All-fiber core-pumped polarization-maintaining Ho-doped laser at 2.05/2.09 μm with high efficiency

A scheme for a continuous-wave (CW) all-fiber polarization-maintaining (PM) holmium-doped laser at 2.05/2.09 μm with high efficiency core-pumped by a thulium-doped fiber (TDF) laser is proposed. In the simulation, a rate equation model for the Ho laser is established to provide a theoretical guidance for the experiment. In the experiment, the TDF pumping source for the holmium-doped fiber (HDF) laser has an output wavelength of 1.94 μm and an output power of 55 W. The HDF laser is designed as a linear cavity structure with center wavelengths of 2049.4 nm and 2088.6 nm, maximum output powers of 37.5 W and 36.3 W, and the corresponding slope efficiencies of 75.3% and 72.9%, respectively. In the all-fiber PM HDF laser system, a high-quality laser output with a polarization extinction ratio (PER) of 15.3 dB, power stability of 0.32%, and beam quality (M2) of 1.18 is achieved.