1.5-µm upconversion pumping of a continuous-wave Er³⁺:LiYF₄ waveguide laser operating at 2.8 µm

We report on the first, to the best of our knowledge, experimental characterization of an upconversion-pumped room-temperature continuous-wave (CW) operation of an Er³⁺:LiYF₄ channeled waveguide laser at 2810 nm. Pumping as well as the measurement of the upconversion excitation spectrum was achieved with a tunable CW Cr⁴⁺:YAG laser operating in the 1400-1525 nm range. The optimum upconversion pumping wavelength was determined to be 1513 nm and corresponded to the pump wavelength where the green upconversion of the Er³⁺:LiYF₄ medium was reduced. During CW operation at 2.8 µm, a maximum output power of 43 mW was obtained with 753 mW pump power at 1513 nm, corresponding to a power slope efficiency of 6.6%.