Dynamics of the N2O Laser as Measured with a Tunable Diode Laser

Abstract

The work presented in this thesis was undertaken to explain the differences in output powers and small-signal gain coefficients observed in cw N20 and C02 lasers. To isolate the factors limiting small-signal gain, the dynamics of conventional cw N20 laser discharges were investigated using a tunable diode laser (TDL) operating in the 2120-2350 cm-1 frequency region. Absorption measurements were made with the TDL on more than 10 different vibrational bands, allowing vibrational population distributions in the three normal modes of vibration of N20 to be determined. The vibrational populations follow a Boltzmann distribution, and the v1 and v2 mode temperatures are found to be strongly coupled, and to maintain equilibrium with the background gas temperature under all discharge conditions. It is observed that the v3 mode temperature saturates at high discharge currents. This saturation, which is attributed to electron de-excitation, is determined to be the primary factor limiting small-signal 10-μm gain in the N20 laser and is much more important than N20 dissociation. The maximum small-signal gain coefficients achievable in cw N20 lasers are calculated, and the results of the work indicates the measures that must be taken to optimize small-signal gain in the N20 laser.