Research On Issues About Holographic Maskless Femtosecond Laser Parallel Processing Based On LCoS

Femtosecond laser micro/nano fabrication has a bright prospect of a wide application. At present, the traditional processing device is laser direct writing system, it is inefficient and unable to meet production needs. If it combines with computer generated hologram, the use of the SLM loading computer-generated hologram (CGH) to achieve parallel processing design, can develop a new method of high efficiency, high resolution, small heat affected and multi-scale, which will be devoted to promoting the wide application and industrialization of femtosecond laser micro/nano processing. Therefore, shaping Femtosecond laser based on SLM has aroused wide concern. It provides an important method to better achieve micro/nano fabrication and creates an effective way for research the femtosecond laser field with novel properties. In this paper, we build a femtosecond laser holographic parallel processing system, study on the key issues by theoretical and experimental, and lay a solid foundation for further research of Holographic femtosecond laser modulation vector field in the future.This article comes from the natural science key project of anhui province (1308085ME76) and the natural science key project of China(51275502).The main contents of this paper are as follows:The foreign research status of CGH technique in micro-nanofabrication and vector field development are introduced, and some critical group’s achievements are reviewed. Then, based on the conventional two-photon writing process system, a femtosecond laser holographic parallel processing system with SLM are built, and the GS algorithm which used in the experiments to generate fourier holograms is analyzed and optimized.For the problems of pixelated SLM structure, firstly, analyzed theoretically the causes of the zero-order diffracted beam and muti-level reconstructed image, then a phase-only hologram containing digital blazed grating are designed and generated to blaze the target pattern to the peak position of zero-order interference in order to improve the energy utilization rate. Finally, four measures to eliminate the zero-order light interference combine high-pass filter are introduced, they are divergent spherical wave loaded phase technique, convergence spherical wave loaded phase technique, linearly loaded phase technique and combination of spherically and linearly loaded phase technique. Imaging experiments and pattern processing experiments both verified the rationality of the methods.For the problems of the research to the new fields, firstly, based on the preliminary research content, a convenient approach for generating vector beams in a 4f system with a SLM was built. When the numerical aperture NA of the objective lens is too large, the objective lens’s aperture, depolarization and aberration cannot be ignored. So theoretically analyzed the causes of these effects by De-bye diffraction theory and laid the foundation for the compensation work. finally, using matlab simulation,the morphology of radially polarized beam and azimuthally polarized beam are observed.