Fabry-Perot fringe enhancement.

The experimental results are presented to show that it is possible to use a Fabry-Perot interferometer to discriminate multifrequency, uniphase gas laser modulation at frequencies less than the laser's doppler bandwidth. This is done by selecting the F.P. mirror spacing to match the laser cavity. Thus, each F.P. mode discriminates the modulation on its own laser mode. If all of the laser modes are modulated by the same amount, the F.P. modes will discriminate the laser modes in phase to produce F.P. fringe enhancement at the output. This scheme was demonstrated with both a 30-cm and a 120-cm laser-F.P. combination.