Measurement of the stimulated emission cross section in a waveguide $CO_2$ laser

An experimental method is described for determining the stimulated emission cross section $\sigma$ of a gas laser. The method was used to measure $\sigma$ for the $00^\circ1-10^\circ0$ vibrational transition of the $CO_2$ molecule in a compact waveguide laser having a beryllia ceramic discharge tube. The determination of $\sigma$ was based on an experimental measurement of the luminescence drop at $4,3\mu m$ wavelength, and of the laser output power at $10,6\mu m$ wavelength. The value of $\sigma_0$ measured at zero photon flux density in the waveguide resonator, for a gas mixture $Xe-CO_2-N_2-He$ at a pressure of 6.65 kPa, was $1,84\cdot10^{-18}$ cm$^2$. The effective value of the upper active-level lifetime of the $CO_2$ molecule was also determined.