Optical heterodyning of radiation from an injection laser with an external dispersive resonator

The method of optical heterodyning was used to find the upper limit ($\thicksim20$ kHz) of the width of the emission line of a cw injection laser operating at room temperature in an external dispersive resonator. The precision of the measurements was limited by fluctuations of the laser emission frequency due to the instability of the optical length of the resonator.