Silicon-on-insulator-based microwave photonic filter with narrowband and ultrahigh peak rejection

We propose and demonstrate a silicon-on-insulator (SOI)-based widely tunable microwave photonic filter (MPF), which is implemented by using an under-coupled microring resonator (MRR) assisted by two cascaded tunable Mach Zehnder interferometers. In the experiment, the MPF achieves an ultrahigh peak rejection exceeding 60 dB, a full width at half-maximum bandwidth of 780 MHz, and a frequency tuning range of 0-40 GHz, even when the propagation loss of the MRR is 1.65 dB/cm. To the best of our knowledge, this MPF demonstrates ultrahigh peak rejection and narrow bandwidth simultaneously in SOI for the first time with MRR of such propagation loss and avoids using external electrical devices to improve the rejection. (C) 2018 Optical Society of America