Modeling of injection seeding of a pulsed high pressure CO2 laser

A computer model for injection seeding of a high pressure CO2 laser is presented. A rate equation model is used to predict single longitudinal mode (SLM) operation through injection of a cw seed into the resonator cavity. The coupled non-linear differential equations are solved using a Runge-Kutta method. Predictions for the minimum injection power required to produce SLM pulses are made. Detuning off resonance and the effect of the output coupler reflectivity and small signal gain on SLM operation is also considered. Conditions for stable SLM operation through injection of a cw seed are suggested. Single mode operation, even in the detuned case, can be attained due to the homogeneous broadening of the gain, and the rapid growth of the pulse under high gain conditions.