Time-resolved linewidth and lineshape measurements of a pulsed optically-pumped far infrared D2O laser

The spectral composition of the emission from an optically-pumped D2O far infrared laser around the 385-micron line was measured as a function of time during a 1-microsec duration. A multichannel heterodyne receiver comprising a Schottky barrier diode providing a spectral resolution of 80 MHz was used. A spectral shift of the laser emission during the pulse was observed, which was caused by the AC Stark effect, but other mechanisms may also play an important role. The emission spectra were studied as a function of instantaneous pump power and time for different D2O pressures. Since the D2O laser contains no frequency selective elements, multimode emission and mode competition effects lead to a complex behavior. An attempt is made to explain the observations on the basis of a theoretical model. (I.E.)