Microwave photonics phase shifter with small radio-frequency power variation based on Coupling-modulated Microring Resonators

We propose and experimentally demonstrate an on-chip microwave phase shifter based on Coupling-modulated Microring Resonators (CMR). CMR is a structure that connected the transmission port and upload port of the normal ring resonator. In this case, the transmission spectrum can be tuned by properly adjusting the phase shift accumulation in the connected waveguide of the CMR. A deep notch of the transmission spectrum with 16 dB extinction ratio and 3-dB bandwidth of 17 GHz is chosen to achieve the phase shifter. And a phase shift ranging from 15 to 199 degree at 15 GHz with a radio-frequency power variation more than 7 dB is realized. After applying 1V voltage on the CMR, the extinction ratio changed to 5 dB. A quasi-linear phase shift range from 35 to 177 degree at 15 GHz with a radio-frequency power variation less than 2.5 dB is obtained. In addition, the characteristic of the phase shift at 20 GHz and 25 GHz is also tested and investigated. Moreover, this experiment indicates that the CMR has potential to solve the conflict between the large range of phase shift and small radio-frequency power variation in the ring resonator based phase shifter.