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The article describes the design and performance of an InGaAsP-InP 1 x 2 reconfigurable waveguide digital optical switch (RW-DOS) actuated by carrier-induced refractive index modulation. The optimized InGaAsP-InP devices are found to have required less than 20-mA drive current and exhibited better than 25-dB switching contrast ratio.

Camera motion estimation in image sequences generally focuses on the recovery of the frames when the camera is mounted on a moving platform. Global motion in video sequences is more complex and involves camera operation, camera motion, and other nontarget motions. Global motion compensation is usually handled by compensating the dominant motion using estimation and segmentation techniques. To enhance tracker performance and accuracy, frame recovery operation plays a crucial role by estimating undesired motion. In this paper, a normalized correlation-based regional template-matching (TM) algorithm has been developed to accurately recover frames before the application of the tracking algorithm. Then, a robust multiple-target-tracking system has been developed using a combination of fringe-adjusted joint transform correlator and TM techniques. Joint transform correlation detects a target optoelectronically, while TM technique is performed digitally. To increase the tracking system speed and decrease the effects of clutter, a subframe segmentation and local deviation-based image-preprocessing algorithm has been proposed. The improved performance of multiple-target-tracking system is tested using real-life forward-looking infrared (IR) imagery video sequences obtained from IR sensors mounted on an airborne platform. Index Terms--Fringe-adjusted filter (FAF), global motion compensation, joint transform correlation (JTC), optoelectronic target detection technique, target tracking.

In recent years, optical technology has been incorporated into mechatronic systems at an accelerated rate, and as a result, a great number of machines/systems with smart optical components have been introduced. This integrated technology is termed 'optomechatronics.' This paper introduces the fundamental concept, definition, and characteristics of the technology by analyzing the characteristics of a variety of practical optomechatronic systems. The introduction describes how optical and mechatronic components are physically coupled to each other to form optomechatronic integration. With this observation, we describe the nature and integration concept of the technology, from which we can derive the technology-driven fundamental functionalities in some detail. Based upon the knowledge on basic optomechatronic integration and functions, we analyze optomechatronic systems in general from the viewpoint of system configuration and design and, thus, the roles of optical technology in overall system performance being learned and the synergistic effects due to its fusion with mechatronics being understood. Index Terms--Functional modules, mechatronics, optoelectronics, optomechanics, optomechatronic integration, technology fusion.

A physical modeling and a rigorous theoretical analysis consisting of the two-temperature model and the generalized transmission-line model is used to evaluate a photo-induced terahertz continuous-wave voltage from a dc current-biased high-temperature superconducting (HTS) transmission line by optical heterodyne photomixing. The electrical and optical frequency-response analyses show the amplitude of this voltage increases with increasing beat frequency and decreasing optical frequency of laser beams. Its maximum frequency is found to be limited by the gap frequency of the HTS material, which is consistent with the available experiments reported in the literature. The developed model along with our numerical simulation reveal the ways to produce a coherent traveling-wave and high-power terahertz signal with proper choice of an HTS material, bias condition, geometrical configuration, and parameters of the transmission line and characteristics of two laser beams. This FITS photomixer can play an important role in terahertz transceivers as broadly tunable local oscillators with low-noise/low-power consumption characteristics. Index Terms--Photomixers, superconducting devices, superconducting optoelectronics, terahertz devices, terahertz photonics.

A wave demultiplexer with N channels in a two-dimensional photonic crystal is described and discussed.

Research into the optical perturbations of electrical conduction processes in aqueous solutions by laser-produced plasmas is presented. The perturbation of the conduction process following the plasma formation can be seen as a voltage pulse between the electrodes of the conduction cell.

Research describing ways of enhancing the quantum-well intermixing is presented. Particular attention is given to the method of He-plasma assisted epitaxy. Experimentation involving gas source molecular beam epitaxy is discussed with focus on achieving optoelectronic devices.

Terahertz pulses were measured using chirped pulse technology.

