Multiple quantum wells spatial light modulators for correlation based processors

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To be competitive with their electronic counterparts, correlation-based optical processors require very fast spatial light modulators (SLMs) that can perform simultaneously phase and amplitude modulation. Owing to their ultra-high speed, multiple quantum well (MQW) SLMs have been early identified as very good candidates. However, the coding domain of MQW SLMs is not widely known. We present here a study of available coding domains of MQW SLMs. We demonstrate that pure amplitude modulation, ternary { -1, 0, + 1} modulation and quaternary {0, + 1, e^i2π/3, e^i4π/3}, modulation are examples of coding domains that can be achieved by tuning a few parameters in the design of Fabry-Perot MQW modulators. We show that ternary and quaternary filters provide much better results than binary filters for the recognition of objects embedded in highly cluttered noise. Finally, we present a technique, the time-averaged pseudo-random encoding technique, which enables encoding of any complex filter onto a quaternary modulator. Combined with the time-­averaged pseudo-random encoding technique, MQW SLMs may pave the way to the development of new optoelectronic correlator systems with improved speed and accuracy performance.