INTER-TRANSVERSE-MODE INJECTION LOCKING AND SUBTHRESHOLD GAIN MEASUREMENTS IN A CO2 WAVE-GUIDE LASER

A higher order CO2 waveguide laser resonator mode has been studied bot h above and below threshold, by reinjecting a frequency shifted portio n of the laser output back into the resonator, The relative reinjected (autodyne) gain profile in the vicinity of the subthreshold transvers e mode is shown to shift in frequency, reduce in spectral width, and i ncrease in magnitude as the subthreshold mode is brought nearer to thr eshold by tilting one of the resonator mirrors, Once above threshold, intertransverse-mode injection locking has been demonstrated, and clos e to the locking-point higher order terms from the nonlinear interacti on are clearly evident.