This paper presents a fast and rigorous design method for grating-based metal-free polarizing filter applications using two-step\nhybrid optimization techniques. Grating structures utilizing the total internal reflection in a lamellar configuration were used\nto achieve metal-free solution, which is a key technology in the chirped pulse amplification for high power laser system. Here\ntwo polarizing filters were designed: polarization sensitive and polarization insensitive. Those polarization performances were\ncharacterized by the rigorous coupled-wave analysis (RCWA), and the design parameters of grating structures, pitch, depth, and\nfilling factor were optimized by two-step hybrid optimization procedure because the diffraction characteristics of grating-based\npolarizing filters are highly sensitive to small changes in design parameters. The Taguchi method is incorporated into selection\nprocess in the genetic algorithm, which indicates that the Taguchi method optimizes the design parameters in a coarsemanner, and\nthen, coarsely optimized parameters are finely optimized using the genetic algorithm. Therefore the proposed method could solve\nglobal numerical optimization problems with continuous variables. The proposed two-step hybrid optimization algorithm could\neffectively optimize the grating structures for the purpose of polarization filter applications, and the optimized grating structures\ncould selectively filter the incident light up to 99.8% as to TE or TM waves.
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