Patent ID: 7042918

Claim:
A tunable laser source of a Littman arrangement type, comprising: a semiconductor laser and a diffraction grating fixed to an optical base; a wavelength selection mirror which rotates around a position, as a rotation center thereof, where a mode hop is suppressed at a time of a wavelength variation; a motor; a feed screw which receives a driving force of the motor at one end to be rotated, in which another end thereof is disposed at a predetermined position with respect to the optical base, and which is larger in coefficient of thermal expansion than the optical base; a first nut which is feedably fitted to the feed screw; a flat spring in which one end thereof is fixed to the first nut; and a mirror arm which has a rotation shaft disposed at the rotation center of the wavelength selection mirror, and first and second arm portions formed in a substantially V-like shape and elongating from the rotation shaft, wherein the wavelength selection mirror is fixed to the first arm portion of the mirror arm, and another end of the flat spring is fixed to the second arm portion of the mirror arm.