Lasing Characteristics of an Electron-Beam-Excited Thallium-Ion Laser
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Lasing Characteristics of an Electron-Beam-Excited Thallium-Ion Laser E. V. Belskayaa, P. A. Bokhana, P. P. Gugina, and Dm. E. Zakrevskya, * a
Rzhanov Institute of Semiconductor Physics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia *e-mail: [email protected] Received January 16, 2020; revised January 16, 2020; accepted January 28, 2020
Abstract—Lasing at Tl+ lines with λ = 1.922, 1.385, 0.595, 0.695, and 0.707 μm was obtained when pumping a Ne + Tl gas-vapor mixture by an electron beam and creating population inversion of Tl+ transitions in the charge exchange reaction; the lasing at the first two lines was implemented for the first time. A linear dependence of the lasing power on the pumping power was derived in the range of pumping parameters under study, which proves the efficiency of the electron-beam excitation. An average lasing power of 44 mW was attained at λ = 595 nm at a pulse repetition frequency of 1 kHz with an efficiency of ∼0.06%. Energy parameters of the laser were numerically simulated. Keywords: lasing, electron beam, thallium ion, charge exchange reaction, ion lasing lines, numerical simulation DOI: 10.1134/S1024856020040041
INTRODUCTION When gaseous media are excited by an electron beam (EB), most of the energy (~50–60%) is consumed in ionization; it is transferred to working particles (atoms and ions) mainly during two processes: recombination [1] and charge exchange [2]. Recombination processes are effective at high gas pressures and electron densities, for example, in excimer lasers, high-pressure heavy inert gas atom lasers, etc. Recombination processes can be accelerated via an increase in the ionization ratio, which is used, for example, in Ca+ and Sr+ lasers [2]. The charge-exchange reaction underlies the operation of both high- and low-pressure lasers due to its high rate constant (∼10−9–10−10 cm3 s−1). Low-pressure lasers are usually metal ion lasers. The main experimental results on the pumping of metal-vapor active media by low-energy EBs (up to 10 keV) were presented in [2–4]. The further development, production, and study of lasing upon excitation by low-energy electrons, especially in the UV and VUV spectral regions, slowed down, probably due to the difficulty or impossibility of ensuring electron beam parameters (energy, current, current density, medium pressure, and pumped volume) or their combination to provide optimal lasing conditions by common methods (hollow cathode discharge and grid discharges based on an abnormal discharge). Therefore, experiments on pumping active media by low-energy EBs generated by other methods (in particular, in open discharge) with a wider set of attainable parame-
ters (current density, current, and energy) are promising and can give new results. For example, lasing in a Pb atom (λ = 722.9 nm) was implemented and studied in [5]; no effects which limit the pulse repetition rate f upon gas discharge pumping where revealed under EB pumping. In [6], the EB pumping of a
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