Single axial-mode selection in a far-infrared p-Ge laser

Single axial-mode operation of the pulsed far-infrared p-Ge laser with an intracavity Fabry-Perot type frequency selector has been observed by means of Fourier-transform spectroscopy. A spectral resolution better than 1 GHz has been achieved on an ordinary continuous-scan spectrometer using the event-locked technique for pulsed emission sources. A laser active-cavity finesse of at least unity has been directly confirmed from the measured emission spectral width. Analysis of the envelope of the corresponding interferogram suggests that the finesse exceeds 10. (C) 2000 American Institute of Physics. [S0003-6951(00)00215-1].