Holographic random access memory (HRAM)

We examine the present state of holographic random access memory (HRAM) systems and address the primary challenges that face this technology, specifically size, speed, and cost. We show that a fast HRAM system can be implemented with a compact architecture by incorporating conjugate readout, a smart-pixel array, and a linear array of laser diodes. Preliminary experimental results support the feasibility of this architecture. Our analysis shows that in order for the HRAM to become competitive, the principal tasks will be to reduce spatial light modulator (SLM) and detector pixel sizes to 1 μm, increase the output power of compact visible-wavelength lasers to several hundred milliwatts, and develop ways to raise the sensitivity of holographic media to the order of 1 cm/J     

Monolithic optoelectronic circuit design and fabrication byepitaxial growth on commercial VLSI GaAs MESFET's

A technique for realizing large-scale monolithic OEIC's, which involves epitaxially growing GaAs-based heterostructures on fully metallized commercial VLSI GaAs MESFET integrated circuits, has recently been reported. In the initial work the circuits and LED's occupied distinct halves of a chip, the dielectric growth window was wet-etched after circuit fabrication, and the LED's required both n and p ohmic contacts to be formed after epitaxial growth. In this letter we report the use of standard foundry process etches to open dielectric growth windows intermixed with circuitry and the growth of n-side-down LED's on a source/drain ion-implanted n⁺ region serving as the n ohmic contact. A winner-take-all neural circuit is demonstrated using these advances, which are important steps toward realizing higher levels of circuit integration     

Chemical separations by bubble-assisted interphase mass-transfer

We show that when a small amount of heat is added close to a liquid-vapor interface of a captive gas bubble in a microchannel, interphase mass-transfer through the bubble can occur in a controlled manner with only a slight change in the temperature of the fluid. We demonstrate that this method, which we refer to as bubble-assisted interphase mass-transfer (BAIM), can be applied to interphase chemical separations, e.g., simple distillation, without the need for high temperatures, vacuum, or active cooling. Although any source of localized heating could be used, we illustrate BAIM with an all-optical technique that makes use of the plasmon resonance in an array of nanoscale metal structures that are incorporated into the channel to produce localized heating of the fluid when illuminated by a stationary low-power laser.     

High-density recording in photopolymer-based holographic three-dimensional disks

The performance specifications of a holographic three-dimensional disk system are experimentally characterized. A surface density of 10 bits/μm(2) is experimentally demonstrated with a 100-μm-thick photopolymer as the recording medium.     

Shift multiplexing with spherical reference waves

Shift multiplexing is a holographic storage method particularly suitable for the implementation of holographic disks. We characterize the performance of shift-multiplexed memories by using a spherical wave as the reference beam. We derive the shift selectivity, the cross talk, the exposure schedule, and the storage density of the method. We give experimental results to verify the theoretical predictions.     

Monolithic integration of SEEDs and VLSI GaAs circuits by epitaxy on electronics

Using the epitaxy-on-electronics (EoE) process, self-electrooptic effect devices (SEEDs) have been monolithically integrated with VLSI GaAs electronics. The EoE approach provides both depletion-mode and enhancement-mode MESFETs for large-scale, high-density optoelectronic circuits. The performance of SEEDs grown by molecular beam epitaxy at a reduced temperature compatible with the EoE process is shown to be robust, and modulators with contrast ratios of 2.3:1 at 7.5-V bias have been integrated on commercially processed VLSI GaAs circuits. The EoE-SEED process offers potential improvements over the FET-SEED process, facilitating the applications of SEEDs in free-space optical switching and computing.     

Three-dimensional holographic disks

We describe optical disks that store data holographically in three dimensions by using either angle multiplexing or wavelength multiplexing. Data are stored and retrieved in parallel blocks or pages, and each page consists of approximately 10(6) bits. The storage capacity of such disks is derived as a function of disk thickness, pixel size, page size, and scanning parameters. The optimum storage density is approximately 120 bits/μm(2).     

Liquid-crystal blazed-grating beam deflector

A transmission-type nonmechanical multiple-angle beam-steering device that uses liquid-crystal blazed grating has been developed. Sixteen steering angles with a contrast ratio of 18 has been demonstrated. A detailed analysis of the liquid-crystal and poly(methyl methacrylate) blazed-grating deflector was carried out to provide guidance during the deflector's development. A manufacturing offset compensation technique is proposed to improve the device's performance greatly. A hybrid approach utilizing electrically generated blazed grating combined with the cascading approach described here yields in excess of 500 deflecting angles.     

High-responsivity optical FET's fabricated on a FET-SEED structure

Optical detectors with responsivity of 1000 A/W and response time of 10 μs at 50 nW optical input power were fabricated using the AT&T FET-SEED process