Experimental demonstration of a single silicon ring resonator with an ultra-wide FSR and tuning range.

We present an experimental realization of a pseudo single-mode silicon ring resonator with an ultra-wide free spectral range and tuning range. The device is a single microring resonator with a tunable reflector integrated inside. The reflector is designed to have zero reflection for only one resonance of the ring, while all other resonances will suffer strong reflection. Given that the reflection inside a ring resonator leads to resonance splitting and degradation of the extinction ratio (ER), we obtain a ring resonator where only a single resonance has a large ER, while all others have a very low ER. The large ER resonance can be continuously tuned using metal heaters to achieve a broad tuning range over 55 nm with 16 mW of power injected into the phase shifter.