Frequency-Tunable Active Mode-Locked Optoelectronic Oscillator Incorporating an Electrically-Switchable Silicon Photonic Micro-Ring Resonator

We propose and experimentally demonstrate a frequency-tunable active mode-locked optoelectronic oscillator (AML-OEO) for microwave pulse generation. The proposed AML-OEO has a dual-loop configuration based on phase modulation to intensity modulation conversion. In the loops, an electrically-switchable silicon photonic micro-ring resonator (MRR) with a top-placed metallic micro-heater and a lateral PN junction incorporated in the waveguide is used to play two-fold key functions. First, the MRR is employed as a narrow optical notch filter for frequency selection in the OEO implementation, and with the use of the top-placed micro-heater, the generated microwave frequency is highly tunable in a large range based on the thermal optics; secondly, the MRR is leveraged to realize the mode locking by performing the periodically high-speed gain modulation based on the lateral PN junction. An experiment is performed, and microwave pulses with a period of 1.08 μ and tunable center frequencies from 6 GHz to 18 GHz are experimentally generated. The proposed AML-OEO provides a flexible tunability and a compact structure, which is promising to be widely used in high-speed pulsed doppler radar and multi-carrier communication systems.