Large arrays of spatial light modulators hybridized to silicon integrated circuits

Wide spectral bandwidth electro-absorption modulator using coupled micro-cavity with asymmetric tandem quantum well

For reliable three dimensional (3D) imaging system, it is necessary for the optical shutter to have a wide spectral bandwidth operation and enhanced modulation depth. We propose an electro-absorption modulator (EAM) based on coupled Fabry-Perot cavities with micro-cavity (CCMC) which uses asymmetric tandem quantum wells (ATQWs) to obtain improved spectral bandwidth and enhanced modulation depth. Several modulator designs are investigated to obtain improved modulation performance such as wider spectral bandwidth and enhanced modulation depth. It was found that among all the studied modulator geometries, CCMC structure with ATQWs provides the widest spectral bandwidth of 9.6nm and high modulation depth in excess of 50% at -24V, which is good agreement with theoretical calculations. These results suggest that EAM has excellent potential as optical shutter for 3D imaging application.

Large aperture asymmetric Fabry Perot modulator based on asymmetric tandem quantum well for low voltage operation

Large aperture image modulators used as demodulator in receiver path are an important component for the use in three dimensional (3D) image sensing. For practical applications, low voltage operation and high modulation performance are the key requirements for modulators. Here, we propose an asymmetric Fabry-Perot modulator (AFPM) with asymmetric tandem quantum wells (ATQWs) for 3D image sensing. By using ATQWs for the AFPM design, the device operated at -4.25V, and the operating voltage was significantly lower by about 23% compared to -5.5V of a conventional AFPM with 8nm thick multiple QW with a single QW thickness (SQWs), while achieving high reflectivity modulation in excess of 50%. The performance of the fabricated devices is in good agreement with theoretical calculations. The pixelated device shows a high modulation speed of 21.8 MHz over a large aperture and good uniformity. These results show that AFPM with ATQWs is a good candidate as an optical image modulator for 3D image sensing applications.

GaAs-based multiple-quantum-well spatial light modulators fabricated by a wafer-scale process

The design, fabrication, and characterization of large, two-dimensional multiple-quantum-well modulator arrays are presented. Such arrays present a speed advantage compared with competing technologies such as liquid crystals and micromirrors, which are intrinsically limited to the kilohertz range. We discuss the design compromises to reach high-contrast, low-voltage swing optical structures compatible with complementary metal-oxide semiconductor-based integrated circuits and present experimental results. Contrast ratio of 5:1 (limited by the fill factor), variations in uniformity below 1nm, and frame rates in excess of 10kHz are demonstrated. Technology maturity for volume production is also discussed.

Optoelectronic implementation of a 256-channel sonar adaptive-array processor

We present an optoelectronic implementation of an adaptive-array processor that is capable of performing beam forming and jammer nulling in signals of wide fractional bandwidth that are detected by an array of arbitrary topology. The optical system makes use of a two-dimensional scrolling spatial light modulator to represent an array of input signals in 256 tapped delay lines, two acousto-optic modulators for modulating the feedback error signal, and a photorefractive crystal for representing the adaptive weights as holographic gratings. Gradient-descent learning is used to dynamically adapt the holographic weights to optimally form multiple beams and to null out multiple interference sources, either in the near field or in the far field. Space-integration followed by differential heterodyne detection is used for generating the system's output. The processor is analyzed to show the effects of exponential weight decay on the optimum solution and on the convergence conditions. Several experimental results are presented that validate the system's capacity for broadband beam forming and jammer nulling for linear and circular arrays.

Dependence of the Contrast Ratio on Crystal Thickness in an Electroabsorptive Spatial Light Modulator That Uses GaAs

The contrast ratio of an optically addressed spatial light modulator that uses electroabsorption in a GaAs single crystal is discussed experimentally and theoretically. The modulator has the same structure as a Pockels readout optical modulator. The contrast ratio depends strongly on the change in the absorption coefficient and on the thickness of the GaAs crystal. From the experimental results and from theoretical investigations of the Franz-Keldysh effect, the change in the absorption coefficient is estimated by use of the quadratic equation of an applied electric field that is not excessively strong. Under this condition, an optimum thickness of the GaAs crystal plate that will yield the maximum contrast ratio can be determined.

High-Contrast Spatial Light Modulator by use of the Electroabsorption and the Electro-Optic Effects in a GaAs Single Crystal

A new spatial light modulator that uses the electroabsorption and the electro-optic effects in a GaAs single crystal is proposed. The device has the same structure as a Pockels readout optical modulator and can be operated at a frame rate higher than 500 Hz. When the electroabsorption and the electro-optic effects are combined, the dynamic range (contrast ratio) becomes larger than that which results when either effect is used singly. It was experimentally confirmed that the modulator has a high contrast ratio (greater than 2000:1), high sensitivity, and consequently large gamma characteristics.

High-Speed and High-Contrast Spatial Light Modulator that Uses Electroabsorption in a GaAs Single Crystal

A new spatial light modulator that uses electroabsorption induced by the Franz-Keldysh effect in a GaAs single crystal is proposed. The device has the same structure as the Pockels readout optical modulator, is driven by a high ac voltage, and is operated in the superprime mode. Its high-frame-rate (over 500-Hz) operation, high contrast ratio (350:1), and large gamma characteristics (2.47) were experimentally confirmed in the transmission mode, although its operating-wavelength (readout) region is restricted to a narrow band near the band gap. In the reflection mode, however, this device has a high contrast ratio and large gamma characteristic (approximately 5), offering the possibility of its use as a nonlinear device.

WARRP Core: Optoelectronic Implementation of Network-Router Deadlock-Handling Mechanisms

The wormhole adaptive recovery-based routing via pre-emption(WARRP) core optoelectronic chip, which integrates coredeadlock-handling circuitry for a fully adaptive deadlock-freemultiprocessor network router, is presented. This chip demonstratesprimarily the integration of complex deadlock-recovery circuitry andfree-space optoelectronic input-output on a monolithicGaAs-based chip. The design and implementation of thefirst-generation, bit-serial, torus-connected chip that uses 1400transistors and six light-emitting diode-photodetector pairs is presented.

Analysis of the confined-reference coherence-encoding method for image transmission through optical fibers

Performance of the confined-reference coherence-encoding method for two- and three-dimensional complex image-data transmission through optical fibers is analyzed. Both acousto-optic and phase-only spatial light modulator implementations are considered. The signal-to-noise ratio, data rate, and probability of bit errors are issues that are discussed. Simulation results are presented.

Toward an optimal foundation architecture for optoelectronic computing. Part I. Regularly interconnected device planes

By systematically examining the tree of possibilities for optoelectronic computing architectures and offering arguments that allow one to prune suboptimal branches of this tree, I come to the conclusion that electronic circuit planes interconnected optically according to regular connection patterns represent an alternative that is reasonably close to the best possible, as defined by physical limitations. Thus I propose that this foundation architecture should provide a basis for future research and development in this area.