Diffraction efficiency of MEMS based phase light modulator designed for visible spectrum used for infrared beam steering applications

Texas Instruments Phase Light Modulator (TI‑PLM) is an MEMS-based Spatial Light Modulator (SLM) initially designed for the visible spectrum. At near infrared (NIR), phase modulation depth inversely scales as wavelength increases. We quantify the NIR performance of a 0.67‑inch piston‑mode MEMS PLM and demonstrate practical adaptations for beam steering at 1550 nm. Two key steps enable improvements in power throughput: (1) replacing the VIS‑AR cover glass with an NIR‑AR window to suppress front‑window loss, and (2) tuning the mirror bias voltage to recover close to π phase modulation. Using staircase computer‑generated holograms (CGHs), we steer to eight azimuth angles (0°–315° in 45° steps) with diffraction angle of 2.74°. The NIR‑AR window raises 1550 nm transmission from 70% to 97%, increasing system optical throughput from ~20% to ~30%. Furthermore, tuning of the bias voltage yields ~ 0.97π phase modulation. With close to 0.97π phase modulation, the staircase CGH achieves about 56% first‑order diffraction efficiency (DE) and supports 50% overall optical efficiency. These results indicate a visible‑spectrum PLM can be an alternative yet efficient beam‑steering modality in NIR.