Laser Beam Shaping Based On Liquid Crystal Spatial Light Modulator

These properties of laser beam that its intensity distribution is Gaussian profile and propagation path is hyperbola line limit its application and development. For example, in some semiconductor processing, the flat-top beam can improve the laser energy processing window so as to increase efficiency; it is desirable to obtain a uniform intensity in laser projection printing; in laser radar and coherent imaging systems, uniform illumination is desired in the far field of the source. Therefore, it is necessary to shape the laser beam, transforming Gaussian beam into a flat-top beam. This paper use the liquid crystal spatial light modulator to achieve the Gauss beam shaping by way of real-time change of phase function of liquid crystal spatial light modulator, that is a controllable and efficient beam shaping method.The main content of the paper are as follows:Firstly, the paper analyses typical beam shaping technology in the current laser shaping field, and compares their advantages and disadvantages, describes the development present situation and the principle of liquid crystal spatial light modulator, summarizes the advantage of using a liquid crystal spatial light modulator for beam shaping.Secondly, the principle designed the phase function of liquid crystal spatial light modulator and optimization algorithms have been researched. On the basis of Gercheberg-Saxton algorithm, PMA-profile smoothing hybrid algorithm is proposed, reducing mean square error and uniformity of output beam at the same time. The phase function of liquid crystal spatial light modulator is designed by the use of the algorithm.Thirdly, beam shaping experiment based on liquid crystal spatial light modulator has been designed and realized. Using the phase-modulation characteristics of liquid crystal spatial light modulator and PMA-profile smoothing hybrid algorithm, this paper have designed the experimental light path, experimented, achieved the Gauss beam intensity shaping and obtained flat-top beam. So that using liquid crystal spatial light modulator for beam shaping in this paper, is an effective method for beam shaping.