Characteristics of temporal dynamics of liquid crystal spatial modulators as a performance limitation of tunable diffractive neural networks

Abstract

Liquid-crystal spatial light modulators are used in solving a broad range of contemporary problems in science and engineering. With the help of these modulators, it is possible to control the amplitude, phase, and direction of propagation of the coherent optical radiation in optical data-processing systems. However, the influences of the characteristics of time dynamics of liquid-crystal spatial light modulators on the performance of information optical systems, including diffraction neural networks, are studied quite poorly. We present the results of investigation of the time dynamics of phase modulation of an SLM-200 (Santec, Japan) liquid-crystal spatial light modulator. In our experiments, we used computer-synthesized binary phase-diffraction optical elements, and measured the characteristics of time dynamics of the optical modulator: 125 msec is the rise time of diffraction efficiency in the case of displaying of optical diffraction elements on the screen and 61.9 msec is the time of decay when switching the frames. For these characteristics, we can guarantee the formation of a variable optical field at a frame display frequency of 2 Hz with an interference level of—17.1 dB. As the frame display frequency increases, we observe the appearance of unavoidable interframe interferences, which, in turn, restrict the efficient performance of the information system. The obtained results can be used in the design of high-performance systems of optical data processing and diffraction neural networks.