Researchoncoherent Beam Combination Based On Multiple Liquid Crystal Phased Arrays

As the result of combination between laser technique and microwaves detecting technology, laser radar is an advanced detection method. Liquid Crystal Phased Array(LCPA) is an Optical ptical Phased Array whose phase-shift unit is made of liquid crastal, it’s able to provide laser radar with steady beam pointing and accurate scanning., and it is often used as the scanner of laser radar. However, the capacity to enhance the power of single laser is limited because of heating effects inside lasers, which causes the restricted scope of laser radar. In the article the combination of beam steering based on LCPA and Coherent Beam Combination(CBC) is researched. Relying on this technology, multiple coherent beams are controlled byan array consisting of LCOPAs, so that CBC can be realized in arbitrary position or direction. Synthesized laser beam of CBC has several advantages, such as high power, high resolution and high beam quality. Depending on technology of CBC based on multiple LCPAs, transmitting power of laser radar can be improved, and sensitive beam steering capacity of LCPA can be kept as well. With the aid of encoded voltage, space scanning in certain area can be realized.Content of this paper is relied on a specific research project. Main work of research on CBC based on multiple LCPAs is shown below:1. Principle of beam steering based on LCPA is stated. Electro-optic effect of liquid crystal material is presented, phase shifting theory of LCPA is analyzed, and the mathematical model of beam steering by LCPA is created, then the result of beam steering is verified through computer simulation.2. Theoretical model of CBC based on LCPAs is established. Diffraction theory and CBC theory are stated, besides beam steering principle based on LCPA is studied. Thentheory of CBC based on multiple LCPAs is put forward. Depending on research results above mathematical model of CBC is established. Two CBC patterns are proposed, including parallel pattern and focused pattern.3. Performance of CBC based on multiple LCPAs is analyzed. Several evaluation parameters are put forward based on requirements in application environment. Analysis are mainly launched from three aspects.First, the cause of pointing error is determined and the solution is put forward. Second, distribution of peak intensity inside target area is determined. Third, Beam quality of synthesized beam is analyzed through defined parameter.4. Optimization algorithms of CBC based on multiple LCPAs are researched. As the transmission directions of coherent beams are the same in parallel type CBC. SPGD algorithm is used to promote the efficiency of CBC. Besides iterative formulas of control variables are improved so that the contradictions between precision and speed can be reduced. As the transmission directions of coherent beams are different in focused type CBC, GSimproved algorithm and phase correction algorithm are used to enhance the accuracy of phase, so that the performance of CBC can be enhanced.