Specific features of the welding of metals by radiation of high-power fiber laser

The properties of the plasma that results from the laser welding of metals at various powers of the 10-kW ytterbium-doped fiber laser are experimentally studied. A projection system with an image intensifier based on a copper-vapor laser is employed for the direct observation of metal surface in the course of the laser welding in the presence of the high-intensity background illumination. A method for the shadow photographing is proposed for the analysis of the presence of metal vapor in plasma, since such vapor can lead to the reflection of the laser radiation in the course of welding.     

Investigation of a copper-vapor laser pumped by trains of damped sine pulses

A copper-vapor laser the lasing medium of which is pumped by damped sine voltage pulses is studied experimentally. It is shown that this laser can operate at megahertz lasing pulse repetition rates. Each current pulse in a train of damped sine excitation pulses generates a lasing pulse. The time between lasing pulses is no more than 224 ns, which corresponds to a lasing pulse repetition rate of more than 4.5 MHz. According to estimates, the use of the megahertz sine voltage to excite the copper-vapor laser may raise the specific power of laser radiation by at least an order of magnitude at an efficiency of ≈15%.     

Physical Simulation of Small bore Copper vapor Laser

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Enhanced performance of elemental copper-vapor lasers by use of H(2)-HCl-Ne buffer-gas mixtures

The output power from a 25-mm-diameter (volume, 0.49 L) and a 40-mm-diameter (volume, 1.9 L) copper-vapor laser (nominally 20- and 65-W devices, respectively) was approximately doubled to >50 and >100 W , respectively, by addition of small partial pressures of both H(2) and HCl to the neon buffer gas. The specific output powers of these lasers are believed to be records for any copper-vapor lasers of this size.     

Thermal lens and its effects in copper-vapor lasers

We have analyzed and measured the thermal lens of the copper-vapor laser by considering both its windows and active medium. The equivalent combined focal length varies with operation parameters and it is sensitive to the laser geometry. The results are verified by our measurements on a 20 W device with 35 mm internal diameter tube. The thermal lens effects on the beam properties are analyzed and verified with the experiments for both oscillator and laser chain case.     

Excitation efficiency of working transitions in copper-vapor lasers

The conditions under which the influence of the discharge circuitry inductance on the efficiency of pulsed-periodic copper-vapor lasers is weak are determined. It is shown that for efficient pumping of the lasing transitions of Cu atom in these lasers it is advisable to form an excitation pulse having steep edges of the voltage applied to the discharge tube with the duration spanning the pumping period and termination of the lasing process providing, at the same time, the conditions for aperiodic behavior of the discharge during the excitation pulse. Such a pumping pulse can be formed due to a partial discharge of the storage capacitor in the laser discharge circuit. It is also shown that under such conditions of excitation the efficiency of copper-vapor laser (CVL) with respect to the energy pumped into the active element can reach 10%.     

Kinetics of laser-induced Au pyrolytic deposition from the liquid phase

Kinetics of Au pyrolytic deposition from organic solutions of triphenyl phosphine complexes induced by a copper-vapor laser beam is studied experimentally. Activation energies T _a and pre-exponential factors are determined for 7 different Au complexes. Measured T _a values range from 1800 K to 9400 K. The average temperature of the GaAs wafer is found to be 70° C for a laser beam power of 10 mW.     

Modulation enhancement of a laser diode in an external cavity

The influence of Zn-atom additive on ‘pure’ copper vapor laser output characteristics is studied. The laser pulse width, energy and power are found to increase under the diffusion of zinc atoms from a zinc-containing reservoir into the discharge of the copper-vapor laser at temperatures above 500°C. Additional absorption experiments and calculations are consistent with the conclusion that not only optical resonant pumping by the 213.9-nm Zn I line, but also other processes, should be taken into account to explain the effects of additive influence.     

530-mW 7-kHz cerium LiCAF laser pumped by the sum-frequency-mixed output of a copper-vapor laser

We report, for what we believe to be the first time, a Ce:LiCAF laser pumped by ultraviolet radiation obtained by sum-frequency mixing of the green and the yellow output from a copper-vapor laser. The 7-kHz pulse repetition frequency free-lasing Ce:LiCAF laser yielded a maximum output power of 530 mW, with a slope efficiency of 32%, from a pump power of 1.9 W. With a single prism tunability from 280.5 to 316 nm was achieved.     

Method of two-pulse frequency regulation of copper-vapor laser parameters

A method for a wide-range control of the laser action parameters of a metal-vapor laser on self-limited transitions without violation of the heating regime is described. The method is based on the formation of an additional control pulse with each of the excitation pulses without laser action, and the regulation is realized by variation of the delay between the pulses. The method was tested with a copper-vapor laser. It is shown that the control of the lasing parameters is realized by changing the prepulse population of the metastable level of the active medium.     

