25-channel nematic liquid-crystal optical time-delay unitcharacterization

A 25-channel, 1-bit, free-space, nematic liquid crystal (NLCU) spatial light modulator (SLM)-based optical time delay unit (OTDU) is demonstrated with worst case electrical signal-to-noise ratios (SNR's) ranging from 50-60 dB for various delay/no-delay modes of operation and with a worst case -42,3-dB electrical channel isolation/crosstalk level. For comparison, single channel performance neglecting crosstalk noise but including within-channel leakage noise gives electrical SNR's from 74-85 dB, indicating that the leakage signal in this OTDU is minimal compared to crosstalk, To lower crosstalk, path-difference compensated imaging optics must be used by the OTDU