We design a three-layer rectangular-groove dielectric transmission grating that can be used as a polarization-selective beam splitter. For TE polarization, the grating is equivalent to a high-efficiency grating. For TM polarization, a good splitting ratio can be exhibited with 48.4%/48.8% output. Each thickness of the three grating layers can be approximately calculated by using modal method based on the physical theory of two-beam interference with the chosen duty cycle of 0.41 and period of 690 nm for an operating wavelength of 800 nm. In order to obtain accurate grating layer thickness, the rigorous coupled-wave analysis based on Maxwell's theory is used to calculate the diffraction efficiency. The polarization-selective beam splitter grating reported previously can work only at the special prescribed incident angle or narrow angular width. The three-layer dielectric grating is aimed to obtain the wide incident angular bandwidth.
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