CC BY
14LS-P-12
Double-range RF Discharge Slab CO Laser
A.A. Ionin, A.Yu. Kozlov, A.A. Kotkov, Yu.M. Klimachev, O.A. Rulev, D.V. Sinitsyn
P.N.Lebedev Physical Institute of Russian Academy of Sciences, 53 Leninskiy prosp., 119991 Moscow, Russia
email: rulevoa@lebedev.ru
Carbon monoxide laser can operate on transitions of fundamental vibrational band in spectral range of A,~4.9-7.5 ^m [1] and on transitions of first vibrational overtone band of CO molecule (A,~2.5-4.2 ^m) [2]. The laser has high efficiency and its wide spectral range makes it possible to use this lasei for spectroscopy. The overtone CO laser emission overlaps the atmospheric transparency window. Moreover, this laser is a more suitable source of radiation for cutting glass and ceramics than a widely used CO2 laser [3]. In the Gas Lasers Lab of the Center for Laser and Nonlinear Optical Technologies, two RF discharge slab CO laser facilities with cryogenically cooled electrodes operating without forced replacement of the active gas mixture were previously developed [4-8]. But average lasei power of these lasers was not high enough for some applications, such as cutting glass, ceramics, or polymer materials. Higher laser power was required. Therefore, as extension of the previous experiments, we developed a new facility with an increased surface area and the length of its electrodes.
The laser chamber was designed as a cylinder with internal volume of ~28 l and was designed similar to the laser chamber described in [6]. The electrode system consisted of two hollow Au-coated copper electrodes of 470 mm length and 25 mm height. Discharge gap was 3-5 mm at different experiments. RF power supply with carrier frequency of 40 MHz and maximal output RF power up to 2 kW was operated in repetitively pulsed mode with low repetition rate of 100 Hz - 2 kHz.
To obtain lasing in free running mode on fundamental vibrational band of CO molecule, the hybrid positive branch unstable-waveguide 500 mm long internal cavity with Au-coated Cu mirrors with curvatures of 3600 and -2600 mm was used. The maximal averaged laser power of ~38 W was obtained under active medium pressure of 51 mbar, pulse repetition rate of 400 Hz, and pump pulse duration of 0.625 ms. A typical spectrum of the laser emission consisted of ~20 spectral lines in the wavelength range from 5.07 to 5.62 ^m
To carry out lasing on transitions of first overtone vibrational band of CO molecule in free-running mode, 500 mm long stable resonator formed by dichroic mirrors with high reflection in the spectral range corresponding to transitions of overtone band and low (<20%) reflection in the spectral range of 5.0-6.0 ^m was used. The maximal averaged laser power was ~5.7 W at active medium pressure of 25 mbar and the same pump conditions. Typical laser spectrum consisted of ~50 lines at the spectral range from 2.6 to 3.05 ^m.
To obtain lasing in Q-switching mode on transitions of CO molecule fundamental band, 2 m long stable double-pass V-type laser cavity with 50% reflection of output coupler was used. Q-switching was performed by a rotating mirror. Maximal peak power of laser radiation in these experiments was ~4.5 kW at pulse duration of ~1.3 ^s (FWHM) and RF pump pulse repetition rate of 145 Hz. The laser spectrum in this case consisted of ~100 spectral lines in the wavelength range of 4.95 - 7.0 ^m.
[1] A.A. Ionin "Electric Discharge CO Lasers" in [Gas Lasers], M. Endo and R.F. Walter eds, CRC Press - Taylor and Francis Group, Boca Raton, 201-237, 2007.
[2] A.A. Ionin, A.K. Kurnosov, A.P. Napartovich, L.V. Seleznev, "Lasers on Overtone Transitions of Carbon Monoxide Molecule"// Laser Physics, 20 (1), p.144, 2010.
[3] Ce Shi, M. Ermold, G. Oulundsen, and L. Newman "CO2 and CO laser comparison of glass and ceramic processing", Proc. SPIE 10911, p.109110M, 2019.
[4] A.A. Ionin, A.Yu. Kozlov, L.V. Seleznev, D.V. Sinitsyn, "RF discharge slab CO laser operating in both fundamental and first -overtone bands", Optics Communications, 282, p.629, 2009.
[5] A.A. Ionin, A.Yu. Kozlov, L.V. Seleznev, D.V. Sinitsyn, "Slab overtone CO laser operating in the 2.5 - 4.0 micron spectral range", IEEE Journal of Quantum Electronics, 45, (3), p.215, 2009.
[6] A.A. Ionin, A.Yu. Kozlov, O.A. Rulev, L.V. Seleznev, D.V. Sinitsyn, "Repetitively Pulsed Cryogenically Cooled Quasi Sealed-Off Slab RF Discharge First-Overtone CO Laser" Applied Physics B: Lasers and Optics, 122:183, 2016.
[7] A.A. Ionin, Yu.V. Kochetkov, A.Yu. Kozlov, et al., "Q-switched slab RF discharge CO laser", LaserPhys. Lett., 2017, 14, 055001.
[8] I.A. Chebotarev, A.A. Ionin, I.O. Kinyaevskiy, et al., "Frequency-selective Q-switched repetitively pulsed slab RF-discharge carbon monoxide laser", //Optics & Laser Technology, 131, 2020, 106431.
