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 i ntracavity Fabry-Perot type frequency selector has been observed by means o f Fourier-transform spectroscopy. A spectral resolution better than 1 GHz h as been achieved on an ordinary continuous-scan spectrometer using the even t-locked technique for pulsed emission sources. A laser active-cavity fines se of at least unity has been directly confirmed from the measured emission spectral width. Analysis of the envelope of the corresponding interferogra m suggests that the finesse exceeds 10. (C) 2000 American Institute of Phys ics. [S0003-6951(00)00215-1].