Fei Wang, Haitao Huang^{*}, Haiwei Chen, Yushuo Bao, Zihan Li, and Deyuan Shen

Author Affiliations
School of Physics and Electronic Engineering, Jiangsu Normal University, Xuzhou 221116, Chinashow less

Abstract

The population trapping effect of the ${{}^{3}\mathrm{F}}_{4}$ level is an important factor limiting the power scaling of the 2.3 μm thulium (Tm) laser on the ${{}^{3}\mathrm{H}}_{4}\to {{}^{3}\mathrm{H}}_{5}$ transition. In this Letter, we demonstrate a novel scheme of ground state absorption (GSA) (${{}^{3}\mathrm{H}}_{6}\to {{}^{3}\mathrm{H}}_{4}$) and excited state absorption (ESA) (${{}^{3}\mathrm{F}}_{4}\to {{}^{3}\mathrm{H}}_{4}$) dual-wavelength pumped 2.3 μm Tm lasers. Introducing an ESA pumping process can accurately excite the ${\mathrm{Tm}}^{3+}$ ions accumulated in the ${{}^{3}\mathrm{F}}_{4}$ level to the ${{}^{3}\mathrm{H}}_{4}$ level, constructing a double populating mechanism for the upper laser level ${{}^{3}\mathrm{H}}_{4}$. A proof-of-principle experimental demonstration of the GSA (785 nm) and ESA (1470 nm) dual-wavelength pumped 2.3 μm $\mathrm{Tm}:{\mathrm{LiYF}}_{4}$ (Tm:YLF) laser was realized. A maximum continuous-wave output power of 1.84 W at 2308 nm was achieved under 785 and 1470 nm dual-wavelength pumping, increased by 60% compared with the case of 785 nm single-wavelength pumping under the same resonator condition. Our work provides an efficient way to achieve higher output power from 2.3 μm Tm-doped lasers on the ${{}^{3}\mathrm{H}}_{4}\to {{}^{3}\mathrm{H}}_{5}$ transition.