Au-II 282 nm segmented hollow-cathode laser-parametric studies and modeling

Abstract

Laser operation on the Au-II 282.3 nm ultraviolet transition is obtained using a high-voltage segmented hollow-cathode discharge tube. The metal vapor is produced by means of cathode sputtering. A small amount of argon is added to the helium buffer gas in order to achieve higher sputtering yield. Measurements of the laser power and small signal gain indicate that the optimal partial concentration of argon is in the range of 0.25%-0.75%. Quasi-continuous wave output power of 100 mW is obtained from a 34-cm-long active region while the highest small-signal gain is 52% m Ϫ1. To explain the basic features of the laser operation we present a model of the segmented hollow-cathode discharge. All the discharge characteristics are calculated in a self-consistent way except the temperature of slow electrons. The trajectories of fast electrons emitted from the cathode are followed by Monte Carlo simulation. Rate equations of ion, metastable and metal atom densities are solved in the negative glow, while another Monte Carlo code is applied for the fast heavy particles in the cathode sheath. The spatial distribution of the gas temperature and the thermalization of sputtered metal atoms are calculated as well. The laser characteristics predicted by the model are in reasonable agreement with the experimental results.

On the accuracy and limitations of fluid models of the cathode region of dc glow discharges

“…The advantages of fluid models (efficiency) and of particle treatment (accuracy) can be jointly utilized in hybrid models [11], in which slow plasma species are treated within the frame of a fluid model, while fast species (in particular fast electrons, which drive ionization and excitation reactions) are treated as particles [12][13][14][15]. Although one needs to be aware of their limitations [16], hybrid models have been very successful in describing a wide range of discharge physics phenomena and providing deep insight into the operation of different discharge configurations, such as pseudospark switches [12], analytical glow discharge cells [17] and hollow cathode discharges for gas lasers [18,19].…”

molecular ions in helium glow discharges: the effect of bulk electron temperature

“…In some previous investigations on lowpressure negative glow discharges, cold electron temperatures significantly lower than 1 eV have been found. These studies include the laser based diagnostics of Den Hartog et al [17], theoretical calculations of Arslanbekov and Kudryavtsev [18], Langmuir probe measurement of Bogaerts et al [19], Angstadt et al [20] and Ohsawa et al [21], Thomson scattering measurements of Gamez et al [22] and experimental investigations of hollow cathode discharges by Warner [23], Leigh [24] and Bánó et al [25]. In all these works cold electron temperatures ranging between 0.08 and 0.5 eV have been found.…”

On the reliability of low-pressure dc glow discharge modelling

“…Using these techniques, previous experimental investigations on low pressure negative glow discharges usually resulted in cold electron temperatures significantly lower than 1 eV. These studies include laser based plasma diagnostics [54], Langmuir probe measurement [55][56][57], Thomson scattering measurements [58] as well as spectroscopic investigations of hollow cathode discharges [59]. In all these works cold electron temperatures ranging between 0.08 and 0.4 eV have been found.…”