An external-cavity tuneable laser includes a gain medium and a tuneable mirror wherein at least the tuneable mirror is in thermal contact with a thermally conductive platform. The tuneable mirror lays substantially horizontally on the thermally conductive platform significantly improving the thermal contact of the tuneable mirror with the platform. A laser beam from the gain medium is directed onto the tuneable mirror, which is mounted substantially horizontally with respect to the thermally conductive platform, by means of a deflector that deflects the beam or a large part of it toward one of the principal surfaces of the tuneable mirror. The resulting laser cavity is a folded cavity. The thermally conductive platform is preferably thermally coupled to a TEC that provides thermal control for the platform. The deflector may be a beam splitter that deflects part of the incoming light and transmits the remaining part. According to a preferred embodiment of the invention, the portion of light transmitted through the beam splitter forms the output laser beam, i.e., the external-cavity laser outputs a laser beam on the side of the wavelength selective elements (the tuneable mirror and, if any, the channel grid), i.e., on the side of the front facet of the laser diode.