Patent ID: 7496118
Filing Date: 2009-02-24
Classification: H01S

Abstract:
1. An external cavity resonator type tunable light source comprising: a base; a semiconductor laser, which is fixed to the base, and includes at least one low reflectance, light emission facet; a collimator lens which is fixed to the base and converts light emitted from the low reflectance facet of the semiconductor laser into a parallel light beam; a diffraction grating which is fixed to the base and receives and diffracts the light beam from the collimator lens at a predetermined incident position on and at a predetermined incident angle to a diffraction face on which a plurality of diffraction grooves is provided in a direction substantially perpendicular to the base; a turnable mirror which is fixed to the base and has a mirror surface positioned opposite the diffraction face of the diffraction grating, the mirror surface being arranged to receive a diffracted light beam from the diffraction grating, make the received light beam incident to the diffraction face of the diffraction grating again in a reverse optical path, and return the incident light beams to the semiconductor laser, and which is formed so as to enable the reflection face to be reciprocally turned at a predetermined angle range and around an axis defined as a turning center, which is parallel to the diffraction groove and is on a plane extending from the diffraction face of the diffraction grating, wherein a resonator length determined depending on an optical path length from an effective end facet of the resonator to the turnable mirror surface via the diffraction grating is changed by turning the turnable mirror surface to sweep a wavelength of the emitted light from the semiconductor laser; and a stationary mirror which is fixed to the base and arranged so as to make the light beam emitted from the semiconductor laser via the collimator lens incident from a predetermined direction to a predetermined position of the diffraction grating at the side of the mirror surface of a virtual plane extending from the turnable mirror surface and at the side of the diffraction face of a virtual plane extending from the diffraction face of the diffraction grating, wherein the semiconductor laser, the collimator lens, the stationary mirror, the diffraction grating and the turnable mirror are fixed to the base so that all of these components of the external cavity resonator type tunable light source are integrated in connection with the base, wherein the semiconductor laser and the collimator lens are arranged at the side of the mirror surface of a virtual plane extending from the turnable mirror surface, and an optical path length from the effective end facet of the resonator to the collimator lens, the stationary mirror, the predetermined position of the diffraction grating, and the turnable mirror surface is substantially equal to the resonator length, wherein the turnable mirror comprises: a frame to which MEMS are applied and having a silicon substrate, the frame including a top plate, a bottom plate and a pair of side plates in a transversely rectangular frame shape; a transversely rectangular reflection plate which is arranged concentrically inside the frame, and includes a mirror surface for reflecting the light beam at least at one face side thereof; a pair of link sections arranged on one straight line from inner edge centers of the top plate and the bottom plate of the frame, opposed to each other, to an upper edge center and a lower edge center of the reflection plate to link between the top plate or the lower plate of the frame and the reflection plate, the link sections being torsionally deformable to turn the reflection plate; and drive means for applying an external force to the reflection plate to cause the reflection plate to turn in the predetermined angle range around a line connecting centers of the pair of link sections defined as the turning center; and wherein a relationship r=(L “r” is a distance from the turning center to the predetermined incidence position of the diffraction face of the diffraction grating; “L “L “L α is a light incidence angle from the stationary mirror to the diffraction face of the diffraction grating.