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19 February 2014 High-contrast grating MEMS optical phase-shifters for two-dimensional free-space beam steering
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Proceedings Volume 8995, High Contrast Metastructures III; 89950Q (2014) https://doi.org/10.1117/12.2045341
Event: SPIE OPTO, 2014, San Francisco, California, United States
Abstract
We report an optical phased array (OPA) for two-dimensional free-space beam steering. The array is composed of tunable MEMS all-pass filters (APFs) based on polysilicon high contrast grating (HCG) mirrors. The cavity length of each APF is voltage controlled via an electrostatically-actuated HCG top mirror and a fixed DBR bottom mirror. The HCG mirrors are composed of only a single layer of polysilicon, achieving >99% reflectivity through the use of a subwavelength grating patterned into the polysilicon surface. Conventional metal-coated MEMS mirrors must be thick (1-50 μm) to prevent warpage arising from thermal and residual stress. The single material construction used here results in a high degree of flatness even in a thin 350 nm HCG mirror. Relative to beamsteering systems based on a single rotating MEMS mirror, which are typically limited to bandwidths below 50 kHz, the MEMS OPA described here has the advantage of greatly reduced mass and therefore achieves a bandwidth over 500 kHz. The APF structure affords large (~2π) phase shift at a small displacement (< 50 nm), an order-of-magnitude smaller than the displacement required in a single-mirror phase-shifter design. Precise control of each all-pass-filter is achieved through an interferometric phase measurement system, and beam steering is demonstrated using binary phase patterns.
© (2014) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Mischa Megens, Byung-Wook Yoo, Trevor Chan, Weijian Yang, Tianbo Sun, Connie J. Chang-Hasnain, Ming C. Wu, and David A. Horsley "High-contrast grating MEMS optical phase-shifters for two-dimensional free-space beam steering", Proc. SPIE 8995, High Contrast Metastructures III, 89950Q (19 February 2014); https://doi.org/10.1117/12.2045341
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