2 October 2008 Continuous laser beam steering with micro-optical arrays: experimental results
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High resolution inertialess beam steering systems are required for numerous applications, including laser radar, multitarget designation or active imaging. We present a 1.55μm operating continuous laser beam steering system based on the cascading of an electro-optic PMN-PT ceramic optical phased array (OPA) and of two piezoactuated microlenses arrays (MLA). The function of the single devices and the principle and the operation of the combination of both are explained. Then we describe the experimental setup which was realized and outline the test results. The MLA large angle scanner consists of two MLAs, one of which can be moved with respect to the other by piezodrivers. This setup acts as a blazed grating and thus results in a discrete beam steering. Each steering position corresponds to a multiple of 2pi phase shift between adjacent beamlets. In order to get a continuous steering, we combined the MLA scanner with an electro-optic ceramic OPA. The OPA generates the piston distribution that compensates the phase difference between adjacent beamlets of the MLAs and reconstructs a continuous wavefront. The PMN-PT OPA consists in 64 phase modulators with 210µm period and a 0.5 fill factor. The maximum required voltage corresponding to the 2π phase shift is 150 Volts at 1.55µm. The OPA is imaged on the 105μm period MLAs with a 0.5-magnification telescope. The two MLAs are in a Keplerian telescope with field lenses arrangement. The steering performances of the MLAs alone are +/-12° scan angle with 28 discrete positions. Using the combined architecture, we were able to resolve 64 angular directions between each of these 28 positions. We thus experimentally obtained a continuous steering at 1.55μm over +/-12° with an angular resolution of 0.24mrad, i.e. 1800 resolved directions, with only 64+1 control voltages.
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J. Bourderionnet, J. Bourderionnet, M. Rungenhagen, M. Rungenhagen, D. Dolfi, D. Dolfi, H. D. Tholl, H. D. Tholl, "Continuous laser beam steering with micro-optical arrays: experimental results", Proc. SPIE 7113, Electro-Optical and Infrared Systems: Technology and Applications V, 71130Z (2 October 2008); doi: 10.1117/12.800120; https://doi.org/10.1117/12.800120

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