Synchronous tuning of extended cavity diode lasers: the case for an optimum pivot point

Diode lasers can be tuned by simultaneous rotation and translation of an ex ternal grating. This can be achieved by rotating the grating about a displa ced pivot point. We derive the tuning range as a function of pivot point po sition for various extended cavity geometries. In each case, the geometric problem reduces to the solution of a quadratic equation. For near-infrared wavelengths, placement of the pivot is relatively noncritical for tuning ra nges of the order of 10 GHz, but requires millimeter accuracy for a tuning range >100 GHz. (C) 1999 Optical Society of America.