The method of manufacturing and the results of studies of a lens corrector that converts a spherical diverging front into a plane one and is intended for studying flat surfaces as part of an interferometer with a diffraction comparison wave is described. A feature of the corrector is the use of an aspherical convex surface with a maximum deviation of 200 μm from the nearest sphere. The first experimental results are presented, indicating the prospects for using ion-beam processing to improve the quality of the wavefront. After the procedure of ion-beam processing, the aberrations over the entire aperture of the corrector decreased by more than 4 times and amounted to the parameter of the height difference PV = 207 nm ( λ/3) and (RMS) = 19.2 nm ( λ/33). On an area with a diameter of 80

A short external cavity (EC) providing a single frequency lasing of quantum-well diode lasers with broad optical gain profiles has been developed. A feature of the proposed EC is the use of a resonant reflector formed by two thin (with thickness of approximately 100 µm) cover glasses as a return mirror. The HL8338MG laser equipped with a similar short EC made it possible to demonstrate the continuous optical frequency tuning within 100 GHz and discrete wavelength tuning in the 12.3 nm range with an output power of approximately 20 mW. The applicability of such a tunable diode laser source for gas spectroscopy was confirmed by the observation of three krypton absorption lines near 829 nm in a low-pressure radio frequency discharge.

As one of the methods for decreasing toxic nitrogen oxide NOx pollution due to fuel–air mixture burning, the method for NO conversion to NO2 in dielectric barrier discharge plasma is currently proposed. The results of NO2 and О3 concentration measurements at the barrier discharge output in dry air depending on the discharge power and methane content in the mixture are presented. The threshold electric power of the discharge, the exceeding of which causes NO2 formation, is measured as 46.5 ± 0.5 W. It is found that a СН4 addition enhances NO oxidation to NO2.

— The rate constants of the Ar 2 p 6 , 2 p 7 , 2 p 8 , and 2 p 9 state quenching during collisions with helium in Ar/He plasma were obtained for the first time at a gas temperature in the discharge plasma of ~410 K. Ar/He plasma is an active medium convenient for studying optically pumped lasers based on metastable atoms of heavy inert gases. Previous models did not contain the 2 p 6 and 2 p 7 levels, but they should be taken into account in double pumping schemes. Experiments show that these levels are actively populated at pressures above 100 Torr. The rate constants are determined by simulating the time dependences of the 2 p 6 , 2 p 7 , 2 p 8 , and 2 p 9 concentrations obtained experimentally by pumping the 1 s 5 → 2 p 7 and 1 s 5 → 2 p s transition using radiation of a pulsed tunable Ti:Sa laser.

Abstract—Collisional broadenings and shifts of argon lines at 811.5 nm and 912.3 nm relevant to the lasing cycle of an optically pumped rare gas laser (OPRGL) are calculated. The calculations are based on the Lindholm–Foley theory and van-der-Waals potential. The results allowed estimation of the validity of previously measured broadening and shift coefficients of these Ar lines in pure gas and Ar–Ne mixture.

Results of simultaneous measurements of pressure shift beta and broadening xi coefficients for 912.3 nm Ar and 703.2 nm Ne spectral lines of the (n+1)s[3/2](2) -> (n+1)p[1/2](1) transition are presented. This is a lasing transition in a recently proposed optically pumped rare gas laser. Absorption line shapes fitted to Voigt profiles permitted to assess gas temperature by determining Doppler width components. These coefficients for the Ar 912.3 nm line with He and Ne as the collisional partners were determined for the first time. The values of shift and broadening coefficients in units of 10(-10) s(-1) cm(3), reduced to 300 K are: beta(Ar-Ar) = -2.11 +/- 0.05, beta(Ar-Ne) = -1.21 +/- 0.05, beta(Ar-He) = 0.37 +/- 0.03, beta(Ne-Ne) = -0.78 +/- 0.05, beta(Ne-He) = 0.0 +/- 0.05; xi(Ar-Ar) = 2.8 +/- 0.1, xi(Ar-Ne) = 1.68 +/- 0.05, xi(Ar-He) = 3.7 +/- 0.1, xi(Ne-Ne) = 1.94 +/- 0.05, xi(Ne-He) = 3.18 +/- 0.05. (C) 2022 Elsevier Ltd. All rights reserved.

