Journal ArticleA novel approach to interface high-Q Fabry–Pérot resonators with photonic circuitsCheng, Haotian; Jin, Naijun; Dai, Zhaowei; Xiang, Chao; Guo, Joel; Zhou, Yishu; Diddams, Scott A; Quinlan, Franklyn; Bowers, John; Miller, Owen; Rakich, Peter<p>The unique benefits of Fabry–Pérot resonators as frequency-stable reference cavities and as an efficient interface between atoms and photons make them an indispensable resource for emerging photonic technologies. To bring these performance benefits to next-generation communications, computation, and time-keeping systems, it will be necessary to develop strategies to integrate compact Fabry–Pérot resonators with photonic integrated circuits. In this paper, we demonstrate a novel reflection cancellation circuit that utilizes a numerically optimized multi-port polarization-splitting grating coupler to efficiently interface high-finesse Fabry–Pérot resonators with a silicon photonic circuit. This circuit interface produces a spatial separation of the incident and reflected waves, as required for on-chip Pound–Drever–Hall frequency locking, while also suppressing unwanted back reflections from the Fabry–Pérot resonator. Using inverse design principles, we design and fabricate a polarization-splitting grating coupler that achieves 55% coupling efficiency. This design realizes an insertion loss of 5.8 dB for the circuit interface and more than 9 dB of back reflection suppression, and we demonstrate the versatility of this system by using it to interface several reflective off-chip devices.</p>American Institute of Physics2023-11-0110535902APL Photonics8112378-0967https://doi.org/10.1063/5.01743842137740National Science Foundation