Phase interpretation of wideband splitting for TE polarization by embedded microstructure

•The beam splitting control is presented by an embedded two-layer grating.•The bandwidth is improved for TE polarization with the 93 nm spectral range.•The physical essence can be well explained by the accumulated phase difference.

The beam splitting control is proposed by an embedded two-layer grating. With the optimized grating parameters for the special duty cycle of 0.65, the novel grating can diffract both TE and TM polarizations into two orders with the 50/50 splitting ratio, where the polarization-independent property is exhibited. Most importantly, the wide bandwidth for the incident wavelength is achieved for TE polarization compared with the reported total internal reflection grating and the surface-relief single-layer grating. The physical essence of the wideband is well explained by the accumulated phase difference based on modal method. Since it is not easy to obtain the wide incident wavelength range for the conventional multilayer coatings and the surface-relief single-layer grating, the physical mechanism can offer an effective guideline to design grating-based beam splitter with the wide bandwidth for the incident wavelength.