Fig. 1. Conceptual design (as shown on the left) and principle (as shown on the right) of transmissive and reflective-type LCOPAs. (a) Transmissive LCOPA developed by Raython in 1991^[1]; (b) reflective LCOPA developed by Raython in 1994^[23]

Fig. 2. 1D reflective LCOPA developed by BNS. (a) Photo of 1D reflective LCOPA device (1 pixel×4096 pixel) and its experiment results for beam steering at the wavelength of 1550 nm^[19]; (b) photo of 1D reflective LCOPA device head(1 pixel×12288 pixel) ^[24]

Fig. 3. 1D transmissive and reflective dual-frequency LCOPA devices developed by Rockwell. (a) Core element and (b) appearance of the test device of reflective dual-frequency LCOPA device^[4]; (c) core element, (d) appearance of the test device and (e) structural diagram of transmissive dual-frequency LCOPA device^[25]

Fig. 4. Demonstration experiment, principle and structure of the 1D LCOPA device developed by Vescent Photonics^[26]_. (a) Demonstration experiment; (b) principle and structure

Fig. 5. Deflection effect diagrams of LCOPA. (a) deflection effect diagrams of liquid crystal optical phased array developed by Harbin Institute of Technology^{[17, 19]}; (b) Deflection effect diagrams of LCOPA developed by the University of Electronic Science and Technology, left for 635 nm of the incident beam, right for 1060 nm of the incident beam^[33]

Fig. 6. Diffraction efficiency improvement by four optimization approaches^[48]

Fig. 7. Principal block diagram and demonstration experimental block diagram of indoor point-to-two point wireless optical communication using liquid crystal double beam deflection^[20]. (a) Principal block diagram; (b) demonstration experimental block diagram

Fig. 8. Schematic diagram of cascade structure adopted by University of Electronic Science and Technology of China^[66]

Fig. 9. High power LCOPA^{developed by Raytheon [68]}