Tunable coupling-induced resonance splitting in a self-coupled silicon ring cavity with robust spectral characteristics.

We propose and demonstrate a self-coupled micro-ring resonator for resonance splitting by mutual mode coupling of a cavity mode and a counter-propagating mode in a silicon-on-insulator platform. The resonator is constructed with a self-coupling region that can excite a counter-propagating mode. We experimentally study the effect of self-coupling on the resonance splitting, resonance extinction, and quality-factor evolution and stability. Based on the coupling, we achieve 72% of the free spectral range (FSR) splitting for a cavity with an FSR of 2.1 nm with <5% variation in the cavity quality factor. The self-coupled resonance splitting shows a highly robust spectral characteristic that can be exploited for sensing and optical signal processing.