MISALIGNMENT PREVENTION IN AN EXTERNAL CAVITY LASER HAVING TEMPERATURE STABILISTION OF THE RESONATOR AND THE GAIN MEDIUM

摘要

The present invention relates to an external-cavity laser module (20) comprising a thermoelectric cooler (TEC) (44) including an upper carrier plate (44a) having an upper surface, said TEC being configured to stabilise the temperature of the upper surface at a substantially constant temperature (T<SUB>1</SUB>). The laser module further comprises a laser assembly mounted on an optical bench (30), which is in thermal coupling with said upper surface, said laser assembly comprising a gain medium (35) for emitting an optical beam into the external cavity and an end mirror. Variations of the environmental temperature (T<SUB>env</SUB>) with respect to the thermally stabilised temperature (T<SUB>1</SUB>) cause mechanical deformations of the TEC upper carrier plate that is in thermal coupling with the laser assembly. Said mechanical deformations in turn induce variations in the optical path length of the laser cavity. The Applicant has found that the effect of mechanical deformations, i.e., the variation in the optical path length of the laser cavity, can be at least partially compensated by mechanically decoupling the optical bench from the upper surface of the TEC, while maintaining a thermal coupling between the TEC and the optical bench so as to ensure an efficient thermal stabilisation of the laser cavity. Mechanical decoupling is achieved by interposing a thermally conductive intermediate plate (28) between the optical bench (30) and the upper carrier plate (44a) of the TEC, said intermediate plate having a length along the longitudinal direction of the main optical axis of the optical beam within the laser cavity which is smaller than the length of the upper carrier plate along the same direction and the mechanical contact between the thermally conductive platform and the thermally stabilised surface takes place only through said intermediate plate. In the preferred embodiments, the external cavity laser is a tuneable laser.