Abstract
3 at.% Tm, x at.% Y:CaF2 crystals (x=0, 0.5, 1, 2, and 3) were grown by the vertical Bridgman method and investigated. Codoping Y3+ ions can manipulate the local structure of Tm3+ ions in the CaF2 crystal and then improve the spectroscopic properties. Compared with 3 at.% Tm:CaF2, 3 at.% Tm, 3 at.% Y:CaF2 crystal has several advantages. Firstly, the absorption cross section is improved from 0.35 × 10−20 cm−2 to 0.45 × 10−20 cm−2 at 767 nm, and the fluorescence intensity had elevated 3.4 times. Secondly, the linewidth of the fluorescence spectrum and lifetime also increased from 164 nm to 191 nm and from 6.16 ms to 8.15 ms at room temperature, respectively. Furthermore, quantum efficiency improved from 58.2% to 80.3%. The maximum laser output power of 583 mW and slope efficiency of 25.3% were achieved in 3 at.% Tm, 3 at.% Y:CaF2 crystal under 790 nm diode pumping.
Highlights
Calcium fluorides, as laser substrates, possess various advantages of large size, high thermal conductivity, well controlled crystal growth processes, and low nonlinear refractive coefficient
Nd,Y:CaF2 crystal, Y3+ ions were codoped in Nd:CaF2 crystal which substitute for Ca2+ forming complicated local structure that performs an effect on spectroscopic properties [8]
As the solid-state lasers medium, the doped Tm3+ calcium fluoride crystal proves the potential to achieve efficient compact diode-pumped lasers with an oscillation wavelength near 2 μm which could be directly pumped around 790 nm (3H6→3H4 absorption transition) due to much lower nonradiative losses caused by multiphonon relaxation [11]
Summary
As laser substrates, possess various advantages of large size, high thermal conductivity, well controlled crystal growth processes, and low nonlinear refractive coefficient. As the solid-state lasers medium, the doped Tm3+ calcium fluoride crystal proves the potential to achieve efficient compact diode-pumped lasers with an oscillation wavelength near 2 μm which could be directly pumped around 790 nm (3H6→3H4 absorption transition) due to much lower nonradiative losses caused by multiphonon relaxation [11]. Tm ions act both as a sensitizer and activator in a single-doped sample, meaning that a higher concentration is necessary for effective absorption of 800 nm laser excitation. We have carried out laser experiments and obtained continuous-wave laser output
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