Academic and Research Staff A. Time -dependent Characteristics of Pulsed Ion Lasers

Our general objectives are concerned with the study of atomic and molecular processes and with the transport of charged particles in weakly ionized collision-dominated plasmas. We are devoting our efforts to those problems in gaseous electronics that are relevant to the physics of gas lasers. These devices have numerous applications. We are expanding our studies of gas lasers to the development of techniques for measuring gas-discharge parameters such as collision cross sections as a function of energy, by using the lasing mechanism as a probe. In particular, we are investigating the observed time delay between the beginning of the excitation current and the output laser pulse. It is thought that this delay is a measure of the excitation cross section. These delays have been seen in both ion and He-Ne lasers. We have recently developed a theory for extending the useful range of microwave cavities for obtaining electron densities by cavity frequency shifts. This technique is being used in the studies of ion lasers both in the pulsed and cw regimes. With the advent of the high-pressure CO 2 laser our attention has been focused on studying the plasma formation. At present, the power output of these lasers is limited because the plasma is extremely nonuniform; only a few per cent of the gas medium is actually excited. We are also looking into problems of striations, sound propagation, and mode locking, which have practical applications in producing better and more stable gas laser devices.