The dependence of pumping thresholds of the optically pumped Ne*-He laser on the position of the pump beam between the electrodes was obtained for $\mathrm{s}_{5}\rightarrow \mathrm{p}_{9}$ or $\mathrm{s}_{5}\rightarrow$ p 8 pumping transitions. It was found that pumping thresholds strongly depended on the position of the pumping beam, and the minimum is reached near the center between the electrodes. The ratio of p 8 /p 9 thresholds at their minima is 13.

The method of manufacturing and the results of studies of a lens corrector that converts a spherical diverging front into a plane one and is intended for studying flat surfaces as part of an interferometer with a diffraction comparison wave is described. A feature of the corrector is the use of an aspherical convex surface with a maximum deviation of ∼200 μm from the nearest sphere. The first experimental results are presented, indicating the prospects for using ion-beam processing to improve the quality of the wavefront. After the procedure of ion-beam processing, the aberrations over the entire aperture of the corrector decreased by more than 4 times and amounted to the parameter of the height difference PV = 207 nm (∼λ/3) and RMS = 19.2 nm (∼λ /33). On an area with a diameter of 80%, the aberrations fell to the nanometer level: PV = 65 nm (∼λ/10) and RMS = 8.3 nm (∼λ/76).

Optically pumped rare gas lasers (OPRGL) suggested recently as a chemically inert analog of diode-pumped alkali lasers are under extensive study at present. OPRGLs employ metastable atoms of heavier rare gases (Rg*) in He bath produced in discharge plasma. Ar* OPRGL is the most popular system at present, due to presence of a narrow band diode pump and abundance of Ar. However, Ne* OPRGL is interesting due to its visible lasing wavelength at 703.2 nm nm and presence of channels of energy transfer in Ne-He plasma that facilitate Ne* production. We present the first results of experiments with Ne* OPRGL that include Ne* number density in its active medium, and lasing experiments to determine pumping threshold for s5 → p9 transition in a transverse pumping configuration using a narrow band pulsed dye laser as a pump.

Measurements of pressure broadening and shift coefficients for 640.2 nm Ne line were performed in an RF discharge without stabilization of neutral gas temperature. A diode laser with a short external cavity was used for metastable neon absorption spectroscopy in a natural mixture of neon isotopes. An appropriate fit function was constructed permitting deduction of Doppler and Lorentz components for the Voigt profile of the spectral line. To determine pressure broadening xi and shift beta coefficients for pure Ne and Ne:He mixture we used the information about Lorentz linewidth, position of the line center and gas temperature derived from spectral line shape fitted to a model line profile. The values of the collisional coefficients reduced to 300 K in units of 10(-10) s(-1) cm(3), are xi(Ne-Ne )= (1.9 +/- 0.2), xi(Ne-He) = (3.4 +/- 0.2); beta(Ne-Ne) = -(0.7 +/- 0.1), beta(Ne-He) = (0.13 +/- 0.04). (C) 2020 Elsevier Ltd. All rights reserved.

Optically pumped rare gas lasers have the potential for scaling to high-power cw systems with good beam quality. Metastable atoms of heavier rare gases that are the lasing species are produced in an electric discharge at near atmospheric pressure. The key problem for this class of lasers at present is the development of a suitable discharge system. In this paper, we present the results of optimization of a pulsed discharge system with the goal of minimizing cathode sputtering and peak discharge current. The first demonstration of a transversely pumped system and measurements of the optical pumping threshold for the Ar:He laser are also presented.

