On-chip Nanoseconds Tunable Microwave Photonic Narrow Bandpass Filter over a Wide Frequency Range

We propose and demonstrate an on-chip nanoseconds tunable microwave photonic narrow bandpass filter over a wide frequency range using a high-Q racetrack micro-ring resonator (MRR). In the proposed filter based on phase modulation to intensity modulation (PM-IM) conversion, the racetrack MRR is the key component, in which multimode waveguides are employed to have a low-loss optical propagation for a high Q-factor. To enable ultrafast and wide tunability of the MRR, a lateral PN junction and a top-placed metallic micro-heater are incorporated. The PN junction is leveraged to realize the ultra-fast tuning speed, and the metallic micro-heater ensures a wide frequency tuning range. A silicon-based high-Q racetrack MRR chip is designed, fabricated, and evaluated. By incorporating the chip in a microwave photonic filter system, a filter with a narrow passband of 1.2 GHz, an ultrahigh tuning speed of less than 50 ns, and an ultrawide tuning range from 3 to 51 GHz is experimentally demonstrated, which is promising to be widely used in high-resolution radar systems and high-speed wireless communication systems.