Jean-Jacques P. Drolet

Compact, integrated dynamic holographic memory with refreshed holograms

An innovative architecture for compact, integrated volume holographic memories is described. It is based on phase-conjugate readout and on a modulator-detector-memory array implemented in a silicon integrated circuit. The lensless memory module sustains dynamic read-write holograms by periodic refreshing. The integrated circuit is described and experimentally characterized. Holograms were stored in a prototype storage module that uses a 30 degrees -cut BaTiO(3) crystal and the 90 degrees recording geometry. As many as three angularly multiplexed holograms were periodically refreshed and subjected to >40% decay from exposure to the reference beam over 50 to 100 cycles. Experimental data are presented.

Hybrid-Aligned Nematic Liquid-Crystal Modulators Fabricated on VLSI Circuits

A new method for fabricating analog light modulators on VLSI devices is described. The process is fully compatible with devices fabricated by commercial VLSI foundries, and the assembly of the modulator structures requires a small number of simple processing steps. The modulators are capable of analog amplitude or phase modulation and can operate at video rates and at low voltages (2.2 V). The modulation mechanism and the process yielding the modulator structures are described. Experimental data are presented.

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 /spl mu/m, 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.

Retardation and reduction of pulse distortion by group-velocity dispersion through pulse shaping

We show that a reduction in the pulse distortion caused by chromatic dispersion can be achieved through pulse shaping. We argue that a simple binary phase mask in the Fourier plane of the laser spectrum can improve the transmission of short pulses in a dispersive channel through reduced broadening. The argument was tested experimentally, and a good agreement was found with the theory.

Integrated optoelectronic interconnects using liquid-crystal-on-silicon VLSI

The various optical interconnection schemes that have been developed for the implementation of neural network architectures are reviewed. Volume holography in photorefra.ct.ive crystals is the most powerful interconnection method for this application. The use of liquid crystal smart pixel technology for the realization of the nonlinear activation function of the neurons is described. A novel method for combining liquid crystal devices and photorefractive holograms that leads to a very compact and versatile package, is presented.

Real-time binary phase-only circular harmonic filters using a liquid crystal television in the Fourier plane of an optical correlator

A rotation invariant optical correlator using a low-cost, liquid crystal television (LCTV) in the Fourier plane is described. The performance of the LCTV used as a filter support medium is evaluated, using interferometric measurements and an image reconstruction experiment. Different operating modes of an LCTV suitable for encoding binary phase-only filters are discussed. Finally, a modified LCTV is used in the filter plane of a conventional 4-f correlator to encode unipolar binary phase-only matched filters and unipolar binary phase-only circular harmonic filters. Optical experimental results are compared with the results of computer experiments.

Compact Holographic Memory Module

Publisher Summary Holographic memory has received attention in recent years as a technology that can provide a large storage density with high speed. This chapter examines the current state of holographic compact memory module systems and addresses the primary challenges that this technology faces: size, speed, and cost. A fast holographic random access memory (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. The analysis shows that for the HRAM to become competitive, the principal task is to reduce spatial light modulator (SLM) 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.

Compact holographic memory implemented with photorefractive crystals

We have designed and implemented a compact holographic memory module that uses a dual spatial-light modulator/detector optoelectronic integrated circuit in the lens-less phase- conjugate geometry. In this paper we discuss optical design and systems issues and present recent experimental results.

Modular Integrated Dynamic Holographic Memory With Refreshed Holograms

An innovative architecture for compact, integrated volume holographic memories is described. It is based on phase-conjugate readout and on a modulator–detector–memory array implemented in a silicon integrated circuit. The lensless memory module sustains dynamic read–write holograms by periodic refreshing. The integrated circuit is described and experimentally characterized. Holograms were stored in a prototype storage module that uses a 30 degree-cut BaTiO3 crystal and the 90± recording geometry. As many as three angularly multiplexed holograms were periodically refreshed and subjected to .40% decay from exposure to the reference beam over 50 to 100 cycles. Experimental data are presented.

Liquid crystal displays using the hybrid alignment method

We describe a new approach for the fabrication of highly integrated low-cost displays based on liquid crystal on silicon technology. The method employs a liquid crystal modulator structure built directly on top of a VLSI die and is suitable to both head-mounted and projection displays.