A computer model of a transverse discharge cw CO laser

A kinetic model has been developed for the investigation of the novel performance of a CO laser, on which efficient extraction of laser power was obtained by exciting a subsonic gas mixture of CO/N₂/He/O₂ through transverse dc discharge. Kinetic equations for direct excitation by electron impact, V-V and V-R/T energy transfer, and stimulated emission are coupled with a semi-one-dimensional flow model. Careful consideration is devoted especially to the V-V transfer process of CO–N₂ and N₂–N₂. The laser power was calculated by a constant gain method. The laser output performance, examined as a function of gas mixture ratio, temperature, flow velocity, and discharge current, was in good agreement with the experiment.     

Performance studies of a pulsed HF laser with a sliding discharge plasma cathode

The plasma electrode design concept is applied for the first time to an HF laser. The discharge along the surface of a dielectric (sliding discharge) is used as a plasma cathode for the main laser discharge. The laser operates at atmospheric pressure with a gas mixture of He/SF₆/C₃H₈. Details are presented on the efficiency of energy transfer, the dependence of laser performance on circuit parameters, gas mixture, relative energy loading and time delay between the plasma electrode and main discharges. The F atom production rate is estimated from the linear dependence of the output energy on the electric charge passed through the discharge. Output energies of 600 mJ were obtained at 1.6% efficiency from a small active discharge of 108 cm₃ volume and 38 cm length, while the maximum specific input and output energies were 370 J/1 and 5.7 J/1, respectively. These values compare favourably with those reported in the literature for non-chain-reaction-type gas mixtures at 1 atm pressure and demonstrate that the plasma electrode design is a powerful scheme for developing gas-discharge lasers.     

Detailed vibrational population distributions in a CO2 laser discharge as measured with a tunable diode laser

A tunable diode laser (TDL) operating in the 2150–2350 cm^–1 wavenumber region is used to probe a conventional cw CO₂ laser discharge. Absorption lines in more than 25 different vibrational bands are observed, enabling us to determine absolute vibrational populations inall levels of concern to the dynamics of the 10 m CO₂ laser. Levels in thev ₃ mode of CO₂ as high as 00°9 are monitored, and it is found that anharmonic effects play a significant role in the populations of such levels. Thev ₁ andv ₂ mode populations are also investigated in detail, and it is found that these modes are strongly coupled and maintain a common vibrational temperature under all discharge conditions. The use of a TDL is shown to be a powerful technique for investigating the dynamics of infrared molecular lasers.This work was supported in part by the National Science and Engineering Research Council, Canada     

A magnetically stabilized coaxial laser discharge

A new magnetic discharge stabilization technique for coaxial laser systems is described. The approach utilizes crosses electric and magnetic fields to create and maintain a large and rapidly rotating plasma volume which does not experience glow-to-arc transitions. Very high cw specific discharge power loadings have been achieved even without the benefit of external gas cooling or circulation.Performance is insensitive to gas composition and pressure such that high power coaxial discharges have been run in CO₂ laser gas mixtures up to several hundred torr. Stable cw discharges have also been obtained in mixtures containing several torr of SF₆.The technique appears to be readily scalable to give very large excited volumes in systems with comparatively small overall physical dimensions.     

Gain and saturation measurements in a discharge excited F2 laser using an oscillator amplifier configuration

The small-signal gain coefficient and the saturation intensity of a F₂ pulsed discharge molecular laser at 157 nm have been measured using two discharge devices in an oscillator-amplifier configuration. The small signal gain coefficient was measured to be 5.2±0.4% cm^–1 at 3 atm total pressure and 1.5 cm electrode spacing and 4.1±0.4% cm^–1 at 2 atm total pressure and 2 cm electrode spacing while the values of the saturation intensity were 5 MW/cm² and 4.6 MW/cm², respectively.     

Numerical simulation of gas flow in a magnetically stabilized coaxial laser discharge

The neutral gas flow profile within a magnetically stabilized coaxial laser gas discharge is analyzed by using a single fluid magnetogasdynamic model. Equations describing the rotational, radial and axial gas transport are solved by using an iterative alternating direction implicit method. Steady state rotational velocities of the order of 20 m/s are found.     

Characteristics of an x-ray preionized TEA CO laser

A cryogenically cooled sealed-off x-ray preionized self-sustained discharge CO laser was succesfully operated. It was found that 20 to 40% higher output energies could be obtained using x-ray instead of uv preionization. A maximum output energy of 2.9 J per pulse could be extracted from a 2×2×40cm³ discharge volume. The maximum electrical efficiency proved to be 12.6%.     

Multiple harmonic conversion of pulsed CO2 laser radiation in Tl3AsSe3

The nonlinear material Tl₃AsSe₃ is used to convert pulsed 9.6 m CO₂ laser radiation into its second, third, fourth and fifth harmonic. Internal (external) conversion efficiencies of 28, 14(6.7), 3.6(3.1), and 0.5(0.3)% from the pump fundamental are achieved in 4.8, 3.2, 2.4, and 1.9 m generation respectively.     

