Krasimir A. Temelkov

Determination of characteristic constants for some basic processes in plasma?diffusion, Penning ionization, asymmetric charge transfer

The diffusion coefficients of ten chemical element atoms in the binary system with helium and neon are calculated on the basis of 12-6 Lennard-Jones and rigid sphere inter-atomic interaction approximations. Cross-sections and rate constants for thermal energy charge transfer and Penning collisions are calculated for all Tl+ and I+ excited states possibly populated via these reactions. For the case of the charge transfer process the theoretical results are compared with the experimentally obtained ones. Since the characteristic constants considered depend on the gas temperature, the gas temperature distribution is also calculated by solving the heat conduction equation for the gas discharges studied.

Laser grade CaF2 with controllable properties: growing conditions and structural imperfection

Optical properties of CaF2, grown by a controlled Bridgman–Stockbarger technique, are studied by CuBr and SrBr2 vapour lasers. Absorption losses are determined as a function of the grown crystal volume, the crystallization front (CF), and the real crystallization rate. It is found that the absorption losses are relatively independent of the transmitted wavelengths in a wide spectral range from the deep ultraviolet (DUV) to the middle infrared (MIR) spectral region and their minimum corresponds to CF positions within the upper half of the adiabatic furnace zone, where the CR reaches a constant value slightly higher than the speed of crucible movement. The crystal quality conforms to laser grade CaF2 for the DUV, visible and MIR spectral regions and may be controlled efficiently by introducing an appropriate systematic correction in the furnace temperature field, which shifts the CF position.

Temperature Model of a New High‐powered SrBr2 Laser

The radial temperature in the cross‐section of a strontium copper bromide vapor laser is studied on the basis of a previously constructed mathematical model. The model has been expanded so as to allow for changes to the structural elements of the tube, in order to develop a new laser with an increased power output. The limits of the maximum allowed operating temperature of the gas have been established. The numerical results of the simulations have been presented.

Temperature scaling of a Sr+ recombination laser

Water-cooled stable operating at average powers of 0.6-1.1 W, Sr+ recombination laser with independent production of Sr vapor is reported. Some features of the discharge tube construction and the laser operation are given. It is found that the application of the water cooling enables a higher input power loading for optimum tube-wall temperature. At Sr+ laser with independent production of the metal vapor it is possible to control the concentration of the Sr vapor and to inhibit the effect of overheating on lasing. This peculiarities result in an increase in the average laser power and an improvement of the laser operation stability.

Analytical Model of the Temperature in UV Cu+ CuBr Laser

In this study, a new analytical model for computing the temperature profile in the cross‐section of the tube in ultraviolet copper ion excited copper bromide laser is developed. The model is based on the solution of the two‐dimensional heat conduction equation under the boundary conditions of the third and fourth kind. Temperature profiles of natural convection are obtained, taking into account the basic laser design parameters, temperature insulation of the tube and the input electric power. Different engineering solutions for effective control of the discharge temperature are proposed and numerically investigated.

Comparative investigation on the output characteristics and electrical parameters of the UV Cu+ Ne-CuBr laser excited by the Blumlein and IC excitation schemes

A comparative investigation on the output characteristics and the electrical parameters of the UV Cu+ Ne-CuBr laser excited by the Blumlein and IC excitation schemes is reported. An optimization of the UV multiline average output power with respect to the discharge conditions is carried out for both excitation schemes. It is obtained that the use of the IC excitation scheme leads to a 30% increase of the average output power at a simultaneous lasing on the five Cu+ lines- 248.6, 252.9, 259.7, 260.0 and 270.3 nm, in comparison with the Blumlein scheme. A two-longitudinal-mode oscillation (TEM00 and TEM10 is obtained on the 248.6-nm Cu+ laser line with an average output power of 25 mW. When a Ne/He gas mixture (He pressure - 8 Torr and total pressure - 21.7 Torr) is used, a simultaneous laser osciallation on the 248.6-nm and 780.1-nm Cu+ laser lines is also obtained with equal average laser powers of about 30 mW.

A new laser tube construction for the UV Cu+ Ne-CuBr laser

An experimental study on a new laser tube construction for the UV Cu+ Ne-CuBr laser, conformable to our previous investigation on the reasons leading to a reduction of the tube lifetime, is reported. An optimization of the UV multilane average output power with respect to the discharge condition is presented. Laser tube lifetime up to 180 hours at an average laser power of about 700 mW is also reported.

Kinetic and experimental study on the influence of the inside tube diameter on the UV ion Ne-CuBr laser output parameters

A simplified model, describing the kinetic processes in a nanosecond pulsed longitudinal Ne-CuBr discharge afterglow, is made. It is shown that the influence of the active zone diameter decrease on the inversion population and hence on the output power and the laser pulse on the 248.6 nm line is due to the more effective population of the upper laser level, because of the higher neon ion density and mainly because of the more effective depopulation of the lower laser level. Optimal discharge conditions for UV laser operation are found for different active zone diameters of the laser tube - 12 mm, 9.5 mm, 9 mm, 8 mm, 5.8 mm, 5.7 mm, 5.2 mm and 4 mm. With diameter reduction a record average laser power of 1.3 W is obtained at multiline output. The highest peak pulse and average output powers are measured on the 248.6-nm laser line for the UV Cu+I lasers - 3.25 W and 0.85 W, respectively. The obtained specific average laser power is 56.6 mW.cm-3 at an active volume of 23 cm3.

Copper ion laser in He-CuBr, He-Cu, and Ne-CuBr pulse longitudinal discharge

In ns-putsed longitudinal discharge-excited He-Cu and He-CuBr vapor ion lasers oscillation in the IR spectral range has been obthined. UV laser operation has been obtained only in Ne-CuBr vapor ion laser. An average output power of 210 mW has been measured on the laser line 248.6 nm and a 270 mW on multiline - 248.6, 252.9, 260.0 and 270.3 nm.

Theoretical and experimental study of some basic processes in He-TlI and Ne-TlI plasma - asymmetric charge transfer, penning ionization and diffusion

The diffusion coefficients of thallium and iodine atoms in a binary system with helium and neon are calculated on the basis of 12-6 Lenard-Jones and rigid sphere models. Cross-sections and rate constants for thermal energy charge transfer into some Tl+ and I+ excited states are theoretically and experimentally obtained for a gas discharge in He-TlI and Ne-TlI mixtures. Cross-sections and rate constants for Penning ionization into Tl+ and I+ ground and excited states are calculated for Penning collisions with the He and Ne metastable atoms. Since the characteristic constants studied depend on the gas temperature, the radial gas temperature distribution is also calculated through solving the heat conduction equation.