DIFFERENTIAL WAVELENGTH METER FOR LASER TUNING

A simple interferometer for matching the wavelengths of tunable lasers is described. Our interferometer uses the angular dispersion of a dif fraction grating at the Littrow angle to produce a tilted wavefront wi th respect to a reference mirror in an opposing arm of a Michelson int erferometer. As a first step, the resulting interference pattern is ad justed to produce a null frill using a reference laser as a wavelength standard. When a tunable laser, such as a laser diode, is used to ill uminate the system, the laser is simply tuned to reproduce the null fr inge pattern established using the reference laser. When so tuned, the wavelength of the tunable laser is matched to that of the reference l aser within about 3 GHz, close enough for optical heterodyning.