Sodium Vapor Active Element Excited by Nanosecond Optical Pulses
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TICAL SOURCES AND RECEIVERS FOR ENVIRONMENTAL STUDIES
Sodium Vapor Active Element Excited by Nanosecond Optical Pulses G. S. Evtushenkoa, b, T. D. Petukhova, V. B. Sukhanova, V. O. Troitskiia, A. N. Kuryaka, and M. V. Triguba, * a
V.E. Zuev Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences, Tomsk, 634055 Russia bScientific Research Institute—Federal Research Centre for Projects Evaluation and Consulting Services, Moscow, 123317 Russia *e-mail: [email protected] Received December 9, 2019; revised December 9, 2019; accepted January 22, 2020
Abstract—A transverse-pumped sodium vapor active element has been designed. A possibility of lasing at resonant transitions upon active medium excitation by nanosecond pulses of different energy and spectrum has been experimentally studied. The medium was pumped using a dye laser and a CuBr laser. The emission on sodium D lines was detected when pumping by yellow CuBr laser light. Keywords: lasers, radiation sources, optical pumping, spectroscopy, signal conversion DOI: 10.1134/S1024856020040053
INTRODUCTION Metal vapor lasers can be used for the solution of quite a few problems. The temperature in the upper atmosphere can be determined with the use of lidar technologies, which allow the study of spectral characteristics of alkali metal vapor emissions at altitudes above 100 km [1]; this implies the excitation of D1 and D2 levels. There are problems of adaptive optics system correction solved with the help of guide stars [2, 3]. High-speed visualization with active spectral filtering is one of prospective problems, where active metal vapor media can be used. The capabilities of visualization systems with brightness amplifiers at self-terminating transitions in metal vapors were shown in a number of works (for example, [4]). The development of active optics systems on the basis of alkali metal vapor media with high optical radiation conversion efficiency may be quite promising. The best results in terms of lasing power are obtained for cesium and rubidium vapor lasers, where the distance between D2 and D1 levels is 10 nm or more, and the D lines are in the near-IR region. High-power laser diodes are used for excitation of such lasers, which leads to the active development of this trend and the creation of high-power DPAL (Diode-Pumped Alkali Laser) systems [5–7]. Systems operating in the visible and near-IR spectral regions are the most common for the solution of problems of environmental monitoring and visual-optical diagnostics, where potassium and sodium vapor media are the most promising. The distance between D2 and D1 levels is 4 nm in the potassium atom and 0.6 nm in the sodium atom, which is significantly less than in cesium and rubidium. Due to the efficient exchange of
energy in the presence of a buffer gas at a sufficiently high pressure, a Boltzmann population distribution is set between the resonant levels of sodium. All this makes it difficult to create a high population inversion in a medium at sodium and potassium resonant transitions under
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