High-efficiency,high-energy performance of a pulsed HF laser pumped by phototriggered discharge

A comparison of the performance of pulsed infrared HF lasers pumped by phototriggered discharges using either Ne/SF₆/H₂ or Ne/SF₆/C₂H₆ mixtures are presented. For an active volume of 50 cm³, a specific output energy as high as 11 J/ has been achieved with an efficiency higher than 3% when C₂H₆ is used as H atom fuel. The replacement of ethane by molecular hydrogen reduces the laser performance by 40%. The investigation of the temporal evolution of the laser intensity shows that this dramatic decrease results from a shortening of the laser pulse duration rather than from a decrease of the peak power. Indications are given that this behavior is correlated to a very different temporal evolution of the discharge parameters, especially at low reduced electric field E/N.     

Mode selection in an unstable-resonator TEA CO2 laser by injection from a waveguide laser

The effect of injecting radiation from a cw waveguide CO₂ laser into a TEA laser through a hole in one mirror of its unstable resonator has been studied experimentally. High-power single longitudinal mode operation of the TEA laser is achieved over a wide but finite range of injection frequencies, the frequency of the single-mode pulse being that of the TEA laser cavity mode lying closest to the injected frequency. Although a simple theoretical model shows good qualitative agreement with observations it underestimates the range of injection frequencies which result in single-mode pulses unless a fast chirping of the cavity mode frequency is postulated.     

New FIR laser lines from CHD2OH optically pumped by a cw CO2 laser

This work reports 83 new optically pumped far infrared laser lines, using deuterated methyl alcohol, CHD₂OH, as active medium. For each line we list the measured wavelength, its polarization relative to the pump line, the optimum gas pressure and the CO₂ laser pump power at the maximum absorption.     

Tunable simultaneous double-wavelength operation of a cw CO2 laser

Stable step-tunable simultaneous double-wavelength emission from any branch combination of the 9.6 and 10.6 μm bands of a cw CO₂ laser is reported in which the relative strengths of the two signals may be controlled.     

High-pressure behaviour of an X-ray preionized discharge pumped XeCl laser

The output characteristics are described of an X-ray preionized discharge pumped XeCl laser, fed by a low-impedance pulse forming line (PFL), at pressures up to 12 bar. The influence of a multichannel rail gap placed between the PFL and the laser head on the output energy was studied. We found an increase of output energy with increasing pressure up to 8 bar. At higher pressures a saturation behaviour was found. The maximum output energy per unit volume was 6.5 J/l.     

CO laser stabilization using the optogalvanic Lamb-dip

Frequency stabilization of the CO laser using a CO lamb-dip is achieved in the range from 5.0–6.3 m. The CO saturation signal is obtained from a low-pressure discharge in absorption and is detected using optogalvanic, detection. The frequency stability and reproducibility has been verified to be better than 100 kHz; this is an improvement of more than one order of magnitude compared with locking techniques using CO laser gain profiles.Alexander von Humboldt Awardee from National Bureau of Standards, Boulder, Colorado, USA     

Comparative study of spectral narrowing of a pulsed Ti:Sapphire laser using pulsed and CW injection seeding

We report a comparative study of a pulsed as well as continuous-wave (cw) injection seeding of a Ti:Sapphire laser pumped by aQ-switched frequency-doubled Nd³⁺:YAG laser for achieving narrow spectral bandwidth. The results have indicated that the Ti:Sapphire laser using either a pulsed or a cw injection seeding could achieve efficient energy extraction in a narrow spectral bandwidth. In the case of pulsed injection seeding, the injection energy required for the complete injection seeding critically depended upon the timing of the Ti:Sapphire laser with respect to the delayed onset of the slave laser. On the other hand, in the case of cw injection seeding, the spectral bandwidth of the Ti:Sapphire laser was efficiently narrowed down to approximately 0.01 cm^–1 with an injection power of less than 1 mW. In both types of injection seeding, characteristics observed experimentally were compared with those obtained by a numerical simulation code based on the one-dimensional rate-equation model.     

New cw fir laser emissions from CO2 laser-pumped vinyl bromide

47 new cw far-infrared laser lines with wavelenths between 453 and 2356 m have been obtained by optically pumping vinyl bromide (C₂H₃Br) by a CO₂ laser. A significant portion of these lines has wavelengths longer than 750 m.     

New FIR laser lines from CD3OD optically pumped by a CO2 waveguide laser

In this work we report new FIR laser lines from CD₃OD optically pumped by a CO₂ waveguide laser. The wide tunability of this laser (290 MHz) makes it possible to pump absorption lines with large frequency offset relative to the CO₂ laser line center, which are not possible by using conventional CO₂ lasers. As a consequence 19 new laser lines have been discovered, ranging from 38.0 m to 455.2 m in wavelength. For all lines, precise frequency offset measurements between the CO₂ line center and the center of the absorber CD₃OD line were performed using the transferred Lamb-dip technique. We also present direct Doppler-free offset measurements of infrared absorption, obtained within the FIR laser cavity itself, using optoacoustic detection.Work supported by FAPESP, CNPq, FAP-Brasil and CNR-Italy     

X-ray preionized CO2 laser

A short pulse (100 ns) high-energy x-ray source has been used to preionize a transversely excited carbon dioxide gas discharge laser of 600 cm³ active volume. The maximum output power of 60 MW in a 50 ns FWHM pulse was achieved from a CO₂–N₂–He–CO–Xe static gas mixture at 600 Torr pressure. The energy conversion efficiency was 6%.