Continuously tunable delay line based on eye-like ring resonator

We proposed a proof-of-concept silicon-on-insulator (SOI) compatible tunable delay line. The thermally controlled eye-like ring resonator add/drop filter is utilized. By controlling the optical power coupling into the resonator through the temperature-controlled Mach Zehnder Interferometer (MZI) power splitter, a continuously tunable group delay is obtained. A considerable group delay of 627 ps can be achieved in over-coupling condition while maintaining the optical loss less than 25 dB. Particularly when the resonator is under-coupled, maximum pulse advancement of 574 ps with similar transmission exists which extends the span of tunability from slow light to fast light in a single device. With the eye-like resonator, a total tunable range exceeding 1 ns is achievable and the overall device foot print can be kept smaller than 0.019 mm2.