The fir water vapor laser

Abstract

A few power measurements were taken at 79 μm . They were less than O.l mW and varied in the same way with the gas additives as at 220 μm .

A kinetic model was developed which seems to agree with the observed data. The major features of this model are that the dominant pumping mechanism is by electron impact, the rotational levels are thermalized at the gas temperatures, and the vibrational levels are thermalized at two slightly different temperatures. In terms of this model it appears that hydrogen and helium improve laser gain by cooling the bending mode vibrational temperature.

A detailed study of an electric discharge CW water vapor laser oscillating on the ll8.6 and 220 μm lines has been made. A novel technique for determining small signal gain and internal laser losses by using a Michelson coupler to measure the threshold and optimum coupling coefficients was also developed.

The effect of adding hydrogen and helium was documented. For the same discharge conditions at a current of 1.8 A, the following changes were observed: Laser power at ll8.6 μm increased by an order of magnitude from 1.5 to 15 mW. At 220 μm, it increased from 0.26 to 1.3 mW. Small signal gain increased, from 0.50 and 0.27% m⁻¹ to 0.74 and 0.33% m⁻¹ on the ll8.6 and 220 μm transitions, respectively. Electron temperature dropped from 6 eV to less thah 5 eV. Electron density increased from 1.3 x 10¹⁰ cm⁻³ to 1.75 x 10¹⁰ cm⁻³ with helium, but remained unchanged with hydrogen.