Patent ID: 7961769

Claim:
A wavelength tunable semiconductor laser device, comprising: an active region for oscillating a laser beam; and a wavelength tuning region for shifting a wavelength of the laser beam, wherein a thermal compensation region is provided adjacent to the wavelength tuning region, the thermal compensation region receiving an input of an electric power and converting most of the inputted electric power to heat, the sum of the electric power inputted into the thermal compensation region and an electric power inputted into the wavelength tuning region being always kept constant, wherein the thermal compensation region is comprised of a non-active waveguide having a first single mesa structure, wherein most of the inputted electric power is converted to heat by injecting an electric current into the non-active waveguide or applying a voltage to the non-active waveguide, wherein the active region and the wavelength tuning region are comprised of a waveguide having a second single mesa structure other than the first single mesa structure, and wherein the distance between the first single mesa structure and the second single mesa structure is greater than or equal to 3 μm and less than or equal to the thickness of a substrate of the wavelength tunable semiconductor laser device.