The performance of Fourier transform optical processors, e.g. optical correlators, beam steering systems, associative memories, etc., depends intimately both on the physical characteristics of the particular spatial light modulator (SLM) and on the particular algorithms that map the signal into the available modulation range of the device. For the most general Fourier systems the information/signal is complex-valued. This is an essential requirement for multi- spot beam steering systems and composite pattern recognition filters. Since practical and/or affordable SLM's only represent a limited range of values in the complex plane (e.g. phase-only or quantized phase), numerous approaches have been proposed and demonstrated for representing, approximating, encoding or mapping complex values to the available SLM states. The best approach depends on the space bandwidth product of the signal, the number of SLM pixels, the computation time of the encoding algorithm, the time available for the application, and the quality of the optical processor, as measured by an application-specific performance metric. Based on the low pixel count and the high cost per pixel of most current SLM's we argue for encoding algorithms that map one signal value to one pixel value, as opposed to group-oriented encoding. This maximized the usable area of the frequency plane. We also recommend algorithms that maximize the fidelity over the entire frequency range as opposed to maximum diffraction efficiency/minimum mean squared error design. These ideas are illustrated with several simulated and experimental results for pseudorandom, minimum Euclidean distance, error diffusion and hybrid/blended encoding algorithms.

In automatic target recognition and machine vision applications, segmentation of the images is a key step. Poor segmentation reduces the recognition performance. For some imaging systems such as MRI and Synthetic Aperture Radar (SAR) it is difficult even for humans to agree on the location of the edge which allows for segmentation. A real- time dynamic approach to determine the quality of segmentation can enable vision systems to refocus of apply appropriate algorithms to ensure high quality segmentation for recognition. A recent approach to evaluate the quality of image segmentation uses percent-pixels-different (PPD). For some cases, PPD provides a reasonable quality evaluation, but it has a weakness in providing a measure for how well the shape of the segmentation matches the true shape. This paper introduces the complex inner product approach for providing a goodness measure for evaluating the segmentation quality based on shape. The complex inner product approach is demonstrated on SAR target chips obtained from the Moving and Stationary Target Acquisition and Recognition (MSTAR) program sponsored by the Defense Advanced Research Projects Agency (DARPA) and the Air Force Research Laboratory (AFRL). The results are compared to the PPD approach. A design for an optoelectronic implementation of the complex inner product for dynamic segmentation evaluation is introduced.

Automatic target recognition (ATR) is a mature but active research area. In an earlier paper, we proposed a novel ATR approach for recognition of targets varying in fine details, rotation, and translation using a Learning Vector Quantization (LVQ) Neural Network (NN). The proposed approach performed segmentation of multiple objects and the identification of the objects using LVQNN. In this current paper, we extend the previous approach for recognition of targets varying in rotation, translation, scale, and combination of all three distortions. We obtain the analytical results of the system level design to show that the approach performs well with some constraints. The first constraint determines the size of the input images and input filters. The second constraint shows the limits on amount of rotation, translation, and scale of input objects. We present the simulation verification of the constraints using DARPA's Moving and Stationary Target Recognition (MSTAR) images with different depression and pose angles. The simulation results using MSTAR images verify the analytical constraints of the system level design.

There are two extremes in optimization with little ground between them. They are local optimization and global optimization. Local optimization is normally very fast, but the optimum it finds may be far from the best (global) optimum. Global optimization is very slow, but it gives the best optimum- at least in principle. Using mammal herds as rough models, we suggest a new evolutionary method that has aspects of both and achieves intermediate results most of the time: faster-than-global convergence with better-than- local performance.

This paper introduces two new concepts into the field of particle image velocimetry. Traditionally, a particle image velocimeter is based on correlation operation between multiply exposed images. Cross-correlation operation is same as classical matched filtering (CMF) operation, which suffers from low peak intensity and power efficiency. Phase only filter (POF), because of its power efficiency and sharp correlation peak has been used extensively for pattern recognition. We propose to introduce POF instead of CMF for tracking high-speed particles. In addition, a powerful approach for particle tracking is introduced which involves tracking the particle in nine-directions. To track displacement of particles further away from original location, the original image is correlated with eight blocks around the original block. This enable us to track higher velocity particles. The method involves correlating two pictures taken some time apart. Phase only filter is used to correlate the original image with its time and space- shifted version to determine the velocity of the particles.

