4.3-MICRON Transversely Excited Carbon Dioxide Laser Dynamics.

This thesis describes a detailed study of the dynamics of the 4.3-(mu)m CO(,2) laser. Pulsed laser action at 4.3-(mu)m is achieved by using a 10.4-(mu)m sequence CO(,2) laser to optically pump CO(,2) molecules which have been excited in a discharge. Quantitative data regarding the processes involved in 4.3-(mu)m lasing are presented, and techniques for optimization of performance are described. Single -line output energies of 15 mJ/pulse and peak powers of 100 kW/pulse are obtained using a conventional transversely -excited (TE) CO(,2) discharge 88 cm in length. Furthermore, it is shown that pulse energies are scalable to several hundred millijoules. The construction of a high power sequence CO(,2) pump laser is discussed in detail. The laser utilizes an atmospheric pressure TE discharge 88-cm long and an intracavity hot CO(,2) cell. Output energies of up to 6 J/pulse are obtained. Other work involves the characterization of discharge-excited CO(,2) and the optimization of discharge operation. Several discharge parameters are measured including mode temperatures, collision-broadened linewidths, and overlapping gain and absorption coefficients. These measurements provide accurate input data for a rate-equation model of the 4.3-(mu)m laser. The study of 4.3-(mu)m dynamics involves extensive measurements of small-signal gain and energy extraction. By making quantitative comparisons between these measurements and the rate-equation model, the influence of various parameters on the operation of 4.3-(mu)m lasers is examined. The factors which dominate the dynamics of 4.3-(mu)m lasers are found to be the short collisional lifetime of the 4.3 -(mu)m upper laser level, the degree of discharge excitation, and the presence of interfering absorptions. As a result, efficient operation is restricted to discharge pressures below 100 Torr and CO(,2) contents of less than 5 percent. The conditions which optimize performance are identified, and guidelines for scaling the 4.3-(mu)m laser to higher pulse energies are presented.