A numerical analysis of the modulation characteristics of transverse multimode vertical-cavity surface-emitting lasers is presented.

A demonstration of a new multiloop technique for an optoelectronic oscillator to solve the associated RF filter problem is presented.

A study on asymmetric integrated optical Y-branches proposes the use of single-mode asymmetric Y-branches using microprisms to enhance their performance as compared to conventional single-mode asymmetric Y-branches. The configuration of the suggested asymmetric Y-branch, 3-dB power divider is presented. Applications of asymmetric Y-branches in integrated optical circuits will be of great interest in the near future. Experimental results are presented.

A study non-degenerate four-wave mixing in semiconductor optical amplifiers addresses the dynamical characteristics of conjugate optical pulses in such amplifiers. The scope of the experiment includes a detailed derivation of the coupled-wave mixing equations from which analytical solutions for the greatly simplified equations are also obtained. All of the characteristics that were observed are, to the researchers' knowledge, reported for the first time.

A study on free-space optical interconnects thoroughly investigated and demonstrated a novel technique for monolithically integrating bottom-emitting vertical-cavity lasers and bottom-illuminated resonant-cavity photodetectors. Part of the vertical cavity laser's bottom mirror was oxidized while the detector's bottom mirror was left as grown to achieve the required difference in bottom mirror reflectivities for both devices. Results are discussed.

A study on optoelectronic components working at mm-wave frequencies incorporated photonic device technologies with microwave monolithic integration techniques to derive optoelectronic microwave monolithic integrated circuits as a subset of optoelectronic integrated circuits. This general integration concept for producing ultrafast, InP-based optoelectronic microwave monolithic integrated circuits covered specific types of metal-semiconductor-metal photodetectors and specific types of InA1As-InGaAs high electron mobility transistors.

A hybrid implicit-explicit finite-difference time-domain (FDTD) method for solving the wave equation in nonlinear optical waveguiding structures is proposed. The new scheme combines the computational simplicity of the explicit scheme in linear medium regions with the superior stability property of the partially implicit scheme in regions of nonlinear materials, thus eliminating potential problems of instability associated with nonlinearity. Simulation results for Kerr-type nonlinear slab waveguides and corrugated waveguides are presented and compared with those obtained using the conventional noniterative FDTD scheme. Index Terms - Corrugated waveguides, FDTD methods, nonlinear wave propagation, optical Kerr effect, optical waveguides.

A study was conducted to analyze the design and optimization of high-speed resonant cavity enhanced Schottky photodiodes. The resonant microcavity was formed between the semitransparent Schottky contact and a low-loss distributed Bragg reflector. Quantum efficiency was optimized during the minimization of the front-surface reflectivity for incident light. In addition, a dielectric layer was utilized to reduce front-surface reflectivity.

A study was conducted to analyze the semiconductor multiple-quantum-well (MQW) acoustooptic modulator. The strain and electric-field parts produced by surface acoustic waves in a multilayered semiconductor piezoelectric structure were determined. The optical absorption coefficient spectra of the modulator was represented as a function of the power of surface acoustic waves. In addition, differences in the excitonic energies of the MQW resulting from strain were examined.

The development of a GaAs-InGaP triangular-barrier optoelectronic switch is presented. The device, grown via metalorganic chemical vapor deposition, exhibits a flexible optical function that is related to the potential barrier height that is controllable by incident light. S-shaped negative-differential-resistance performances are likewise manifested in the current-voltage characteristics because of hole confinement and avalanche multiplication in the operation of the device.

Research was conducted to investigate the gain saturation behavior of semiconductor traveling-wave optical amplifiers via a model that includes the specific dependence of gain on carrier concentration. The gain as a function of the carrier density was calculated using the Lutinger-Kohn Hamiltonian. Results indicate that a quantum well device operated in the flattened region of the gain-current curve will demonstrate the highest saturation power if designed with a tightly confining waveguide separate confinement heterostructure.

