Abstract: There is provided a tunable external-cavity laser and a tunable laser source based on such tunable external-cavity laser. The tunable external-cavity laser comprises: two reflective surfaces to form a laser cavity therebetween; an active waveguide for amplifying laser light propagating in the laser cavity; a tunable wavelength-selective filter within the laser cavity for selecting the emission wavelength of the tunable external-cavity laser with in a tuning range; and a collimating lens system for collimating the optical beam out of the active waveguide for propagation in the laser cavity. The collimating lens system comprises an imaging lens and a collimating lens for collimating the optical beam. The imaging lens induces a positive chromatism within the tuning range and the collimating lens comprises a complex lens inducing a negative chromatism within the tuning range so as to at least partially compensate for the positive chromatism induced by the imaging lens.

Abstract: The present invention relates to a method of producing an optical filter, characterized in that it comprises effecting the following steps on an optical waveguide (10): controlling the varying interior profile of the waveguide, preferably by melt-drawing, and writing a Bragg grating (20), using techniques allowing independent control of longitudinal variation of the Bragg wavelength and longitudinal variation of the exterior profile of the waveguide.