Comprehensive investigations of the lasing characteristics in the double-pulse regime, of the characteristics of excitation pulses, and of the decay of metastable active levels during the discharge afterglow were made using a copper vapor laser with a 12-mm diameter 40-cm long discharge tube and operating in the self-heating regime. It was found that under conditions close to efficient lasing, the recovery of the lasing ability during the second pulse was mainly determined by the decay of the metastable levels.

Decay of metastable states and its influence on the lasing characteristics of a copper vapor laser

A study was made of the spatial kinetics of the decay of metastable atoms, resolved over the radius of a copper vapor gas discharge tube, under conditions typical of the self-heating regime. The investigations were carried out for a time interval of 1–100μsec after the excitation pulse, with a radial resolution of 2–3 mm, in the entire lasing temperature range. A profile of the population of the metastable states having a minimum on the axis transformed into a profile with a maximum on the discharge axis during the interpulse time interval. An analysis was made of the possible processes during the afterglow of the discharge and estimates were obtained of the electron density and temperature in the laser plasma.

Relaxation of metastable atoms during the afterglow in a copper vapor laser

Depletion of the metal vapor density from the central region of metal vapor laser tubes has recently been identified as an important factor limiting laser output. We have studied the mechanisms that deplete the ground-state metal density profile by measuring radially resolved population histories of neutral and ionic species during a “burst” (i.e., a pulse train of 20–30 excitation pulses) in a barium vapor laser (BVL). The observed spatiotemporal density behavior during the afterglow of the first shot in the burst agrees well with a simple model for diffusion and recombination, which we have used to show that the primary depletion mechanism during the establishment of steady-state conditions arises from the ambipolar diffusion of ions to the tube wall, and that gas-heating effects are secondary. Analysis of the steady-state (i.e., late-burst) afterglow behavior further reveals that the depletion is significantly greater than that expected from the measured barium ionization, particularly when operating a...

Ground-state depletion mechanisms in pulsed barium vapor lasers

Pulsed metal vapour lasers (PMVLs), utilising transitions from resonance to metastable levels in atoms and atomic ions (r-m lasers), especially copper vapour laser (CVL), are now among the most efficient and powerful gas lasers in the visible and near IR regions of spectrum. They are widely used in many important applications. Consequently, they were subject of many investigations. Nevertheless, understanding of basic kinetic processes controlling operation of these lasers is still not satisfactory. As the result it is difficult to predict attainable output power, efficiency and other characteristics of the lasers. This is a result of considerable experimental difficulties associated with experimental investigations of kinetics in PMVL.

Kinetics of Metal Vapour and Metal Halide Lasers

The paper presents the results of the research and development of the CuBr laser with continuous control of each pulse energy. The prototype consists of a large volume CuBr active element with an unstable cavity, two high voltage pulses generators and control system. The HBr additive was used to increase the laser energy-frequency characteristics. Control of laser pulses energy has been provided by high-voltage preionization pulses. The linear control of output power from 5 W to 0 have been demonstrated. The metastable atom population is the major factor in the energy control. The dependence of the preionization pulse energy for full suppression on the active media operating mode (CuBr concentration, pumping energy etc.) was studied. The ratio between excitation pulse energy and preionization pulse energy for full suppression of the lasing changing from 18 to 25.

Continuous control of CuBr laser pulse energy

The method of resonance absorption of the 510.6 nm line was used to determine the density n/sub m/ of the 4s/sup 2/ /sup 2/D/sub 5//sub ///sub 2/ metastable level of the copper atoms during the interpulse periods of a Cu laser, in the neon buffer gas pressure range of 10--50 kPa. At pressures exceeding 10 kPa an increase in n/sub m/ was observed (following rapid decay) over a period 5--10 ..mu..sec after the current pulse. A numerical solution of the problem of relaxation of the plasma parameters showed that the complex nature of the variation in n/sub m/ can be explained by a combination of a number of processes including recovery of the concentration of the copper atoms in the ground state and relaxation of the temperature and density of the electrons.

Relaxation of the 4s2 2D5/2 metastable level of the copper atom in the afterglow of a pulsed discharge in a copper vapor laser

An investigation was made of the radial profiles and temporal relaxation of metastable copper atoms during the interpulse period in a self-heated copper vapor laser. The copper atom concentration in the ground state and the electron temperature, together with their radial profiles and time dependences, were determined from the experimental data. In a copper vapor laser with a 2-cm gas discharge-tube diameter the conditions were sometimes characterized by the presence of a radial electron temperature gradient and also a steady-state distribution of the copper atoms differing from the equilibrium distribution by a deficiency of copper atoms on the axis which arose due to an insufficiently high rate of diffusion of the copper atoms to the central zone from the periphery.

V Yu Fuchko

Papers

Relaxation of the 4s2 2D5/2 metastable level of the copper atom in the afterglow of a pulsed discharge in a copper vapor laser

Radial inhomogeneities of the active medium plasma parameters in a self-heated copper vapor laser during the interpulse period