The numerical calculation and analysis for designing a polarization beam splitter based on a rectangular phase grating

摘要

A new method based on the combination of Finite-Difference Time-Domain (FDTD) algorithm and Fourier transform was proposed to analyze the Fraunhofer vector diffraction of gratings in this paper. The interaction of a grating with the incident linearly polarized light was simulated using FDTD algorithm, the complex amplitude distribution on the rear plane of the grating was extracted, and then the Fraunhofer diffraction pattern was obtained by performing Fourier transform of the complex amplitude. It was found that for the rectangular phase grating if the period of the grating is comparable to the wavelength of the incident wave, the propagation speeds of the TE and TM waves in the dielectric of the grating are different, which makes the diffraction of the grating is polarization dependent. Besides, the relative phase retardations of TE and TM waves formed on the rear plane of the grating are different and both of them can be controlled by changing the thickness of the grating, which makes it be realized that the intensities of TE and TM waves concentrate onto the 0th order and 1st order separately by selecting a suitable grating thickness. Therefore a polarization beam splitter based on a rectangular dielectric grating can be easily designed.