Research was conducted to examine the structural, electrical and ultrafast optical properties of furnace-annealed arsenic-ion-implanted GaAs for its applications in ultrafast optoelectronics. It was found that GaAs substrates implanted with 200-keV arsenic ions at 10 to the 16th power ions/cm2 and furnace-annealed at 500 degrees Cd-600 degrees C would have recovered its crystallinity, display picosecond photo-excited carrier lifetimes and be highly resistive.

Research was conducted to investigate some of the zero-dimensional physics controlling the performance of devices that could be made from self-assembled InAs-GaAs quantum dots. The strain distribution as well as the electronic spectra were studied via the valence force-field model and an eight-band k.p model, respectively. Results indicate that the effective mass approach for the conduction band provides significant errors and also suffers from the problem that there is no nonarbitrary choice for the effective mass.

A systematic study of the relative efficiency of realistic Bragg and metallic mirror systems for controlling the spontaneous emission of a localized dipolar emitter placed in the center of a planar semiconductor microcavity is presented. Theoretical results suggest that cavities bounded by metallic mirrors are likely to produce a very significant enhancement and inhibition of spontaneous emission while the semiconductor cavities bounded by Bragg mirrors display only a weak modification of spontaneous emission.

Quantum-well intermixing (QWI) using the impurity-free vacancy disordering (IFVD) technique is a simple and versatile method of controlling the bandgap of the QW after growth, especially in GaAs-A1GaAs structures. The IFVD effects in p-i-n and n-i-p GaAs-A1GaAs QS structures are examined, and it is demonstrated that a variation of the IFVD technique can be used in the control of bandgap energy.

The effects of optoelectronic feedback delay and the gain on the stability of an injection-locked laser were investigated. It was found that negative feedback configurations widen the injection locking domain of the laser and reduce its unstable region. On the other hand, in positive feedback configurations, laser diode generates a stable modulation with tunable multigigahertz frequency.

Quantum-cascade disk lasers with emission wavelengths of 9.5-microns and 11.5 microns were investigated. The threshold current density of disk lasers emitting at 9.5 microns was reduced below the value of the corresponding ridge waveguide geometry. The disk resonator was observed compatible with the quantum well laser active material. The effects of the microcavity regime were also cited.

Electrooptic sampling and heterodyne techniques were used to measure the optical frequency response of epitaxial lift-off 1.0 micron InP high-electron mobility transistors to 140 GHz. It was found that lift-off devices can be used at millimeter wave frequencies with no degradation response. The epitaxial lift-off process was cited of great potential in the integration of millimeter wave optoelectronic integrated systems.

The indirect band-to-band absorption coefficient and electrooptic effect in SiGe-Si quantum well optical modulators were computed. The effect of the quantum well shape and the dimensions on the optical properties of the optical modulator was also analyzed. The shift of the electron wavefunction created significant changes in the absorption coefficient, the refractive index, and the linear optic coefficient. These changes show that the novel amplitude and phase modulators can be realized in this material system.

A study was conducted of InP-InGaAs optoelectronic smart pixels for applications in optical interconnection and computing. The design, fabrication and performance of a high-sensitivity pixel and a high-bandwidth pixel were presented. The results indicate a minimum switching energy of 6 fJ, a maximum pixel bandwidth of 800 MHz and an optoelectronic gain of 3, the best overall performance characteristics of any optoelectronic smart pixel technology ever achieved.

A novel 3.5-GHz microwave counter using an opto-electronic harmonic heterodyne technique has been demonstrated. The system's performance has been discussed and evaluated, and is viewed as good, in comparison with today's microwave-counting systems. It is believed that this novel device has potential for measuring signals above 100 GHz.

Single-photon absorption coefficients in a two-photon autocorrelator waveguide were measured as a function of wavelength. A waveguide core was used to measure waveguide propagation loss. Scattering, leakage, and absorption mechanisms were considered during measurement. Photocurrent technique was used to measure band-to-band absorption. Single-photon absorption was suggested to occur through deep levels with long carrier lifetimes.