Photonic time-stretch has been proposed as a signal preprocessor to perform A/D conversion in otherwise inaccessible high frequency regimes. We have demonstrated time-stretching of MM-wave signals at frequencies up to 102 GHz down to 11 GHz , using an electrooptic modulator fabricated with the new polymer material PC-CLD. This application takes advantage of the inherent wideband capabilities of the PC-CLD material system, which has also demonstrated good optical insertion loss and high non- linearity at 1.55 micrometers . The dispersion penalty inherent to time-stretching imposes an additional bandwidth limit to that imposed by the modulator. A single-sideband modulator configuration is proposed to reduced the effect of this penalty.

The rapid development of ultra-wide bandwidth fiber optical communications networks has challenged circuit designers to obtain ever-increasing link gain-bandwidth products with new electro-optic modulators. As the link bandwidth increases, high power modulator drivers become very costly and have low efficiency. To overcome the limited gain-bandwidth product, it is important to reduce the required driving voltage or the so-called halfwave voltage of current electro-optic modulators. In this paper, we report results on new polymeric electro-optic modulators with a halfwave voltage of 0.8V and a halfwave voltage-interaction length product of 2.2V-cm. The low driving voltage allows electro-optic modulators to be driven directly by high-speed logic circuits without an amplifier. The driving electronics and the system cost can be significantly reduced when these modulators are implemented. Here, low halfwave voltage modulators are based on recent developments in materials and modulator fabrication technologies. The incorporation of a new second-order nonlinear optical chromophore CLD-1 in a poly(methylmethacrylate) matrix has a demonstrated electrooptic coefficient approximately 60 pm/V at 1318 nm wavelength. Using this material system and an optical push- pull modulator design, sub-1 volt Mach Zehnder modulators and temporal stability of these modulators will be reported.

Chromophore-containing polymeric electro-optic materials must satisfy many requirements before they can be considered for use in applications at telecommunication wavelengths (1.3 and 1.55 microns). These include large macroscopic electro-optic activity, low optical loss, and stability (thermal, chemical, and photochemical). Such materials must be capable of being integrated with silica fiber optics and semiconductor electronics. We discuss design of chromophores not only for large hyperpolarizability but also for low optical loss and for thermal and photochemical stability. The processing of these materials to maximize electro-optic activity while minimizing processing- associated optical loss is discussed. Device structures appropriate for minimizing insertion loss are discussed, as is the fabrication of such dvices and three-dimensional active/passive optical circuits. The identification of new structure/function relationships provide design criteria for future improvements as well as permitting better definition of the performance limitations that can be expected for polymeric electro-optic materials prepared by electric field poling methods.

Studies on the influence of chromophore geometry on electro- optic coefficient/loading density and poling efficiency reveal that chromophore optical loading density is largely defined by the shape of the center of chromophore, and bulky groups at the end of chromophore is not preferable for most efficient poling of chromophore dipole. An EO coefficient of 122 pm/V at 1.06 micrometers has been achieved as a result of the systematic chromophore geometry optimization. Even high EO coefficients are expected to realized in the near future. Practical Mach-Zehnder modulators have been fabricated using CLD-1/APC material and have shown good dynamic thermal stability (120 degree(s)C), low optical loss (1.67db?cm at 1.55 micrometers ), low modulation voltage (2.4 volt, 2cm modulation length), and high extinction ratio (26dB).

Thin film electro-optic materials have been synthesized by a novel electrostatic self-assembly (ESA) method. This wet chemistry synthesis method allows the molecular-level, layer-by-layer formation of multilayer thin and thick films of alternating anionic and cationic molecules and other materials. We have found that during the adsorption of dipolar molecules from solution to form a single molecular layer, the dipoles align themselves. In a multilayered material, this leads to multiple functionalities that require a noncentrosymmetric molecular structure such as active optical properties and piezoelectric behavior. Such properties are usually achieved in other materials by electric field poling. In this paper, we describe the precursor molecular chemistries that we have developed to make electro-optic thin films by this method, how the films are formed, the resulting molecular orientation within the film, and measured by electro-optic coefficients to date. We also describe how the ESA process precursor chemistry may be modified to allow the incorporation of noble metal nanoclusters to form flexible thin films with electrical conductivity on the order of that bulk metals. Such conducting films have been used to form electrode layers on prototype electro-optic devices.

Thin film electro-optic materials have been synthesized by a novel electrostatic self-assembly (ESA) method using both manual and automated processes. This paper discusses the reproducibility of such ESA-formed electro-optic thin films formed by both methods. Multiple films were fabricated based on the same layer-by-layer molecular design. They were evaluated using UV-vis spectroscopy and multiwavelength ellipsometry to demonstrate linear growth with the addition of layers, and to measure the thickness of the formed film. Their electro-optic coefficients have also been measured using Mach-Zehnder and Teng and Man approaches. Variations in the properties, including absorption, thickness and electro-optic coefficients, for all of the test samples are reported. We analyze possible causes for such variations, which include time-dependent differences in solution chemistry and differences between manual and automated fabrication processes. We further suggest approaches to both the solution chemistry and thin film design that may be used to limit the effect of such variations on the performance of electro-optic devices.