A diode laser configuration with a short external cavity in which an additional reflector is formed by a packet of two thin cover glasses is proposed. The use of such external cavities in combination with diode lasers based on quantum-well heterostructures is promising for Doppler broadening spectroscopy and the cases where a wide range of continuous tuning at moderate requirements for the laser linewidth is important.

A calibrating apparatus for spectrometers of the red and near infrared bands based on the analysis of the emission spectra of inert gases is described. One feature of this calibrator is the use of readily available starters for fluorescent lamps as optical emitters. A radio-frequency discharge was used to excite gases in the starters. Starter models (with neon and argon) were selected that made it possible to cover the important spectral band for diode lasers (600–1400 nm) with reference lines. The use of a calibrator as an auxiliary gas-discharge cell for diode-laser absorption spectrometry of low-temperature plasma was demonstrated. When a high-frequency discharge was excited in the starter by an outer ring electrode, a signal of 30% absorption at the 1s5 → 2p9 transition of metastable Ar* atoms was recorded with a low noise level. This result is evidence of the possibility of using the calibrator as an optical reference for simple systems of laser-frequency stabilization or for investigating the shifts of spectroscopic lines of Ar or Ne atoms.

Temperature and pressure in a sealed Ar cell of an optical wavelength calibrator are measured using diode laser spectroscopy. The values of the thermodynamic parameters allowed determination of the fluctuations of the shift of the argon line at 811.5 nm. The expected fluctuation amplitude appears lower than ±15 MHz. The result obtained indicates the applicability of the studied calibrator as an optical reference and the correctness of previous measurements of pressure shift coefficients of the 811.5 nm argon line.

In this work simultaneous measurements of pressure broadening and shift coefficients for 811.5 nm Ar and 811.3 nm Kr spectral lines of the 4s[3/2](2) -> 4p[5/2](3) transition were performed. Assessment of gas temperature was done by determining Doppler width components of the lines' Voigt profiles. Pressure shift coefficients for the mixtures Ar:Ne, Kr:Ne and Kr:Ar were determined for the first time. Their values in units of 10(-1)0 s(-1) cm(3), reduced to 300 K are: beta(Ar:Ne)= -0.51 +/- 0.05, beta(Kr:Ne)= -0.65 +/- 0.01, beta(Kr:Ar) = -2.07 +/- 0.08. Additionally we demonstrated the use of easily available starters for fluorescent lamps as sealed Ar discharge cells for reference optical frequency. (C) 2018 Elsevier Ltd. All rights reserved.

Optically pumped all-rare-gas laser (OPRGL) with unique properties were recently proposed with a possibility to obtain the laser power on the order of hundreds of Watts from a cubic centimeter. To provide high laser efficiency, the pumping radiation has to match the absorption spectrum of the rare gas metastables. To meet this condition a reliable diagnostics of the key parameters of the active medium is required and knowledge of the broadening and shift coefficients for corresponding transitions of rare gases is necessary. In this paper, the diode-laser absorption spectroscopy was employed to determine the pressure shift coefficient for 811.5 nm Ar line. The value of obtained coefficient in pure argon reduced to 300 K is -(2.1 ± 0.1) × 10-10 s-1cm3. In the course of the study the pressure broadening coefficient was also evaluated and found to be (2.4 ± 0.5) × 10-10 s-1cm3.

Absorption spectroscopy measurements of long-lived metastable argon atoms Ar* in a low-pressure RF-discharge were carried out to measure gas leaks in a vacuum chamber. Argon as a carrier gas was flowing through the test chamber and the discharge cell at a rate of 55 mu mol/s. If a leak occurs, the ambient air is admixed to the carrier gas flowing through the test chamber. The presence of air in the carrier gas flowing through the discharge plasma produced a decrease in the number density of [Ar*], which was measured by means of diode laser absorption spectroscopy. This is because the lifetime of atoms is limited by losses due to collisions with air molecules. The leak-rate of the ambient air ranged from 0.14 to 0.95 mu mol/s was measured by a mass flow meter and compared with the amplitude of the absorption signal.