Laser Beam Shaping Using Liquid Crystal Spatial Light Modulator

As a high-quality light source, laser technology has been widely used in our productions and lives. However its Gauss energy distribution limits its further development. The fields of laser radar, laser welding, inertial confinement fusion and optical processing require the laser beam has a uniformity of intensity distribution. Therefore, it is necessary to shape the laser beam into a flat-top beam. Based on the needs of real-time beam shaping, this paper designs a scheme to make beam shaping using the liquid crystal spatial light modulator (LCSLM). Numerical simulation and experimental research are carried out to prove the possibility of the scheme. The main works are as follows:Firstly, the history and conventional methods of the beam shaping technology are introduced. Then the electro-optical properties of twist nematic liquid crystal and the modulating principle of LCSLM which demonstrates the feasibility of using the phase-only LCSLM as an optical element to take laser beam shaping is introduced chiefly.Secondly, a diffractive model for beam shaping is proposed based on the scalar diffraction theory. On the basis of adaptive regularization algorithm, an improved algorithm named input output-adaptive regularization (IO-AR) algorithm is proposed. This algorithm is carried out by mixing the input-output algorithm and adaptive regularization algorithm. Computer simulations show an excellent trade-off between the energy concentration and beam uniformity of the output beam while maintaining low mean square error.Thirdly, a beam shaping experimental platform based on HOLOEYE’s LC2002is set up. Experiment using the IO-AR algorithm is carried out. Experimental results show this approach could gain the flat-top beam and it is an effective approach for laser beam shaping.