Active compensation for critical coupling deviation on a single-arm silicon microring by free-carrier absorption

We present active critical coupling compensation by employing the free-carrier absorption for a single-arm silicon microring device when the microring has fabrication error to deviate from critical coupling. It is possible to re-establish the critical coupling for the MOS capacitor microring by applying gate voltage within 10 V when the gap width fabrication error is within the ITRS 90 nm CMOS technology node.