We have demonstrated an enhancement in the effective electro-optic (EO) coefficient of electrode poled nonlinear optical polymers using a conductive polymer cladding. We have also demonstrated the lowest poling voltage to date, 300 V, for a 2 micrometers thick NLO polymer core and 2 micrometers thick conductive polymer cladding structure asymmetric waveguide structure. With the cladding material more conductive than the core material, the majority of the applied poling voltage is dropped across the core, maximizing poling efficiency and, hence, realizing a higher EO coefficient. These results show promise for lower operating voltage devices.

We report on the design, the fabrication, the characterization and the demonstration of a scalable multi- channel free-space interconnection components with the potential for Tb/x.cm² aggregate bit rate capacity over inter-chip interconnection distances. The demonstrator components are fabricated in a high quality optical plastic, PMMA, using an ion-based rapid prototyping technology that we call deep proton lithography. With the presently achieved Gigabit/s data rates for each of the individual 16 channels with a BER smaller than 10^-13 and with inter-channel cross-talk lower than -22dB the module aims at optically interconnecting 2-D opto-electronic VCSEL and receiver arrays, flip-chip mounted on CMOS circuitry. Furthermore, using ray-tracing software and radiometric simulation tools, we perform a sensitivity analysis fo misalignment and fabrication errors on these plastic micro- optical modules and we study industrial fabrication and material issues related to the mass-replication of these components through injection-molding techniques. Finally we provide evidence that these components can be mass- fabricated in dedicated, highly-advanced optical plastics at low cost and with the required precision.

Parallel one-step addition (subtraction), multiplication, and division is proposed to perform the computation of complex functions such as the square root, logarithm, exponential, and other related operations. An optoelectronic correlator based architecture is suggested for implementing the proposed modified singed-digit (MSD) number system representations based. We utilized the symbolic substitution technique to reduce the number of the computation rules involved.

We introduce a new integrated solid-optics component, a X- cube, which can perform lossless beam-splitting and filtering functionality among four input beams. The X-cube can also be used for various wavelength-division multiplexing-based communication and interconnection applications, such as star-coupling, wavelength routing, and add/drop multiplexing. Our demonstrated fiber-interfaces X- cube opto-mechanical packaging shows an insertion loss of 2.1 dB, a uniformity ratio of 1.036 with a uniformity variance of 0.279.

A novel optoelectronic quotient-selected modified signed- digit division technique is proposed. The division method generates one quotient digit per iteration involving only one shift operation, one quotient selection operation and one addition/subtraction operation. The quotient digit can be selected by observing three most significant digits of the partial remainder independent of the divisor. Two algorithms based on truth-table look-up and binary logic operations have been derived. For optoelectronic implementation, an efficient shared content-addressable memory based architecture as well as compact logic array processor based architecture with an electron-trapping device is proposed. Performance evaluation of the proposed optoelectronic quotient-selected division shows that it is faster than the previously reported convergence division approach. Finally, proof-of-principle experimental results are presented to verify the effectiveness of the proposed technique.

Arbitrary-phase-modulated array illuminator (APM-AIL) based on Talbot effect means that arbitrary-phase-modulated phase plate may generate the specific intensity distribution at the specific fractional Talbot distance. The previous understanding is that only the specific phase modulated Talbot illuminator is possible for this purpose. In this paper, we discussed how the condition of APM-AIL can be fulfilled. We found that APM-AIL is also a position- selective Talbot array illuminator, which is usually impossible to realize for the conventional Talbot illuminator. We have given two-dimensional experimental example of Talbot illuminator. We also present some of other experimental examples fabricated by binary-optics technology, e.g., nonseparable hexagonal illumination, random-intensity simulation of sky stars, optical square- beam transformation, and 1x3 beam splitting for readout of optical disk.

Optical interconnections and integrated optoelectronic devices are expected to be promising candidates that solve the lack of interconnection bandwidth between large-scale integrated circuits (LSIs). However, although two- dimensional parallel devices such as vertical-cavity surface-emitting lasers (VCSELs) and spatial light modulators (SLMs) have massive parallelism, their capabilities are not fully utilized without appropriate way to yields high speed processing. From the viewpoint of system and algorithm, the improvement of the physical layer by optical technologies should require the reconsideration of the architectural design and algorithms so that enough performance improvements could be obtained. In this paper, we will present several of our optoelectronic parallel computing systems including a two-layer pipelined parallel system, which is called OCULAR-II. The system uses VCSELs and phase modulation SLM for realizing free-space reconfigurable optical interconnects. The algorithmic approach is discussed including the optimal load allocation for optically interconnected systems and a novel database management algorithm. As one of the most important technological challenges, the alignment problem of optical beam is also investigated.

