A method and an apparatus for tuning a laser includes creating a laser with a path between a cavity end element and a tuning element of an external cavity, both being a high reflective or semitransparent mirror, selecting at least one longitudinal mode of the laser by introducing a dispersion element in the path of the laser, rotating the tuning element about a pivot axis theoretically defined by the intersection of the surface planes of the cavity end element, the dispersion element and the tuning element to tune the laser. The method and apparatus also include provisions for moving the dispersion element along such a predetermined path to at least partly compensate a shift between the real position of the pivot axis and the theoretically defined position.