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Abstract

Three special transducers for use with an experimental holographic recorder have been partly developed. They are a hologram page-composer with 50 ports, a solid-state digital light-deflector and a photodetector array for intercepting 100 light beams.

The page-composer is based on an electro-optic ceramic material, PLZT, in the form of a large slice placed between two matched arrays of lenses. This device produces 50 collimated digit-beams each of which can be modulated independently by external electronic switches. Generally, performance was good but some problems remain in the fabrication process and in the need to improve the dissipation of the heat generated in the PLZT.

The digital light-deflector comprises several stages of electro-optic crystals coupled with passive Wollaston prisms. A high transmission efficiency demands care to minimise internal surface reflections. The first large aperture stage, operating at the highest switching rate (1000000 transitions/sec) was difficult to design, and the deflector performance was limited by the lack of suitable high-voltage transistors for the electronic switches.

The development of a suitable photodetector array for operation at low light-levels was less of a problem. The design consists of a bundle of 100 monofilament light-guides attached to silicon photodiodes and followed by low-noise amplifiers.

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