used. In the object selection, an object is regarded as an attractor. The location and the features of the object are expressed as variables in the state space. In this study, hue in the Hue-Saturation-Value color model is used as a parameter of an environmental condition. In the simulation, two objects of different hue were located at different distances. One of the objects might be selected by the proposed algorithm. The correct operations of the algorithm are confirmed. The results show that the attentive object is correctly switched according to the change of selecting condition. The adaptability and the robustness of the method has been confirmed.

This paper presents a method for performing model-based motion estimation for ground tracking from an airborne video. Different model geometries are used for the input into a four-step search (4-SS) motion estimation algorithm. The algorithm allows the user to select both the model geometry and the center mass of the vehicle. The estimated center of mass is determined from the 4-SS motion estimation and used as the input for the comparison between the next two images in the sequence. The model geometries considered are a rectangle internal to the vehicle, a rectangle external to the vehicle, or a polygon that matches the general shape of the vehicle. Each geometry is compared against ground truth data. A goodness measure is used to compare tracking quality. Initial results indicate both geometries track well as long as the model geometry is adjusted based on aircraft motion and as long as variations such as specularities are kept to a minimum.

One of the major problems in automatic target recognition (ATR) involves the recognition of images in different orientations. In a classical training-testing setup for an ATR for rotated targets using neural networks, the recognition is inherently static, and the performance is largely dependent on the range of orientation angles in the training process. To alleviate this problem, we propose a reinforcement learning (RL) approach for the ATR of rotated images. The RL is implemented in an adaptive critic design (ACD) framework wherein the ACD is mainly composed of the neuro-dynamic programming of an action network and a critic network. The proposed RL provides an adaptive learning and object recognition ability without a priori training. Numerical simulations demonstrate that the proposed ACD-based ATR system can effectively recognize rotated target with the whole range of 180° rotation. Analytic characterization of the learning algorithm provides a sufficient condition for its asymptotic convergence. Finally, we obtain an upper bound for the estimation error of the cost-to-go function under the asymptotic convergence condition.

Identification of significantly differentially expressed genes (marker genes) among sample groups is a central issue in microarray analysis. This identification is important to understand the molecular pathway of diseases. Many statistical methods have been proposed to locate marker genes. These methods depend on a cutoff value for selection. A tightfisted cutoff may omit some of the important marker genes, whereas a generous threshold increases the number of false positives. Although robust models for identifying marker genes more accurately is an area of intense research, effective tools for the evaluation of results is often ignored in the literature. Despite the robustness of many of these methods, there is always some probability of false positives. In this paper, we propose a novel approach that exploits parallel coordinates to visualize the gene expression patterns so that one can compare the expression level changes of the marker genes between sample groups and determine whether the selected marker genes are valid. Such visualization is useful to measure the validity of the marker gene selection process as well as to fine tune the parameters of a particular method. A prediction method based on the selected marker genes is used to measure the reliability of our process.

A fully automated application was developed and used for the registration of T1-weighted magnetic resonance images (MRIs) for Alzheimer patients. Two methods for image registration were implemented and compared: affine and nonlinear registration. Nonlinear registration uses continuum-mechanics-based elastic deformation. The affine registration algorithm is linear and is generated by an amplitude-modulated phase-only filter. The nonlinear registration method uses an elastic transformation generated by Navier-Stokes continuum-mechanics models. The validation method to quantitatively compare the performance of the affine and nonlinear registration algorithms uses root-mean-square error and three-dimensional volume rendering.

Fiducials imprinted on laser beams are used to perform video image based alignment of the beams in the National Ignition Facility (NIF) of Lawrence Livermore National Laboratory. In any laser beam alignment operation, a beam needs to be aligned to a reference location. Generally, the beam and reference fiducials are composed of separate beams, as a result only a single feature of each beam needs to be identified for determining the position of the beam or reference. However, it is possible to have the same beam image contain both the beam and reference fiducials. In such instances, it is essential to separately identify these features. In the absence of wavefront correction or when image quality is poor, the features of such beams may get distorted making it difficult to distinguish between different fiducials. Error checking and correction mechanism must be implemented to avoid misidentification of one type of feature as the other. This work presents the algorithm for multi-object detection and error correction implemented for such a beam line image in the NIF facility. Additionally, we show how when the original algorithm fails a secondary algorithm takes over and provides required location outputs.

Fiducials in the form of intersecting straight lines are used to align the target in the final target chamber of the National Ignition Facility of Lawrence Livermore National Laboratory. One of the techniques used to locate these lines is the Hough transform. When two lines intersect at a 90 degree angle, it is tempting to orient the lines to horizontal and vertical directions. There are other possible angles at which the lines may be oriented. One question that arises while designing the fiducials is whether there is a preferred angle or range of angles that leads to higher accuracy. This work attempts to answer this question through detailed computer simulation.

A finite element formulation is developed for solving the problem related to thermoelastic damping in MEMS beam resonators. The perturbation analysis on the governing equations of heat conduction, thermoleasticity and dynamic motion yields a linear eigenvalue equation for the exponential growth rate of nodal temperature, displacement and velocity. The numerical solutions for a simply supported beam have been obtained and compared to the analytical solutions found in literature, showing excellent agreements. The finite element formulation in this work has advantages over the existing analytical approaches in that the method can be easily extended to general three-dimensional geometries.