Theoretical Simulating And Experiment Research Of Beam Shaping Based On Liquid Crystal Spatial Light Modulator

The output beam of a laser usually has its typical intensity distribution, whichoften affects the energy efficiency in practical application. To improve the utilizationefficiency of the laser beam, it is required to transform the output laser intensitydistribution into a specific intensity distribution. In this paper, numerical simulationand experimental research of beam shaping are carried out by using pure phase liquidcrystal spatial light modulator(LC-SLM), which are based on physical optics method.The main contents are listed as follows:1. The conventional beam shaping methods are described, which includebirefringence lenses, binary optical elements, random phase plate and LC-SLMThe methods mentioned above belongs to geometrical optics method and physicaloptics method respectively. In addition, the advantages of using LC-SLM arediscussed.2. A mathematical model for beam shaping is introduced under the physical opticsmethod, which is based on the Helmholtz equation and the scalar diffractiontheory. The physical nature of beam shaping is discussed which laid a theoreticalfoundation for algorithm research.3. GS algorithm, simulated annealing algorithm are introduced in terms of theirprinciples, algorithm structures and computation steps. Two improved algorithmsare proposed: one is the GSSA algorithm which is a integration of GS algorithmand simulated annealing algorithm; the other is the simulation annealing algorithmwith Zernike polynomials.4. Numerical simulation and comparison of beam shaping algorithms are carried out.By using GS and simulated annealing algorithm combined with Zernikepolynomials, numerical simulations of beam shaping for converting a Gaussianintensity distribution to a super-Gaussian intensity distribution, a square flat-topintensity distribution, a hollow super-Gaussian intensity distribution are carriedout. The conversion of a hollow super-Gaussian intensity distribution to asuper-Gaussian intensity distribution has also been analyzed. GS algorithm, simulated annealing algorithm, GSSA algorithm are compared in terms ofconvergence precision and computing time.5. A closed-loop adaptive beam shaping system is set up based on liquid crystalspatial light modulator. Using simulated annealing algorithm combined withZernike polynomials, experimental research of beam shaping is carried out. Theexperimental and simulation results are compared and the feasibility of theapplication of algorithm in beam shaping is verified.In summary, this paper focuses on the theory of beam shaping algorithm andexperimental research. The basic principle of beam shaping and algorithm theories arediscussed. On the basis of discussing the theoretical foundation and traditionalalgorithms of beam shaping, two improved algorithms are proposed and the efficiencyof the algorithms are simulated. Beam shaping experiments using simulated annealingalgorithm combined with Zernike polynomials are implemented. This research workplays a key role in improving the near-field beam intensity distribution and promotingthe development of beam shaping technology.