JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS, cilt.38, sa.8, 2021 (SCI-Expanded)
We experimentally demonstrate, for the first time to our knowledge, that upconversion pumping can be employed with a 1064-nm fiber laser to achieve tunable laser operation with 8 at. % Tm3+:KY3F10 crystal near 1.9 mu m, in addition to the previously explored upconversion pumping of the 2.3-mu m laser transition. Two different sets of cavity optics were used to investigate lasing at 1.9 and 2.3 mu m, corresponding to the laser transitions F-3(4)-H-3(6) and H-3(4)-H-3(5), respectively. In the case of the F-3(4)-H-3(6) laser transition, an x-cavity laser oscillator was constructed with a 2.3% output coupler and as high as 142 mW of output power was obtained at an incident pump power of 1.9 W at 1064 nm. Tunable laser operation could be obtained between 1849 and 1994 nm by using CaF2 and suprasil prisms. The highest slope efficiency of 29% with respect to average absorbed pump power was obtained with a 5.5% output coupler. For the case of 1.9 mu m lasing, it was further demonstrated that the nonlinear absorption of the crystal at 1064 nm depends on the intracavity laser intensity as well as the pump intensity. The H-3(4)-H-3(5) laser transition was also investigated with the same crystal in a z-cavity configuration under upconversion pumping, giving as high as 130 mW of output power at the central wavelength of 2344 nm with 1.6 W of incident pump power. (C) 2021 Optical Society of America