This paper will report the theoretical study and design of optical logic gates and functions using micromechanical phase-shifting gate technology for the first time, and will also cover the proposed fabrication process for these devices. Micromachined phaseshifting gate technology has been used to design micromechanical optical modulators. The basic principle of this technology is to utilize optical interference effects to modulate the light. Since silicon is highly transparent at wavelength of 1.55 micrometers , which is commonly used in optical communication. The phase-shifting gate is fabricated from silicon using standard microelectromechanical systems (MEMS) techniques. The gate is electro-statically or electro-thermally actuated by microactuators integrated on the same chip to realize the modulation of the light. Assume the logic value is 1 when the light transmittance through the gate is bigger than 70%, logic value is 0 when the transmittance is less than 30%. Otherwise, the logic value is undetermined, namely in transition region. Optical logic gates (AND, OR, NOT, etc) and optical functions (Half Adder, Full Adder, etc) can be readily constructed using this technology. The principle of these logic components is modeled, simulated using Matrix Optics Method. Their optimized design and performance is provided using a CAD program based on layered structures developed in MATLAB. Proposed fabrication process for these devices is also included.

We have demonstrated a simple method for controlling the nonlinear oscillations using only semiconductor lasers and photodetectors. An electro-optical NDFS (nonlinear delayed feedback system) has been composed by making use of this method. With this system, multi-stable oscillations and chaotic transitions with various patterns have been observed. In addition, some characteristic routing sequences form period-doubling bifurcation to chaos have been reproducibly observed when some external modulations with acoustic frequencies are applied to the NDFS. In this case, we have proved that the harmonic numbers of the multi- stable oscillation modes to appear as system output are to be controlled in terms of timing (phase) as well as frequencies of external input signals at the moment they are applied. And we have also confirmed such remarkable transition behaviors of the multi-stable oscillation modes by numerical analysis based on nonlinear delayed differential equations describing our NDFS. Consequently, we have demonstrated that the oscillation harmonic numbers can be directly chosen from the 1st order up to the 9th by setting the frequencies of the external input signals to be their characteristic values specifying the desired harmonic numbers to appear for output and also by setting the timing of input signals with respect to the phase of original waveform of the oscillating modes. Thus, our system is expected to be a potential for something novel, intelligent communication technique based on chaos.

In this paper we present different configurations for a compact free-space optical interconnection (FSOI) module by combining two radial gradient refractive index lenses (GRIN) and/or two arrays of refractive microlenses. Based on our finding with ray-tracing and radiometric analysis we discuss how we have selected the proper optical system configurations and how we have chosen the different design parameters to optimally accommodate different types of opto- electronic emitters such as LEDs, micro-cavity LEDs and VCSELs. We hereby focused on maximizing optical coupling efficiencies and misalignment tolerances while minimizing inter-channel cross-talk. Furthermore we discuss the experimental optical characteristics of two such prototype modules that we completed together with the first experimental results of their use in parallel data communication demonstrator systems.

In the form of micro-particles europium doped alkaline earth sulfides have been shown to exhibit high density of permanent spectral holes. The photon-gated spectral holeburning (PGHB) in these systems provided the most promising characteristics of any material known to date. These spectral holes can be used as optical memory. However, for any optical storage device either large size single crystals or thin films are required. Thin films of these materials are grown by Pulsed Laser Deposition (PLD) technique. This fast and simple growth technique is superior the single crystal growth or the molecular beam epitaxy (MBE) as far as the holeburning properties are concerned. Transparent glassy MgS:Eu and CaS:Eu films have been grown and tested for the spectral holeburning properties. Critical parameters such as the relative concentration of Eu²⁺ and Eu³⁺, and optical quality of thin films have been investigated. Int his paper we report on the growth and the high-density optical holeburning in these films. The density of spectral holes has been further increased by burning in multiple Eu-centers in a material and by depositing multiple layers of thin films of different materials in a stack.

The trinary signed-digit (TSD) number system is of interest for ultra fast optoelectronic computing systems since it permits parallel carry-free addition and borrow-free subtraction of two arbitrary length numbers in constant time. In this paper, a simple coding scheme is proposed to encode the decimal number directly into the TSD form. The coding scheme enables one to perform parallel one-step TSD arithmetic operation. The proposed coding scheme uses only a 5-combination coding table instead of the 625-combination table reported recently for recoded TSD arithmetic technique.

