Tunable Microwave Photonic Filter Based on LNOI Polarization Beam Splitter and Waveguide Grating

A tunable microwave photonic filter (MPF) based on a polarization beam splitter (PBS) and waveguide grating true-time delay line (TTDL) is proposed and demonstrated experimentally. Taking advantage of the high birefringence property of lithium niobate (LN), the PBS is achieved by a simple structure in a short length. The TTDL consists of an LNOI waveguide grating and flexible electrodes covering along the grating. Owing to the electro-optic effect of LN, a wide tuning range and high tuning accuracy of delay time can be achieved simply by controlling the charging position of the electrodes. With the proposed PBS and TTDL, the MPF exhibits low drive voltage, low power consumption, and high response rate in a simple construction.