Abstract
We present a high-speed optical beamsteering system based on an 8x8 MEMS phased array. The system incorporates an in situ interferometer that provides a real-time, dynamic measure of the phase of each mirror in the array during beamsteering. A closed-loop phase-control algorithm results in <π/100 mirror phase accuracy and far field beam steering is shown. Stroboscopic measurement capabilities are demonstrated which allow us to show feedforward control to eliminate micromirror ringing.
Highlights
Optical phased arrays have been shown as viable options for beamsteering [1,2,3]
We present a high-speed optical beamsteering system based on an 8x8 MEMS phased array
The ability to measure the dynamic response allows us to show the elimination of the harmonic motion using feedforward waveform shaping
Summary
Optical phased arrays have been shown as viable options for beamsteering [1,2,3]. Phased array elements need only create phase delays within a wavelength due to the periodic nature of the light. The system incorporates an in situ interferometer that provides a real-time, dynamic measure of the phase of each mirror in the array during beamsteering This holds advantages over capacitive sensing which is subject to parasitic capacitance from external instruments and requires large structures (e.g. comb drives) to achieve nanometer resolution [6, 7]. We perform 4f image relaying with a pair of matched 10 cm focal length lenses to achieve 7.5 μm imaging resolution; sufficient to distinguish individual mirrors in the MEMS array This image relaying system is necessary to keep the magnification microscope objective away from the sample and allow for steered output. The speed of one iterative loop is limited by the long (~0.1 second) response time of the phase shifter required for PSI This speed is sufficient for initially setting and periodically updating the look-up table for initial device calibration and correction for long term drift
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