CO2-laser gas discharges in narrow gaps

We have studied RF discharges as excitation mechanisms for distributed feedback (DFB) CO₂ lasers. For CO₂ laser plasmas the reduced electric fieldE/N has to be in a well-defined range. The reduced electric fieldsE/N of gas discharges in the narrow gaps with widths of the order of 100 m required for DFB are considerably above this range. In order to study the feasibility of these RF-excited discharges for DFB CO₂ lasers we have measured the electron temperatureT _e in their plasmas. From helium-line-intensity ratios we have deduced a lower limit of the electron temperatureT _e of 4eV. The observed high intensities of bands of singly ionized nitrogen indicate an even higher electron temperature, but an efficient pumping of the upper laser level is not possible with an electron temperature above 2.5 eV.We have estimated the electron densityn _e and the current densityj _e from ratios of the intesities of forbidden and allowed helium lines. The high current densityj _e is in the range of abnormal glow discharges.In the gas discharges between narrow gaps the electron oscillation amplitudex _e is large than the electrode separationd. In order to replace the resulting high electron losses a high electron temperatureT _e is necessary to sustain the gas discharge. Because of this high electron temperatureT _e an efficient pumping of the upper laser level is not possible.     

The stability of the active medium of RF-exited CO2 lasers with gold as catalyst

Using mass-spectrometric investigations the gas composition of the active medium of sealed-off cw RF-excited CO₂ waveguide lasers have been studied. It has been found that a low degree of CO₂ dissociation and a laser power improvement can be achieved by means of a gold catalyst in the laser discharge volume. The conditions for long operational lifetimes of these lasers are described. Received: 21 December 1999 / Revised version: 1 May 2000 / Published online: 6 September 2000     

A hybrid unstable-waveguide resonator and output characteristics of a gap CO2-laser with high-frequency excitation

Experimentally and theoretically, we investigate the energy and spatial parameters of CO₂-laser generation with a gap active-medium geometry, high-frequency excitation, and an unstable-waveguide resonator. A generation power of 54 W is achieved in the continuous regime with the shape of the output radiation beam close to an axisymmetric one without resorting to external correcting optics. S. A. Esenin Ryazan State Pedagogical University, 46 Svoboda Str., Ryazan, 390000, Russia. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 6, pp. 784–790, November–December, 1999.     

Properties and current-voltage characteristics of discharges in waveguide gas lasers

The paper deals with the properties andI-V characteristics of discharges in narrow capillaries used, for example, for He−Ne waveguide lasers. It has been observed that discharges in He−Ne waveguide lasers are unstable because of the strongly falling characteristic. A theory is presented which assumes that at low currents wall charges restrict the positive column to a narrow plasma channel and are the main reason for the observed falling characteristic. A numerical evaluation for helium gives results which agree well with experimental data.     

Investigation of the active media in pulsed gas discharge lasers by the Rozhdestvenskii hook method

In this review we generalize the results of our experimental investigations in which the Rozhdestvenskii hook method was first used to look for an inverted population in new spectral transitions. An inverted population in new 3p–3s transitions of the neon atom with =588.1, 594.4, 650.6, and 653.2 nm was discovered in the active medium of a Penning plasma laser emitting the =585.3 nm neon line in Ne-H₂ and Ne-H₂-Ar mixtures. Results of investigations of a number of active media are given. An analysis is made of the spatial and temporal distributions of copper atoms in the ground state and of their influence on the lasing efficiency of a copper-vapor laser. Using the rhenium atom as an example, it was shown to be possible to obtain a sufficiently high concentration of refractory metal atoms (>10¹⁴ cm^–3) in an active medium to form active media of lasers utilizing self-terminating transitions and also plasma lasers.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 3–27, December, 1994.     

CO2 waveguide lasers with slab geometry

The research and design of 10 to 100-W RF-exited CO₂ lasers with slab geometry of the active medium and waveguide-unstable resonators are described. The power, the beam shape, and the radiation spectrum obtained in scanning of the laser head length are investigated. An unconventional method for mathing the RF power supply and the laser head is applied. Two models of compact 30-and 50-W lasers with an efficiency of 9% are described. The models presented can be recommended as basic designs for industrial production.Translated from Preprint No. 11 of the P. N. Lebedev Physical Institute, Russian Academy of Sciences, Moscow, 1995. 1071-2836/96/1701-0001$15.00     

Numerical modeling of active media of high-pressure group-II-metal lasers

Translated from a preprint (manucript) of the Lebedev Physics Institute, Russian Academy of Sciences, Moscow.     

Multiline laser probing of CO:He, CO:N2, and CO:O2 active media in a wide-aperture pulsed amplifier

Multiline laser probing was applied for the diagnostics of the active medium of a wide-aperture carbon monoxide laser amplifier. The temporal behavior of the small-signal gain in the active medium of a pulsed electron-beam sustained discharge CO laser amplifier was studied with a specially designed probe CO laser in a wide range of ro-vibrational spectral lines (from V = 5 up to V = 31). The results were analyzed in order to reconstruct the temporal behavior of gas temperature and vibrational populations in CO-containing gas mixtures, CO:He and CO:N₂, and oxygen-rich CO: O₂ mixtures. __________ Translated from Preprint No. 13 of the P. N. Lebedev Physical Institute, Moscow (2005).     

Tunable CW CO2 lasers with waveguide cavity

A laser that is tunable up to 1.6 GHz is described. A cavity with two selectors is described, capable of tuning the emission frequency in a band wider than the intermode distance. The gain in the laser active medium, including in CO₂ isotopes, is measured. Lasers with such parameters can be used in spectroscopy, photochemistry, and optical communication and ranging.Translated from Lazernye Sistemy, pp. 92–101, 1982.     

Effect of the active medium temperature on the operation of fast-flow CO2 lasers

A new formula is obtained for estimating the output power of fast-flow CO₂ lasers. It is shown that a higher specific output power of these CO₂ lasers in comparison with sealed-off CO₂ lasers is caused mainly by the higher saturation intensity of the former. It is concluded that the temperature of the laser active medium affects almost only the charge stability and that, under stable discharge conditions, the same output power can be obtained at different temperatures of the active medium.     

Wide-aperture CO2 lasers pumped with an electron-beam-controlled discharge

This review paper presents the results obtained during the development and study of three high-power wide-aperture CO ₂ lasers (λ=10.6 μm) pumped with a discharge controlled by an electron beam. In developing these lasers, the method of formation of a space discharge at elevated pressures due to uniform ionization of the working mixture by an electron beam with an energy of some hundreds of kiloelectron-volts was used, which was proposed by researchers at the Instute of High-Current Electronics (IHCE). Institute of High-Current Electronics, Siberian Division of the Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 5–11, April, 2000.