A simplified model for predicting gain, saturation, and pulse length for gas dynamic lasers

A single time-scale model is developed to describe the 10.6-μ laser energy extraction from an initially inverted N2-CO2catalyst mixture where the energy is stored primarily in the N2vibration. This condition is typical of high-pressure gas dynamic lasers, but the methods are general and applicable to other systems. In the absence of external pumping, the nitrogen can be regarded as an energy source that is depleted on a time scaleτ = (1 + I₀/I), the minimum possible time scale governed by collisional processes, τ determines the pulse time forQ-switched laser mixtures or the required streamwise cavity length for CW gas dynamic lasers. The derived saturation intensity I0also appears in the expression for saturated gain (for collision broadened cases)g = g₀/(1 + I/I₀), where g0is approximately the small signal gain at a given nitrogen vibrational temperature, g0decays on the same intensity-dependent time scale τ as the nitrogen vibrational energy.