The optoelectronic properties of asymmetrically strained II-VI CdZnTe single-quantum-well (SQW) structures are analyzed. The structures are grown by molecular-beam epitaxy. Two mechanisms developed in III-V devices are combined to demonstrate low-temperature excitonic absorption modulation. Electron concentration in the SQW is controlled by a unique biasing scheme.

A theoretical model for determining the free-carrier optical gain and electronic band structures of wurtzite-strained quantum-well (QW) lasers is introduced. The model, which was demonstrated using a GaN-AlxGa(1-x)N QW structure, derives the optical gain coefficient from the spontaneous emission spectrum. The latter, in turn, is obtained from the effective-mass Hamiltonian, basis functions, valence band structures and interband momentum matrix elements.

The uncooled nonhermetic 1.3-micro meter InP-based communication lasers are as reliable as their hermetic counterparts in the loop/cable TV fiber applications but avoid the costs associated with hermetic packaging. The use of a proper dielectric facet passivation protects the laser from the ambient and maintains the proper facet reflectivity. Molecular beam deposition provides the desired passivation, and thermal degradation controls the reliability. These lasers are likely to bring about a revolution in low-cost optoelectronic packaging technologies.

An optimization technique for vertical-cavity surface-emitting lasers maximizes wall-plug efficiency by fixing the mirror reflectivity and varying the series resistance/parasitic leakage current. The method maximizes the power output through a suitable choice of threshold current multiplier as an operating point, and determines optimum reflectivity for both unstrained and strained quantum lasers. Temperature effects are also considered during the optimization, and the method provides simultaneous maximization of threshold current and efficiency in optoelectronic applications.

This paper reviews optically controlled wave propagation effects in coplanar transmission lines on semiconducting substrate. Special emphasis is laid upon distributed Schottky photodiodes where a depletion layer is formed below the center conductor. The cross section is that of a InAlAs/InGaAs/InP heterostructure, where the thin InGaAs layer is optimized with respect to optical absorption leading to an optical control of phase velocity, time delay or attenuation. Experimentally, phase shifts as high as 110 deg/mm at 9 GHz using an optical power of merely 50 ??? are obtained for an MBE grown sample with a suitable doping profile and for backside illumination through the tranparent InP-substrate. The theoretical treatment is based upon an equivalent circuit including the optoelectronic properties under different illumination conditions. It is further shown that periodic structures can successfully be used as efficient phase shifters or attenuators with optical control. This leads to interesting applications as optical MMIC's for microwave signal processing.

Optoelectronic mixers can exhibit a very wide bandwidth of operation with significantly reduced third-order intermodulation products. A 20-GHz bandwidth optoelectronic mixer has been constructed and characterized. The third order intermodulation terms were demonstrated to be more than 70 dB below the I.F. output. The mixer was then incorporated into a simple superheterodyne receiver architecture, which was shown to have a tangential sensitivity of -66 dBm and a compressive dynamic range of 44 dB. System limitations and possible improvements are discussed.

In this paper we present an analog winner-take-all MOS VLSI (metal-oxide semiconductor/very large scale integration) optoelectronic network. By varying either the input current or circuit parameters, the circuit can evidence several different behaviors such as contrast enhancement, strict winner-take-all, or winner-take-all with hysteresis. Simulation and experimental results from the prototype circuit are also discussed.

Analysis of the nonlinear operation of a dielectric distributed-feedback laser with complex coupling coefficient provides the relation of the small signal gain to the output power and the system parameters, including the spatial hole burning effect. It shows the varying contributions to laser operation above the threshold by the gain, loss and higher order Bragg gratings. A negative effect is possible in the partly gain-coupled structure above the threshold.

