Silicon photonic coupled-ring resonator in nested configuration comprising different length scales

Silicon photonics is continuing to develop for an increasing number of applications including data centers, miniaturized sensors and atomic clocks. The development involved the creation of the technology platform, design of innovative devices and developing models and methods for fabrication tolerance assessment. In our work, we suggest a novel structure for silicon photonic coupled-ring-resonator with an order of scale difference in the rings' lengths and sensitivity analysis for this structure. The design consists of a long racetrack resonator of length 472.6 µm (sub-millimeter scale) nested by ring resonator of radius 25 µm, This radius was chosen to minimize bending losses. The coupling ratio of the directional couplers is designed to be 97/3. The suggested structure is fabricated by the IMEC fabrication facility which is using DUV lithography and silicon etching ePIXfab. The analysis shows that this structure can achieve higher finesse than the typical values of the conventional structure, even with reasonable fabrication tolerance. Experimentally a finesse of about 25 and a quality factor of about 17,000 is achieved. The proposed structure can improve the performance of optical sensing and filtering.