Patent ID: 8311067

Claim:
A system comprising: an external cavity laser having a laser cavity comprising: a laser medium for generating laser light; a movable wavelength tuning element spaced from the laser medium for receiving at least a portion of the laser light; and two or more partially reflective optical surfaces which provide feedback of laser light to the laser medium and define the operating mode of the laser cavity; a positional light source which generates positional light; and a position sensitive detector which receives at least a portion of the positional light; wherein the positional light source is connected to the wavelength tuning element so that, as the wavelength tuning element moves, the positional light source moves along a track; wherein, in receiving the portion of the positional light, the position sensitive detector thereby determines a position of the wavelength tuning element based on movement of the positional light source along the track; wherein the laser comprises a laser diode; wherein the wavelength tuning element is a diffraction grating, and wherein the laser cavity is positioned between the laser diode and the diffraction grating; wherein the diffraction grating pivots about a pivot point within an angular range, and wherein the position sensitive detector thereby determines an angular position of the diffraction grating; wherein the positional light source is mounted on a positional light source mount, wherein the positional light source mount is connected to a second end of the grating frame spaced from the one end for pivotal movement about the pivot point so that the positional light source travels along a curved track, and wherein the position sensitive detector detects a position of the positional light source along the track.