Thermal modeling of resonantly pumped high power Tm-doped fiber amplifiers

A thermal model concerning resonantly pumped high power Tm-doped fiber amplifiers is established with temperature dependent parameters taken into consideration. With this model, performance of resonantly pumped Tm-doped fiber amplifiers at 1 kW output is investigated. Comparisons with the traditional 793 nm LD pump scheme shows that, resonant pumping, especially the 1.9 μm pump, is more favorable for high power Tm-doped fiber systems, featuring high operation efficiency with low heat load, limited temperature rise, controllable beam compression and a relatively small laser intensity at the output end. Besides, the power scalability of resonantly pumped Tm-doped fiber systems with 25/250 double-clad fiber is also explored numerically with various thermal effects, optical damage and nonlinear effects taken in account. Simulations show that, for 1 GHz narrow linewidth output, outer cladding damage and stimulated Brillouin scattering are the two primary limiting factors for power scaling. And, the maximal output of a Tm-doped fiber amplifier could reach 5.1 kW and 6.8 kW for 1.6 μm pump and 1.9 μm pump, respectively. For systems with broad spectrum, output approaching 10 kW can be expected.