Fast-Reconfigurable Microwave Photonics Phase Shifter Using Silicon Microring Resonators

Thermally controlled silicon photonics microwave phase shifters suffer from slow reconfiguration time that practically limits their application fields. A microwave photonics phase shifter exploiting fast plasma dispersion effect in a silicon microring resonator (MRR) embedding a laterally-doped pn-junction waveguide operating in carrier-depletion mode has been designed and characterized. Proper dimensioning of ring parameters allows moderate insertion loss and limited RF power excursion in correspondence of wide RF phase changes as the space charge region of the junction is modulated by an applied reverse voltage. Experimental results confirm a large modulation bandwidth of more than 5GHz and a phase excursion well in excess of 360° using a cascaded MRRs pair with a residual amplitude modulation down to 2.3 dB.