Intrinsic Efficiency and Critical Power Deposition in the e-Beam Sustained Ar:Xe Laser

Experimental investigations on an e-beam sustained near infrared Ar :Xe laser have been carried out to determine the intrinsic efficiency at optimized conditions. A parametric study at different sustainer currents reveals a maximum output energy depending on current density. Up to 8 bar the optimized laser output power per unit volume increases linearly with 1.1 M W / l b a r . Intrinsic efficiencies of up to about 8% are feasible. PACS: 42.55 Fn, 41.80 Dd, 52.80 Tn The near infrared A r : X e laser has attracted much interest because this type of laser shows a high intrinsic efficiency and a high specific energy. It uses rare gases for the active medium resulting in a long gas lifetime. The wavelengths due to transitions between the 5d and 6p levels of Xe are between 1.73 and 3.51 gm and are short compared to that of a CO2 laser. There is no gas dissociation and no thermal population of the lower laser level so that cooling provisions are less critical. In this paper results will be presented from measurements on an e-beam sustained electrical discharge Ar :Xe laser. This technique has been successfully applied in the past for excimer laser studies [1] and for the Ar :Xe laser [2~4]. It uses the e-beam both to ionize the medium and to maintain the stability of the discharge. The sustainer discharge ionizes the xenon atoms again from the metastable (6s) state. In this way the system works as a four-level system with the metastable state as the ground state in the excitation scheme. The e-beam excitation from the atomic ground state assures sufficient replenishment for metastable atoms that are quenched to the ground state. In the present studies we investigated the opt imum conditions with respect to efficiency and laser output as a function of experimental parameters such as gas pressure and current densities of e-beam and sustainer. 1. Experimental Configuration The experiments are carried out using an e-beam sustained electrical discharge laser head. A cross-sectional view of the laser is given in Fig. 1. The e-beam enters the active volume through a 5 x 55 cm 2 window made of a 25 gm titanium foil supported by a Hibachi structure. We used in our studies two different e-beam parameters. One e-beam has a peak electron energy of 90 keV, a maximum current density of 40 m A / c m 2 and a pulse duration of 0.8 gs after passing the foil. The other one has a peak energy of 180keV, a current density of 120mA/cm 2 and Fig. 1. Cross-section of the laser head