Masayasu Yamaguchi

Free-space optical interconnections with liquid-crystal microprism arrays

Liquid-crystal microprism arrays are shown to be useful for providing electrically controlled alignment of optical beams and fixed various free-space optical interconnections. They can deflect closely spaced micro-optical beams individually to any position with high transmittance (95%), high deflection angle (~10°), and low voltage (<2.8 V(rms)). Various fixed optical interconnections can be made simply by changes in the voltages applied to the microprism.

Experiments on a multichannel holographic optical switch with the use of a liquid-crystal display

A new configuration of holographic switches is proposed and verified for multichannel optical switching. Experimental 1 x 64 and 2 x 32 switching is achieved by using real-time binary phase-only holograms generated by a twisted nematic liquid-crystal display. This holographic free-space switching is applicable to photonic switching systems and optical interconnections.

4 × 4 free-space optical switching using real-time binary phase-only holograms generated by a liquid-crystal display

Experimental 4 × 4 free-space optical switching is successfully demonstrated by real-time binary phase-only holograms. The real-time holograms are generated by a twisted nematic liquid-crystal display, which is a binary phase-only modulator. This holographic free-space switching is applicable to optical interconnections and photonic switching systems.

High-density digital free-space photonic-switching fabrics using exciton absorption reflection-switch (EARS) arrays and microbeam optical interconnections

We describe a compact digital free-space photonic-switching module that uses microbeam optical interconnections based on stacked planar optics and exciton absorption reflection-switch (EARS) arrays. Microbeam optical interconnections become increasingly attractive as the number of optical input and output (I/O) ports increases because of their small size. The EARS device provides the digital-signal regeneration needed for constructing a multistage switching network. This paper mainly describes the experimental investigation of a prototype switch having a two-stage, 16-input, 16-output structure (four sets of 4/spl times/4 switches), with highly dense two-dimensional fiber array pigtails acting as high-density optical I/Os. The prototype is approximately 30/spl times/90/spl times/22 mm [60 cc]. A relay lens array inserted between stages eliminates the beam spreading caused by diffraction, which decreases the required positioning accuracy for the optomechanical packaging. Two-stage switching at a data transmission rate of 4 Mb/s has been demonstrated. Increasing the operating speed of the switch and introducing an easy assembly method to reduce assembly costs are future enhancements.

VARIABLE OPTICAL DELAY LINE BASED ON A BIREFRINGENT PLANAR OPTICAL PLATFORM

A variable optical delay line is proposed for accurately adjusting optical signal timing in photonic systems. This delay line is based on a birefringent planar optical platform characterized by the multiple reflection of light beams. It consists of a birefringent plate, lambda/4 plates, mirrors, and a liquid-crystal layer. It can select an arbitrary delay from a set of discrete delays precisely determined by the thickness of the birefringent plate. A feasibility study confirms seven-step delay line operation with a 240-ps unit delay.

Estimation of the possible scale for holographic switches with liquid-crystal displays

Simulating the positions of output beams under the assumption that a liquid-crystal display acts as a binary phase modulator reveals that the number of the outputs increases almost linearly with the square root of the number of pixels assigned to an input. This result is confirmed by experiments, and it is estimated that 1016 outputs can be obtained when the number of pixels is 700 × 700. Holographic switches with liquid-crystal displays are therefore suitable for large-scale switches.

Liquid-Crystal-Based Optoelectronic Hybrid Structure for Optical Parallel Processing Devices

An easy-to-handle optical device structure is proposed for optical parallel processing devices. This is an opto-electronic hybrid structure consisting of liquid crystal polarization controllers and polarizing beam splitters. Experimental memory and AND cells based on this structure are successfully demonstrated.