A novel technique that employs phase encoding for the reference image and nonlinear Fourier plane apodization for optimizing the detection performance for multiple target detection is proposed. The proposed reference phase-encoded JTC overcomes false target detection by eliminating the false correlation peaks while alleviating the effects of noise and other artifacts in just one-step thus ensuring higher processing speed. Also, this technique yields only one peak per target instead of a pair of peaks produced by alternate JTCs. An all-optical implementation for the reference phase-encoded JTC technique is proposed and computer simulation results are presented.

Photorefractive doubly doped Fe:Mn:LiNbO₃ crystal is the most promising material to record nonvolatile photorefractive holograms by photochromic effect, and is very useful for the reconfigurable integration of miniaturized optical 3-D systems within a crystal substrate. In this paper by recording few nonvolatile and spatially- local holographic gratings in a single block of photochromic Fe:Mn:LiNbO₃ photorefractive crystal, we presented a new technique to implement miniaturized Mach-Zehnder interferometer sensor integrated in bulk sample(s). The interferometer was self-adaptive and used to detect or monitor the temperature changes as one arm of the interferometer is exposed in a thermal field. The design and analysis on the performance are shown, and the experimental results are given. This sensor has the advantage of simple construction over the conventional sensor and optical fiber sensor.

An equation is given to study the time dependence of the Fresnel diffraction field of a grating illuminated by an ultrashort pulsed-laser beam. Through numerical calculation, we find the temporal Talbot effect is both time-dependent and distance-dependent. For the width of the input pulse (Delta) (tau) within a few decade femtoseconds, the shorter Talbot distance, and/or the longer length of the input pulse, the more similar the outline of the temporal intensity distribution to that of the input pulse. While for (Delta) (tau) within a few thousand femtoseconds, the outline of the temporal intensity distribution is almost the same as that of the input pulse except for a time-delay.

Free-space interconnections for optical computing and information processing require an understanding of the three dimensional propagation of ultrahigh bandwidth optical pulses. Unlike optical fibers that are basically waveguides, free space propagation involves additional phenomenon such as self-focusing. In order to understand the properties of unguided or free space propagation for interconnections it is necessary to use a three dimensional spatial grid as well as the usual temporal grid. We derived an expression for the propagation of free space optical pulses for data rates on the order of hundreds of terabits/sec. Our formulation incorporates physical parameters such as the pulse duration, pulse intensity and free space characteristics. Numerical calculations show the spatiotemporal pulse distortion for free space propagation.

Optoelectronic logical gates NAND and NOR are composed of thin film photoconducting and electroluminescent elements, made of cadmium sulphide and zinc sulphide respectively, doped with copper, chlorine and manganese. These gates consist of several photoconducting elements and one electroluminescent element connected in series or parallel, supplied with a sinusoidal voltage. In such a circuit the function of logical product or logical sum for input light signals illuminating the photoconducting elements is realized, and the output signal is the light emitted by the electroluminescent element. This output signal illuminates in turn the next photoconducting element being present in the second circuit, in which the NOT function is realized.

Nonlinear morphological correlation provides some better performances in pattern recognition than linear correlation. However, it requires considerable amount of computational effort to obtain the final result. An adaptive threshold decomposition technique is proposed to reduce the computation and increase the processing speed. Computer simulation shows that the proposed method yields similar results to the original morphological correlation but with much less computational effort. A visual-area-coding technique is proposed to implement the morphological correlation optically in a single step. This alternative optical implementation provides several advantages over the optical morphological correlation schemes.

Previously we have reported the largest number of photon- gated spectral holes ever burned in a solid. This has interest in their applications in optical storage. However, multiple holeburning in MgS:Eu resulted in noticeable erasure of the previously burned holes. This was attributed to the mechanism of holeburning in this material where both Eu²⁺ and Eu³⁺ are stable ions. In gated holeburning, Eu²⁺ ions are ionized. Eu³⁺ that form deep traps, capture the electrons generated during the holeburning and are converted to Eu²⁺. The Zero Phonon Line (ZPL) of these newly formed Eu²⁺ ions are randomly distributed across the inhomogeneous line causing a partial erasure of the holes burned earlier. This reduces the efficiency of holeburning. Co-doping of MgS:Eu and CaS:Eu with different rare earth (RE) ions has been investigated to provide deep electron traps other than Eu³⁺. Furthermore, co-doping provides the opportunity to burn holes in multiple ZPLs belonging to different REs, thus increasing the storage density many folds.