Optically tunable single passband microwave photonic filter based on phase-modulation to intensity-modulation conversion in a silicon-on-insulator microring resonator

Abstract

We propose and experimentally demonstrate a single passband frequency-tunable microwave photonic filter (MPF) based on phase-modulation to intensity-modulation conversion in an optically pumped silicon-on-insulator (SOI) microring resonator (MRR). In the proposed MPF, a phase-modulated optical signal is filtered by an SOI MRR, to have one first-order sideband suppressed by the MRR notch. The phase-modulated optical signal is converted to an intensity-modulated single-sideband (SSB) signal and detected at a photodetector (PD). The entire operation is equivalent to a single passband MPF with the central frequency determined by the wavelength difference between the optical carrier and the MRR notch. The frequency tunability is achieved by tuning the resonance wavelength of the MRR, which is realized by optically pumping the MRR using an optical pumping source with its wavelength located at one resonant wavelength of the MRR. The thermal effect due to the free carrier absorption (FCA) and free carrier dispersion (FCD) resulted from the two photon absorption (TPA) in the MRR leads to a net redshift in the resonance wavelength, enabling the tuning of the frequency of the MPF. The approach is experimentally evaluated. An all-optically tunable single passband MPF with a tunable frequency from 16 to 23 GHz is experimentally demonstrated.