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In this work, the spectroscopy and laser characteristics of the ceramic Er:Y2O3 are presented in the temperature range from 80 to 300 K. Er:Y2O3 ceramic (5 at. % of Er3+, Baikowski Co., Ltd.) had the form of a rectangular block (thickness 9 mm) with plan-parallel polished faces (cross-section 3 × 3 mm) without anti-reflection coatings. The active medium was attached to the copper cold finger of the liquid nitrogen cryostat in a vacuum chamber. The pumping of Er:Y2O3 was carried out by radiation from fibre-coupled laser diode (pulse duration 3 ms, repetition rate 16.6 Hz, wavelength 972 nm). All spectroscopy measurements – transmission, fluorescence and up-conversion spectra together with fluorescence decay times at 4I11/2 and 4I13/2 were obtained in the temperature range from 80 to 300 K. The fluorescence decay time of manifold 4 I11/2 (upper laser level) is slightly increasing with rising temperature from 325 μs (80 K) to 342 μs (170 K) and then its decreasing to 295 μs (300 K). On the other hand, the decay time of lower laser lever 4I13/2 is increasing together with a rising temperature from 3.6 ms (80 K) to 4.6 ms (300 K). Moreover, it was obvious that with decreasing temperature, the intensity of green up-conversion radiation (564 nm) increased. For laser experiments a hemispherical resonator (80 mm in length) with a flat pumping mirror (HT < 94 % @ 960 - 980 nm and HR < 99 % @ 2.65 - 3 μm) and spherical output coupler (r = 100 mm, R = 95 % @ 2.65 - 2.95 μm) were used. Er:Y2O3 laser was operated in the pulsed regime to prevent damage to the active medium, the highest slope efficiency 9.5 % (with respect to absorbed power) and maximum output power of 83 mW were reached at a duty cycle of 5 %. With rising temperature the slope efficiency was decreasing down to 5 % at 300 K, on the other hand the laser threshold with respect to absorbed mean power was increased from 50 mW (80 K) to 150 mW (300 K). The emitted laser wavelength by the Er:Y2O3 laser was slightly changed due to the heating of the active medium from 2744 nm (at 80 K) to 2742 nm (at 300 K). The erbium-doped ceramic active media can be used as an alternative to crystals because of its easier fabrication compared to single-crystal sesquioxides, which require high melting point and special materials for crucible during growing process.
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