Die-warp compensation of a visible-pixel MEMS phase light modulator for beam steering at 1550nm

Abstract

Wavefront quality often dominates throughput of device such as optical cross-connect switch and free-space optical communication. MEMS SLM enables flexible beam routing and steering, however it is known that the deformation of MEMS backbone. Or warp of the die introduces wave aberration due to the reflective nature of the MEMS-SLM. To correct for the aberration induced by die warp, we investigate optical compensation of the aberration by binary computer-generated hologram (CGH) for a visible-pixel MEMS phase light modulator operated at 1550 nm. A Littrow interferometry at 632.8 nm measures the spatial phase error, which is encoded through local displacement of linear CGH profile uopon beam steering. Correction performance is evaluated by point spread functions (PSF) of steered beam with CGH having grating periods of 2, 5, 10, and 15 pixels. After correction, the PSF exhibits close to diffraction limited performance as the central-lobe extent is approximately 9 × 16 camera pixels, compared with a theoretical reference of 7.2 × 14.3 pixels.