A tunable optical waveguide ring resonator for microwave photonic filtering

A tunable optical waveguide ring resonator is proposed and demonstrated for microwave photonic filtering. The ring resonator consists of a Mach-Zehnder interferometer (MZI) as the tunable coupler and two micro-heaters as the thermal-optic phase shifters. It was fabricated with polymer PSQ-Ls by a novel and simple UV-based soft imprint technique. The coupling states, over-, critical- and under-coupling, were obtained with the phase shifter on the arm of MZI and the maximum notch depth of about 18dB was achieved. The resonant frequency can also be tuned with the phase shifter on the ring waveguide. The notch filtering function to obtain single sideband RF signal was realized with the tunable ring resonator.