Silicon-Based On-Chip Fully Tunable Optical Fabry-Perot Filter Based on Multi-Mode Waveguide

As a basic optical filter configuration, A Fabry-Perot (FP) resonator has found extensive applications in laser excitation, sensing, and optical communication. Here, we propose an on-chip fully tunable silicon photonic FP filter based on multi-mode waveguide. The proposed FP filter has a low-loss multi-mode rib waveguide and two Sagnac loop mirrors (SLMs), which is of help to achieving a high Q-factor. By controlling the voltages applied to the micro-heaters placed on top of the multi-mode waveguide and directional couplers of the SLMs, the effective length of the cavity and the reflectivity of the SLMs can be tuned, leading to the fully tuning in resonance wavelength and bandwidth. A chip is designed and fabricated, which has a narrow passband of 2.7 pm, corresponding to a loaded Q-factor of
$0.6\times 10^{{6}}$
. By controlling the voltages, its resonance wavelength can be tuned in a range of 0.27 nm, and the 3-dB bandwidth can be tuned from 2.0 to 25.1 pm. With the use of the fabricated chip, a fully tunable microwave photonic filter is experimentally demonstrated. The proposed FP filter has a high Q-factor and flexible tunability, which holds potential in the applications of microwave photonic signal processing systems and optical communication networks.