Liquid crystal spatial light modulators (LC-SLMs) are usually polarization sensitive optical elements. In this paper, we propose a polarization-independent beam steering system to overcome the polarization problem of conventional liquid crystal devices by employing two polarization-dependent LC-SLMs, a polarizing beam splitter and a half-wave plate. In this system, two one-dimensional LC-SLMs are aligned orthogonally to deflect the beam in azimuthal and elevation, respectively. This system enables LC-SLMs to work in any polarization state of incident light, and can realize continuous two-dimensional laser beam pointing. Properties of polarization-independence as well as two-dimensional beam steering were mathematically and experimentally verified with a good agreement. Using the well aligned beam steering system, linearly polarized beams in different polarization angle are deflected with high accuracy and efficiency. The measured angular deviations are less than 5 micro-radians to show a high-accuracy beam steering of the system. This polarization-independent beam steering scheme is useful in the applications of nonmechanical laser communication, Lidar, and other LC-based devices.
This paper reviews the research progress of liquid crystal optical phased array (LCOPA) devices in space laser communication applications. According to the constraints of space applications and system requirements, in the design and key technologies of array devices, the research progresses on the implementation methods such as wide-point range, large-aperture optical aperture, short response time, and space environment adaptability are emphatically introduced. In introducing the wide beam pointing range, the beam control method and the digital concatenation scheme are mainly described. In the study of large aperture, the area filling module and the area selection module are separately analyzed. And comparatively expounded the realization of sub-millisecond order rapid response of liquid crystal materials, and finally gave the United States Air Force laboratory's research on the liquid crystal optical phased array device irradiation environment adaptability research results.
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