Polarization-independent two-port beam splitter grating under second Bragg incidence angle with usual duty cycle

Based on the total internal reflection (TIR) under second Bragg incidence angle, polarization-independent two-port beam splitter grating etched in fused silica is described for the usual duty cycle of 0.5. There are three diffraction orders in the reflection: –2nd order, –1st order, and 0th order. The grating depth and period are optimized using the rigorous coupled-wave analysis (RCWA) in order to separate the incident wave into the –2nd and 0th orders with good uniformity and high efficiency for the TE and TM polarization wavelength of 800 nm. The diffraction properties for operation have been investigated for the incident wavelength and angle, indicating that good tolerance of incidence angle can be obtained for the designed beam splitter grating. Most importantly, the advantages of usual duty cycle of 0.5 and much shallower-etched depth will facilitate effective fabrication the reported beam splitter, which is of great significance for the practical use in numerous optical systems.