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7*
ALT'23
The 30th International Conference on Advanced Laser Technologies
LS-I-2
Current progress in the investigation of rare earth doped
chalcogenide glass lasers
S. Sverchkov1, B. Denker1, M. Frolov2, B. Galagan1, V. Koltashev3, V. Plotnichenko3, G. Snopatin4, M. Sukhanov4, A. Velmuzhov4
'Prokhorov General Physics Institute of RAS, Vavilov str.38, Moscow, Russia 2P. N. Lebedev Physical Institute of RAS, Leninskiy Prosp. 53, Moscow, Russia 3Prokhorov General Physics Institute of RAS, Dianov Fiber Optics Research Center, Vavilov str.38, Moscow, Russia 4Devyatykh Institute of Chemistry of High-Purity Substances ofRAS, Tropinin str. 49, Nizhny Novgorod, Russia
In recent years, we have shown that rare earth doped chalcogenide glasses can serve as active materials for bulk and fiber mid-infrared lasers. Laser action in the spectral range from ~ 4.5 to ~ 5.5 ^m was demonstrated at the transitions between the first excited and the ground states of Ce3+, Pr3+ and Tb3+ ions [1, 2]. It was also shown, that in high purity selenide glasses even ~6 ^m rare-earth ion transitions can have high luminescence quantum yield. Over the past year, we have been working both on improving the existing chalcogenide glass lasers and on the new rare earth laser transitions.
In particular, the CW Tb3+ fiber laser output has reached 150 mW and the gain in Tb-doped fibers has reached 40-50 dB/m. It was found that up-conversion process (7F5+7F5^7F3+7F6) in heavily Tb-doped glasses may lead to the changeover from CW to non-relaxing spiky operation. Spiking can be suppressed by reducing the concentration of the active ion and/or by introduction of negative feedback into the laser cavity.
Ce3+ ions were made to generate CW laser radiation in chalcogenide fiber under pumping by a CW Fe2+:ZnSe laser. In contrast to Tb3+-doped mid-infrared fiber lasers, Ce3+-doped laser had no tendency to spike operation because the simple energy level structure of Ce3+ ions exclude up-conversion processes.
A novel sensitization scheme was proposed to excite 5-6 ^m Nd3+ emission in selenide glasses with the help of Tb3+ ions. It was shown, that at room temperature the radiationless energy transfer from Tb3+ to Nd3+ is combined with the reverse process. At liquid nitrogen temperature the energy transfer from Tb3+ to Nd3+ becomes irreversible.
Laser action of Nd3+ ions corresponding to 4In/2^%/2 transition was demonstrated for the first time. Up
to 16 mJ output was obtained. The left Figure shows the oscillograms of the pump 2.93 ^m Er:YAG laser pulse exciting Tb3+ ions (black) and Nd3+ ions lasing (red). Note the ~ 150 ^s time delay between the pump and the lasing pulses due to the finite Tb^Nd energy transfer rate. The right Figure shows the tuning range of Nd3+ laser reaching 6 ^m. It is the longest-wavelength glass laser for today.
[1] M.F. Churbanov et al., First demonstration of ~ 5 ^m laser action in terbium-doped selenide glass, Applied Physics B, 126, 116(2020).
[2] M.F. Churbanov et al., Comparison of 4.5-6 ^m luminescent and lasing properties of rare earth dopants in chalcogenide glasses, Journal of Luminescence, 245, 118756(2022).
