Fast Multi-Spectral Liquid-Crystal-On Silicon Spatial Light Modulators (Preprint)

摘要

The stressed liquid-crystal (SLC) electro-optic effect promises fast electro-optic response times even for design wave-lengths in the infrared (IR). Here we report characteristics of SLC devices appropriate for use as liquid- crystal-on-silicon (LCOS) spatial light modulators (SLMs) in the near-IR band (lambda = 1.8 to 2.5 mum), mid-IR band (3 to 5.5 mum) and far-IR band (8 to 14 mum). For these three bands, we fabricated SLC devices with 5, 10, and 20 mum thicknesses; at drive voltages of 25, 50, and 125 V, respectively, these devices gave half-wave modulation with response speeds in the 1.3 to 1.6 ms range. Visible-light measurements on a 20-mum-thick SLC device between crossed polarizers gave a contrast ratio of 360:1 which improved to nearly 18,000:1 with a Babinet-Soleil compensator offsetting residual SLC retardance. The drive voltages for near-IR and mid-IR devices enable fabrication of SLCOS devices using high-voltage transistors options in standard CMOS processes; improvement of SLC materials by modest increase of birefringence delta n and dielectric anisotropy delta e would further bring far-IR devices within the standard CMOS drive voltage range. High-voltage CMOS transistor design rules permit pixel pitches less than 24 mum, making 1000 x 1000 SLMs feasible.