The spectroscopic and laser properties of mixed fluoride Tm:CaF 2 -SrF 2 crystals were investigated. The 1.9 µm radiation was obtained in two samples with Tm 3+ ion doping concentrations of 1.0 mol% and 2.0 mol% under laser diode pumping at 763 nm. The highest slope efficiency of 32.5% and the widest laser tuning range of 232 nm (1761-1993 nm) were demonstrated with the 1%-doped sample. The maximal output power amplitude of 3.4 W at 1902 nm for an absorbed pump power amplitude of 13.8 W was demonstrated with the 2%doped sample.
The spectroscopic and laser characteristics of optically polished Cr:ZnSe single crystals in four different lengths of 2, 3, 5, and 10 mm were investigated when pumping with a laser diode generating radiation at the wavelength of ~1.69 μm. The optimization from the point of laser efficiency was done in dependence on the crystal samples active length, effect of antireflection (AR) coatings, pumping pulse duration, and repetition rate. As a result, a 3 mm thick anti-reflection coated Cr:ZnSe crystal pumped by a laser diode with a pulse length of 20 ms and repetition rate of 10 Hz was chosen as the optimal. Using a 0.8 mm thick MgF2 birefringent filter the laser oscillations were continuously tunable from 2.1 μm up to 2.7 μm with the narrow spectral linewidth of ~5 nm and Gaussian beam profile. Maximum mean output power of ~0.35 W and maximum optical-to-optical slope efficiency of ~39% was obtained for 3 mm thick AR-coated sample which was ~28% and ~10% higher than that for uncoated sample of the same thickness, respectively. Continuously tunable laser oscillation wavelength was measured in the range of ∼2.1-2.7 µm with the mean output power of P ≥ 150 mW within a ∼5 nm linewidth. The absorption and fluorescence spectra as well as fluorescence lifetime were also measured. The Cr2+ fluorescence lifetime of ∼7.2 µs measured for the 1 ns pulse excitation at room temperature (RT) was constant within the whole absorption band of 1.35–2.25 µm.
We present a temperature influence (in range from 78 up to 300 K) on the spectroscopic and laser properties of Tm:SrF2 crystal doped with 2 at. % of Tm3+. The sample was grown using the temperature gradient technique in shape of a single-crystal fiber (d= 2 mm, l = 5 mm) with plane-parallel face-polished without any AR coating. The Tm:SrF2 crystal was mounted in a temperature-controlled copper holder of the liquid nitrogen cryostat. The measured absorption and emission spectra remained broad even at low temperature. The fluorescence lifetime was fitted with a double exponential function, and the measured lifetime changed significantly with temperature decrease. The 147 mm long semi-hemispherical laser resonator consisted of a flat pumping mirror (T < 95 % @ 763 nm, HR @ 1750-2100 nm) placed inside the cryostat and a curved output coupler (r=150 mm, R=97.5 % @ 1750-2100 nm) placed outside the cryostat. For longitudinal pumping, a fiber coupled laser diode was used. The diode was operating in the pulse regime (5 ms pulse length, 10 Hz repetition rate) at wavelength 763 nm. At room temperature, the laser emission was achieved at 1949 nm with a high 38 % slope efficiency. With a temperature decrease, the slope efficiency increased, and the laser threshold decreased, and the laser output wavelength shifted.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.