Patent ID: 7664156

Claim:
A wavelength tunable laser comprising: a multiple ring resonator where a plurality of ring resonators is combined; an input/output unit for inputting/outputting an optical signal to/from the multiple ring resonator; a reflection unit for reflecting the optical signal outputted from the multiple ring resonator and returning the optical signal to the multiple ring resonator; a substrate in which the multiple ring resonator is formed; a heat supply unit arranged on the substrate for providing heat to the plurality of ring resonators and controlling a resonant wavelength of the plurality of ring resonators; and a thermal conduction restraining unit for limiting heat supply from the heat supply unit only to a particular ring resonator and shutting off heat supply to remaining ring resonators; wherein the multiple ring resonator comprises a plurality of ring resonators for wavelength tuning and a ring resonator for wavelength fixing, wherein the thermal conduction restraining unit is an adiabatic groove formed in the substrate, and wherein the adiabatic groove is positioned outside of one of the ring resonators for wavelength tuning, and is formed in a circular arch shape along with the ring resonator for wavelength tuning.