Single-electrode-tuned mode-hop-free tunable laser based on ring coupled cavity.

A novel tunable laser which can achieve mode-hop-free single-electrode tuning based on a ring coupled cavity is proposed. The device comprises of a passive ring resonator coupled to two optical waveguides, two far ends of which are terminated by partially reflecting mirrors to constitute a Fabry-Perot (FP) cavity. The waveguide in the ring resonator is divided into a tuning segment and a bias segment. The FP cavity contains an active gain waveguide and passive waveguide segments. A tuning electrode covers the tuning segment inside the ring resonator and the passive waveguide segments in the FP cavity. Mode-hop-free operation with a single-electrode tuning is achieved by properly designing the tuning electrode lengths within the FP cavity and within the ring resonator. Numerical analysis shows that a large mode-hop-free tuning range (>6 nm) with a very high single-mode selectivity can be achieved with an injection current less than 100 mA.