Polarization beam splitter based on the asymmetric directional coupler of lithium niobate film

A polarization beam splitter (PBS) based on a lithium niobate film asymmetric directional coupler is proposed. The PBS is located on a lithium niobate platform on an insulator consisting of a silicon nitride-lithium niobate waveguide (SLW) and a lithium niobate waveguide (LNW). By rationally designing the SLW and LNW sizes, TE polarization satisfies the phase matching condition and TM polarization phase mismatch. The numerical simulation results show that the extinction ratio (ER) and insertion loss (IL) of PBS for TE mode are 30.57 and 0.66 dB, respectively, and the ER and IL of PBS for TM mode are 28.15 and 0.11 dB, respectively, at an operating wavelength of 1.55 µm.