Optical polarization conversion based on guided-mode resonance through a silicon film perforated by L-shaped holes

We numerically study the guided-mode resonances excited in an 80-nm-thick silicon waveguide perforated by a square array of L-shaped holes. The broken symmetry of the L-shaped holes splits the degenerate guided-mode resonances of the symmetric circular hole’s array into four nondegenerate resonances via localized resonances under normally incident light, forming multiple narrow minima in the transmitted spectra. The conversion of optical polarization is realized through the superposition of the co-polarization and the cross-polarization of electromagnetic waves radiated by guided-mode resonance.