Broadband microwave photonic phase shifter based on a feedback-coupled microring resonator with small radio frequency power variations.

An on-chip microwave photonic phase shifter based on an electrically tunable feedback-coupled microring resonator (FCMR) is proposed and experimentally demonstrated. By properly adjusting the voltage applied on the FCMR, the transmission spectrum with different optical extinction ratios is realized while the phase shift range remains almost unchanged. This proposal solves the conflict between the large range of phase shift and small radio frequency (RF) power variation in the ring-resonator-based microwave photonics phase shifter. Finally, a microwave photonic phase shifter with phase tuning of over 172 deg from 20 to 30 GHz is obtained, and the RF power variation can be compressed less than 5 dB under a certain status tuned by the bias voltage.