Design of a broadband polarization controller based on silicon nitride-loaded thin-film lithium niobate

A novel design of a polarization controller based on "etch-less" Si3N4-loaded thin film LiNbO3 is described. Broadband operation in the spectral range between 1.45 and 1.65 mu m is achieved by using a mode evolution TM/TE splitter/converter, two mode evolution 3-dB couplers, and two electro-optic phase shifters. Numerical simulations show that the on-chip insertion loss should not exceed 1 dB. A single TE-mode output can be adjusted by applying control voltages lower than 10 V for an arbitrary input polarization state.