A Silicon Photonic Integrated Frequency-Tunable Microwave Photonic Bandpass Filter

We report a fully integrated microwave photonic passband filter on a silicon photonic chip. The on-chip integrated microwave photonic filter (IMPF) consists of a high-speed phase modulator (PM), a thermally tunable high-Q micro-disk resonator (MDR), and a high-speed photodetector (PD). The bandpass filtering function of the IMPF is implemented based on phase modulation and phase-modulation to intensity-modulation conversion, to translate the spectral response of an optical filter, which is the MDR in the IMPF, to the spectral response of a microwave filter. By injecting a CW light from a laser diode (LD) to the PM, a passband IMPF with a broad tuning range is demonstrated. Thanks to the ultra-narrow notch of the MDR, a passband IMPF with a 3-dB bandwidth of 2.3 GHz is realized. By thermally tuning the MDR, the center frequency of the IMPF is tuned from 7 to 25 GHz, achieving a tuning range of 18 GHz at a power consumption of 1.58 mW. This successful implementation of an IMPF marks a significant step forward in full integration of microwave photonic systems on a single chip and opens up avenues toward real applications of microwave photonic filters.