High-power continuous-wave upconversion fiber laser at room temperature

Abstract

We report cw laser emission of a Pr, Yb-doped ${\mathrm{ZrF}}_4-{\mathrm{BaF}}_2-{\mathrm{LaF}}_3-{\mathrm{AlF}}_3-\mathrm{NaF}$ fiber in the red spectral region. Laser emission was achieved on the transition ${{}^{3}P}_0\to {{}^{3}F}_2 \left({\lambda }_L=635 \mathrm{nm}\right)$ with a Ti:sapphire pump laser tuned to ${\lambda }_p=850 \mathrm{nm}$. A maximum output power of $P_{\mathrm{out}}=675 \mathrm{mW}$ was obtained at an incident pump power of $P_{\mathrm{in}}=3.37 \mathrm{W}$. The output power was increased to $P_{\mathrm{out}}=1020 \mathrm{mW}$ when pumping with $P_{\mathrm{in}}=5.51 \mathrm{W}$ was provided by two Ti:sapphire lasers. A photon avalanche process was found to contribute strongly to the population of the upper laser level.