Cryogenic-cooled Tm:SBN tunable laser

摘要

In this work the temperature dependence of spectroscopic and laser properties of new active medium Tm:SBN (Strontium-Barium Niobate, SrxBa1_χNb206, x = 0.61) is presented. The tested sample Tm:SBN (2 wt. % of Tm2O3) is appropriate for generation of laser radiation at 1.88 fim. The Tm:SBN sample (thickness 6.65 mm) had plan-parallel polished faces without anti-reflection. During spectroscopy and laser experiments the Tm:SBN was attached to temperature-controlled copper holder and was placed in a vacuum chamber. The transmission and emission spectra of Tm:SBN and the fluorescence decay time were measured depending on temperature (80 - 350 K). The fluorescence decay time was measured to be 3.5 ms and 2.8 ms at 80 and 350 K, respectively. Longitudinal excitation of Tm:SBN was carried out by a fibre-coupled laser diode (pulse duration 10 ms, repetition rate 10 Hz, pump wavelength 793 nm). The laser resonator was hemispherical, 146 mm long, with flat pumping mirror (HR @1.8 - 2.1 μm) and spherical output coupler (r = 150 mm, R = 97.5 % @1.8 - 2.1 μm). The Tnv.SBN laser properties were investigated at temperature range 80 - 300 K. The highest slope efficiency with respect to absorbed pumped power was 3 % at 80 K. The maximum output peak amplitude power was 0.12 W at 80 K, i.e. 3.2 times higher than it was measured at 200 K. Tunability of laser wavelength at 80 K in the range of 1827 - 1962 nm was obtained by using SiO2 birefringent filter. At 300 K, wavelength tunability reached 1859 - 1970 nm. Thus, the new Tm:SBN crystal can be a promising laser material in the region of 2 μm.