Laser therapy of cancer patients

The results of using low-intensity copper-vapor laser radiation for patients already treated by conventional methods to prevent threatening postoperative and radiative complications are presented. The principal feasibility of using a copper vapor laser for treating precancer diseases is analyzed in a model of pretumor pathology of the stomach. Scientific Research Institute of Oncology of the Tomsk Scientific Center of the Russian Academy of Medical Sciences; Tomsk State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 109–118, August, 1999.     

Metal-vapor lasers with a high flow rate

The possibility of obtaining CW lasing on transitions between resonance and metastable levels in atoms of some metals is shown for the first time. In some cases, the conditions for obtaining lasing in these systems may be easier than those for the copper-vapor laser.     

Polarization and power characteristics of pulsed dye lasers with transverse pumping

Starting from the classical theory on molecular luminescence in liquids, rate equation for two-polarization-mode laser oscillation under transverse pumping with intense excitation have been set forth neglecting the influence of orientational relaxation of the dye molecules. Hence, the laser output power and polarization under different configurations have been obtained. The results show that the dye laser is partially polarized even when the pump beam is unpolarized and no polarizing elements exist in the cavity. If we define a reference plane consisting of the axes of the pump beam and the dye laser, the laser system has to adopt the plane perpendicular to the reference plane as the polarization direction in order to yield a highly efficient, linearly polarized laser output. Experiments on a copper-vapor laser pumped dye laser verified these analytical results.     

Outlook for parameters of CW copper-vapor lasers

Results of numerical experiments performed for a CW copper-vapor laser are presented. Calculations give an output power of about 15 W and a laser efficiency of the order of 0.1% relative to the discharge power. Strictly specified ranges of the main initial parameters are determined in which CW lasing is possible:p _Cu=0.26–0.69 mm Hg,p _Ne=0.4–1.2 mm Hg,E=40–125 V/cm.     

Phase diagrams of laser-processed nanoparticles of brass

Nanoparticles of brass are prepared by ablation of a brass target in ethanol using radiation of a copper-vapor laser at various laser fluences. The nanoparticles are characterized by TEM and optical spectroscopy. The multipulse laser irradiation leads to formation both the nanoparticles in liquid and well-ordered micro-structures on a surface of a target. It is revealed that both the morphology and absorption spectra of brass nanoparticles depend on presence of the micro-structures. Nanoparticles with the various phase diagrams are formed from a flat brass surface and from the same surface with micro-structures. The results are compared with a model of phase diagrams, in which size and composition effects are taken into account.     

Tunable narrow-band moderate-power laser system pumped by copper-vapor lasers

The construction of a narrow-band tunable dye laser system having a moderate power and pumped by copper-vapor lasers is proposed. The system consists of a master oscillator with a grating operating at grazing incidence, and a two-stage amplifier. The system is designed for laser isotope separation.     

Small-signal gain dependence on active medium length and axial thermal profile in metal-vapor lasers

We measure the small-signal gain coefficient g ₀ of a gold vapor laser for a 627.8 nm transition through the implementation of a discharge-driven oscillator-amplifier configuration. We study the gain dependence on the length of the laser active medium. In addition, we measure the output power of a copper-vapor laser for two different thermal insulator distributions and simulate the thermal-length profile to determine the effective length of the active medium. We show that the small-signal gain coefficient depends on the effective length of the active medium and do not depend on the physical (actual) length of the active medium.     

Generator on the basis of reversely switched dynistors forming pump pulses for a copper-vapor laser

A generator designed on the basis of reversely switched dynistors and forming pump pulses for a coppervapor laser is described. The operation of the circuit is considered in detail. Its main components are a low-voltage high-current switch operating on the basis of a reversely switched dynistor (RSD), a step-up pulse transformer, and a system for magnetic compression of pulses. It is shown that a RSD makes it possible to increase the efficiency and decrease the dimensions of the generator in comparison with thyristor systems. Pulses of electric current through the active element of a copper-vapor laser with a 40-ns leading edge and a repetition rate of 8 kHz are formed. Laser radiation with an output power of 2 W is obtained.     

Fast etching and metallization of SiC ceramics with copper-vapor-laser radiation

The etching of polycrystalline SiC is studied with the help of radiation of a copper-vapor laser either in air or under the layer of a liquid (H₂O, DMSO). The etching rate in air is as high as 0.24 m/pulse, in DMSO 0.07 gm/pulse at an energy density of 16 J/cm². The etched surface is characterized with Scanning Electron Microscopy (SEM) and X-ray diffractometry. Etching of SiC ceramics in air revealed the partial amorphization of SiC and the formation of microcrystals of elementary Si with an average size of 300 Å. The etched surface of SiC ceramics takes on the ability to reduce Cu from a corresponding electroless plating solution. The adherence of the deposit is as high as 30 N/mm² and is a function of the scanning velocity of the laser beam.