Analysis using a new method of almost periodic nonuniform, nonlinear distributed feedback (NLDFB) structures combines solutions of a strictly periodic, uniform NLDFB device with grating segmentation techniques. The method uses tapered, chirped, and phase shifted structures and NLDFB structures with an axially varying effective Kerr index. It gives new results about single and multiple-phase shifted NLDFB structures.

An analysis of spontaneous emission in the vicinity of a symmetric slab dielectric waveguide, using explicit energy-normalized functions for whole set of bound and radiating TE and TM modes, shows emission behavior as a function of the position of the radiating atom. The model analyzes the spontaneous emission-coupling efficiency to guided modes in planar erbium-doped amplifier structures.

Electrooptic amplitude/IM modulators of light in the form of circular polarizer-sample circular analyzer systems are analyzed. Principal characteristics and performance factors are examined with a linear electrooptic (EO) crystal as a sample and assuming nonideal components. Comparing results with linear polarizer-sample-linear analyzer systems, this method is better in EO-modulation sensitivity and more stable against misalignments.

Spontaneous optical and electrical oscillations occurring when the InP-InGaAsP lasing optoelectronic switch (LOES) is biased near the negative differential resistance region of the device characteristic is analyzed in theory and observed experimentally. These electrical oscillations result in current spikes up to 613 mA with a 0.6-microsecond FWHM in a device with a 7-V switching voltage and a 0.5-mA current. Repetition rate is found to be 900 Hz to 0.22 MHz, varying with bias current. Some LOES circuits have pulses correlated to current pulse.

A model of the Light Amplifying Optical Switch (LAOS) based on a derived expression for the nonlinear current gain of the heterojunction phototransistor (HPT) provides input-output characteristics, static I-V curve and switching voltage. Study of I-V characteristics and the switching mechanism show that nonlinear current gain of the HPT and the early effect creates thyristor-like characteristics in LAOS.

The characteristics of several laser-based optoelectronic devices are studied. Experiments are performed wherein the typical current-voltage properties of a double heterostructure optoelectronic switch (DOES) and a heterostructure field-effect transistor (HFET) are determined at various hoding voltage levels. Results indicate that the DOES and HFET devices are very useful for the design of smart pixels used in optical data processing.

The optical modulation and switching mechanisms of superlattice surface-normal asymmetric Fabry-Perot (SL-ASFP) reflection modulators are studied. The modulators' operating parameters, such as variations in the layer thickness, operating wavelength and temperature, are analyzed to determine their influence on the devices' performance. Results show that the SL-ASFP modulators have a very large on-off ratio, making them highly suitable for optical interconnection and photonic switching applications.

A new technology to advance optoelectronic integration is presented. It involves a class of optoelectronic devices with an inversion channel heterostructure containing one quantum-well active region. The inversion channel's geometry is such that it may be altered for the designing afield effect transistor, a current injection laser, a field effect modulator ora waveguide photodetector. A discussion on epitaxial growth and fabrication fordevice implementation is also provided.

A proposed method to define a large-signal digital switcher transistor based on a study of advances in optoelectronic systems is presented along with an electrooptic transducer terahertz-bandwidth electrical signal measurements. Optoelectronic methods are applied to derive high electron mobility transistor features and HFET small-signal frequency-domain properties from measurements of time-domain pulse-responses.

The design of a scalable, three-dimensional optoelectronic neural network utilizing the technology of free-space optical interconnects to surmount very-large-scale-integrated circuit communication problems is introduced. In the study, the neural and optical systems design along with the analog neuron and synapse circuits are presented. The neural system, which works on pulse-width-modulating optical neurons and pulse-amplitude-modulating electronic synapses, are also compared to a very-large-scale-integration counterpart.

Pulse shaping of optical pulses via programamble shaping is investigated in the study which used a 128-element liquid crystal modulator for the binary phase control of spatially distributed optical frequency components. Other pulse shaping processes for femtosecond pulses are also discussed, such as pulse position modulation, programmable pulse compression and modifiable cubic phase distortion.