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LASER SYSTEMS AND MATERIALS
Lasing properties of chalcogenide glasses in the 5^6 ^m spectral range
B.I. Denker1, B.I. Galagan1, M.P. Frolov2, V.V. Koltashev2, V.G. Plotnichenko2, G.E. Snopatin3, M.V. Sukhanov3,
S.E. Sverchkov1, A.P. Velmuzhov3
ALT'22
1 - Prokkorov General Physics Institute of RAS, Vavilov str. 38, Moscow, Russia 2 - Lebedev Physical Institute of RAS, Leninsky prosp. 53, Moscow, Russia 3 - Prokkorov General Physics Institute of RAS, Dianov Fiber Optics Research Center,
Vavilov str. 38, Moscow, Russia 4 - Devyatykh Institute of Chemistry of High-Purity Substances of RAS, Tropinin str. 49, Nizhny Novgorod, Russia
glasser@lst.gpi.ru
The wavelengths range >4^m is just beginning to be filled with solid-state lasers. The list of potential low-pho-non-energy laser hosts siutable for this range includes chalcogenide (sulfide, selenide and telluride) glasses. The principal advantage of glasses over crystals is the possibility to draw optical fibers of them. Despite many efforts, no laser action in rare-earth doped chalcogenide glasses has been demonstrated in mid-infrared until recently. Now it is clear, that the reason was the insufficient purity of the glasses. S-H, Se-H and Ge-H groups (the main technological impurities in chalcogenide glasses) cause absorption losses at 4^6 ^m and quench the mid-infrared luminescence of rare earth ions. Only recently the progress in rare-earth doped chalcogenide glass technology has made it possible to fabricate high-purity glasses and optical fibers with optical losses as low as -0.5^1 dB/m in the mid-infrared.
At present investigation stage we have limited ourselves with selenide glasses and the trivalent rare earth ions (Ce3+, Pr3+, Tb3+) having luminescent transitions at 5^6 ^m, all of them ending at the ground level. Selenide glasses are transparent in approx. 1^15 ^m range and the mentioned rare earth transitions have high quantum yeild in them. The Ge-Ga-Se glass system was chosen for its high solubility of lanthanide ions.
Ce3+ ions have no absorption bands in the near infrared and have to be pumped resonantly into the metastable level at ~4 ^m. In contrast, Pr3+ and Tb3+ ions have a whole number of near-infrared absorption bands and can be pumped by several common laser sources. In our experiments [1-4] the highest output energy (34 mJ at -5.2 ^m) was obtained with Ce3+ doped bulk glass pumped by pulsed 4.1 ^m Fe2+:ZnSe laser (Fig.1). Wavelength tuning in the range of 4.5-5.6 ^m and passive Q-switching were also demonstrated. The highest CW output power (35 mW at ~5.2^m) was obtained with Tb3+ doped composite sulfo-selenide glass fiber pumped by ~2 ^m Tm3+ fiber laser (Fig. 2). The longest lasing wavelength (5.9 |im) was observed with bulk Pr3+doped glass.
35
^ 30
^ 25 LU
S; 20
50 100 150
Absorbed pump energy.
0,4 0.6
P. ,W
Fig.1. Ce3+ :glass laser output under pulsed Fe2+: ZnSe laser pumping at 4.1 ^m.
Fig.2. Tb3+ :glass fiber laser output under CW Tm3+: fiber laser pumping at 2 ^m.
Thus room-temperature 4.5-5.9 fim bulk and fiber glass lasers became reality. The investigations have been supported by RFBR grants 8-29-20079 mk, 20-02-00425 and by RSFgrant 22-22-00742.
[1] M.F.Churbanov et al, First demonstration of ~5^m laser action in terbium doped selenide glass, Appl. Phys. B, 126, 117-119(2020)
[2] M.F.Churbanov et al, Laser potential of Pr doped chalcogenide glass at 5-6 ^m spectral range, J. of Non-Cryst. Solids, 559, 120592(2021).
[3] P. Fjodorov et al, Mid-infrared laser performance of Ce-doped selenide glass. Optics express, 29, #17, 27674 (2021).
[4] B.I. Denker et al, Continuous Tb-doped fiber laser emitting at ~5.25 ^m, J. of Optics and Laser Technology, 154, 108355(2022).
