The design and performance of a digital scanner based on ferroelectric liquid-crystal switchable wave plates and passive nematic liquid-crystal prisms are reported. The liquid-crystal prisms function as low-cost, integrable, lowangle birefringent prisms. A 1 x 64 scanner was built with -5.3 dB of average loss. By using an active filter, the limiting mispolarization cross talk of the scanner was reduced from -13 dB to less than -25 dB.
The design and experimental results of a new 2 x 2 optical routing switch based on liquid crystal is reported. The switch uses nematic liquid crystal for polarization beamsplitting and ferroelectric liquid crystal for polarization rotation. The polarization insensitive, broadcast capable, full duplex switch has a signal-to crosstalk ratio of ~20 dB, a switching speed below 250 micros and a measured insertion loss of 1.4 dB. We show that the basic 2 x 2 switch can be extended to form a N x N rearrangeable permutation network.
Dynamic global interconnections between processors in massively parallel computers are a highly desirable feature. Their implementation would greatly increase performance because large bandwidth interprocessor communication links may be reconfigured to match problem geometries. Global hardwiring of interconnects for large processor arrays is cumbersome, and present systems use rather tedious packet routing virtual interconnects. This report presents a novel design concept for a dynamic optical interconnect which would create a holographic interconnect between any two (or more) processors upon request. Each processor has a detector and a light source. A hologram may then be written into a nonlinear crystal which will diffract modulated light from a source at one processor to detectors at any other processors which desire that communication link. Writing is a two step process using a phase conjugate mirror and requiring the light sources of the involved processors to be mutually coherent. Preliminary analysis of this system along with an experimental proof of concept is discussed.
The experimental properties and a detailed model of a nematic liquid-crystal-tunable Fabry-Perot étalon with obliquely incident light are reported. As a single-wavelength switch, the étalon has an extinction ratio of 20.3 dB, an insertion loss of -1.7 dB, and a millisecond switching speed. As a filter, the étalon has a finesse of 15.1, a free spectral range of 20.4 nm, and a continuous tuning range of over 40 nm with less than 5 V.
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