Polarization-dependent gain and saturation energy density in a TE N2-laser amplifier

Abstract

The polarization-dependent gain, g0, and saturation energy density, Es, in a TE N2-laser amplifier were measured, using an oscillator–amplifier laser system for different amplifier electrode gap separations, dAMP, of 7, 9 and 4mm and gas pressure of p=77, 60, and 165Torr, respectively. It was realized that for the amplifier with the gap separation of 7 and 9mm, where the pdAMP-value has its optimum-value of 54Torrcm, the gain-coefficient for the input beam with the polarization parallel to the discharge electrodes (P-polarized beam) is slightly higher than the case when the beam polarization is perpendicular to the discharge electrodes (S-polarized beam). In this case, the depolarization ratio for dAMP=7mm is the range of ∼0.998 to ∼0.962 as the input voltage increases from 12 to 15.5kV, having a minimum of 0.937 around 14kV. For the Es-parameter, the reversed order is true. Also, it was found that the saturation energy densities for three states of polarization are linearly related to the output energy densities, having different slopes of 0.11, 0.14, and 0.17 for R (randomly), P- and S-polarization, respectively. The present measurement supports qualitatively the prediction of polarization–inhomogeneity model for the stimulated emission cross-section, showing that randomly oriented dipoles exhibit slightly larger gain on the direction of the electric field.