Fast Multi-Spectral Liquid-Crystal-On Silicon Spatial Light Modulators (Preprint)
DISPLAYTECH INC LONGMONT CO
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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 3601 which improved to nearly 18,0001 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.
- Physical Chemistry