Pulsed HF chemical laser linewidth measurements using time-resolved bleachable absorption of HF gas

The spectral linewidth at 2.7 μ of a transverse discharge pulsed HF chemical laser has been measured using the saturable absorption of low-pressure HF gas in an external cell. Using the ν = 0 to ν = 1 P(J) transitions, the laser linewidth was found to be 10−4 cm−1—120 times narrower than the Doppler spectral width. Heterodyne beating between two HF lasers was observed and the pulse-to-pulse frequency shift noted.