Widely tunable all-active microring lasers through phase shifted controlled feedback

A tunable laser based on an InGaAsP-InP microring resonator with multimode interference coupler is demonstrated. Tuning ranges from 18 to 30 nm are achieved and mappings of the tunable operation are experimentally produced and analyzed. The observed tunability is the result of the interaction between counterpropagating ring modes through back-reflection from the device facets.