New Discharge Pumping Method for CO2 Lasers.

摘要

A pulsed CO2 laser system has been designed, fabricated, and successfully tested. Laser pulses have been generated with measured output energy of 600 mJ, pulse length 40 microsecond, and conversion efficiency of 14% in a 3:2:1 (HeN2:CO2) gas mixture. The laser operates at a total gas pressure between 5 and 40 Torr, and utilizes the COLD-I all-solid-state CO2 laser driver developed by SRL. Typical current, voltage, and laser output traces are presented and compared to numerically simulated curves, showing reasonable agreement. The theoretical model of CO2 laser discharges has been extended and utilized to analyze the steady state solutions and stability criteria for three regimes of operation: the stiff voltage case, the stiff current case, and the finite external impedance case. Numerical solutions are presented for the temporal evolution of the electron (plasma) density, the metastable density, and the electric field under various conditions. The theory of RF discharge stabilization has been extended to two spatial dimensions, and numerical results are presented for the stiff current and the stiff voltage cases. In a repetitively pulse CO2 laser, the lasing gas must be cooled between pulses to preserve efficiency. Conduction cooling has been examined by SRL as an advanced alternative to the traditional flow loop approach. This concept minimizes the weight of the laser head. A thermal analysis of a pulsed CO2 laser head with conduction cooling is presented, along with a discussion of beam quality effects due to acoustic and thermal processes. (jhd)