Tunable lasers based on diode pumped Tm-doped vanadates Tm:YVO4, Tm:GdVO4, and Tm:LuVO4

Thulium doped vanadates Tm:YVO4 (5 at.% Tm/Y, grown by the Czochralski technique), Tm:GdVO4 (2 and 6 at.% Tm/Gd, grown by the floating-zone technique), and Tm:LuVO4 (3 at.% Tm/Y, grown by the floating-zone technique) were investigated as an active medium for diode pumped tunable laser operating around 1.9 μm. For thulium laser tuning single 1.5mm thick Brewster-angled birefringent quartz plate (Lyot filter) was placed in simple 80mm long linear quasi-hemispherical resonator. For thulium doped vanadates pumping a fibre-coupled (core diameter 400 μm) temperature-tuned laser diode operating in range from 799 up to 810nm was used (max available power 20 W). All tested crystals were investigated under CW and pulsed pumping. Under pulsed pumping (4% duty-cycle, reduced heat generation) lasing and laser tuning was demonstrated with all available samples. Lasers were tunable in following wavelength ranges: Tm:YVO4 5 at.% Tm/Y (1841 - 1927 nm), Tm:GdVO4 2 at.% Tm/Gd (1830 - 1982 nm), 6 at.% Tm/Gd (1850 - 2010 nm), and Tm:LuVO4 3 at.% Tm/Lu (1860 - 1940 nm). Under CW pumping only Tm:GdVO4 crystal was lasing (lasing of Tm:YVO4 and Tm:LuVO4 was not reached under elevated pumping duty factor). Using Tm:GdVO4 (2 at.% Tm/Gd) the power up to 2.6W and slope effciency ~ 30% (with respect to absorbed power at 808nm under lasing condition) was obtained at wavelength 1.91 μm. Tunable operation with greater that 1W output and 130nm tuning range (1842 - 1972 nm) was demonstrated for Tm:GdVO4 (2 at.% Tm/Gd) pumped at 802 nm.

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