Characterization of the DuPont photopolymer for three-dimensional holographic storage

DuPont's HRF-150 photopolymer film is investigated for use in three-dimensional holographic memories. Measurements of sensitivity, hologram persistence, the lateral spread of the photoinitiated reaction, and the variation of diffraction efficiency with modulation depth, spatial frequency and tilt angle, and intensity are reported. We observed that the diffraction efficiency of the HRF-150 photopolymer for a given exposure decreases with increases in intensity and grating tilt angle. The holograms were nondestructively reconstructed for long periods of time at room temperature. The photoinitiated reaction spread less than 100 μm over a period of 16 h.     

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     

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.     

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.     

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.     

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.     

Polymer derived silicon oxycarbide ceramic monoliths: Microstructure development and associated materials properties

Polymer derived SiOC and SiCN ceramics (PDCs) are interesting candidates for additive manufacturing techniques to develop micro sized ceramics with the highest precision. PDCs are obtained by the pyrolysis of crosslinked polymer precursors at elevated temperatures. Within this work, we are investigating PDC SiOC ceramic monoliths synthesized from liquid polysiloxane precursor crosslinked with divinylbenzene for fabrication of conductive electromechanical devices. Microstructure of the final ceramics was found to be greatly influenced by the pyrolysis temperature. Crystallization in SiOC ceramics starts above 1200?°C due to the onset of carbothermal reduction leading to the formation of SiC and SiO₂ rich phases. Microstructural characterisation using ex-situ X-ray diffraction, FTIR, Raman spectra and microscopy imaging confirms the formation of nano crystalline SiC ceramics at 1400?°C. The electrical and mechanical properties of the ceramics are found to be significantly influenced by the phase separation with samples becoming more electrically conducting but with reduced strength at 1400?°C. A maximum electrical conductivity of 10¹ S?cm^?1 is observed for the 1400?°C samples due to enhancement in the ordering of the free carbon network. Mechanical testing using the ball on 3 balls (B3B) method revealed a characteristic flexural strength of 922?MPa for 1000?°C amorphous samples and at a higher pyrolysis temperature, materials become weaker with reduced strength.