Abstract
Optical-phased arrays (OPAs) enable complex beamforming, random-access beam pointing, and simultaneous scan and tracking of multiple targets by controlling the phases of two-dimensional (2D) coherent emitters. So far, no OPA can achieve all desirable features including large 2D arrays, high optical efficiency, wideband operation in wavelengths, fast response time, and large steering angles at the same time. Here, we report on a large-scale 2D OPA with novel microelectro-mechanical-system (MEMS)-actuated phase shifters. Wavelength-independent phase shifts are realized by physically moving a grating element in the lateral direction. The OPA has 160×160 independent phase shifters across an aperture of 3.1 mm×3.2 mm. It has a measured beam divergence of 0.042°×0.031°, a field of view (FOV) of 6.6°×4.4°, and a response time of 5.7 μs. It is capable of providing about 25,600 rapidly steerable spots within its FOV. The grating phase shifters are optimized for the near-infrared telecom wavelength bands from 1200 to 1700 nm with 85% optical efficiency.
Highlights
Optical-phased arrays (OPAs) enable electronic steering of optical beams
The phase of the reflected wave experiences a 2π phase shift when the mirror is displaced by half a wavelength [21]. 2D MEMS OPAs have been reported for UV [22,23] and near-infrared wavelengths [24,25,26,27]
We report on a large-scale 2D OPA with novel MEMS-actuated grating phase shifters
Summary
By customizing the optical phases of individual emitters in a two-dimensional (2D) array, versatile beamforming functions such as random-access beam pointing, independent scanning of multiple beams, and simultaneous scanning and tracking of targets can be realized, similar to the phased-array radars or synthetic apertures in the microwave regime They are compact, robust, agile, and can be scaled to large apertures for longer reach. By moving a grating element laterally, the optical phase of the diffracted beam is shifted in proportion to the displacement [29] Unlike piston mirrors, this phase shift is independent of wavelength, which enables broadband applications without loss of efficiency. High optical efficiency, and large field-of-view were achieved by stacking fine-pitched grating phase shifters on top of MEMS actuators. A detailed comparison of our work and reported OPAs is summarized in Table S1 of Supplement 1
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