Modeling of a high-power continuous wave Yb:YAG planar waveguide amplifier under thermal steady-state

The performance of a novel, to the best of our knowledge, high-power Yb:YAG planar waveguide amplifier under thermal steady-state is studied numerically. We present a 3D thermal steady-state amplification model, which considers the effects of temperature on the Boltzmann occupation factors, pump absorption, and laser emission cross sections, in addition to reabsorption and pump saturation of Yb:YAG. The performance of a multipass-pumped planar waveguide amplifier under thermal steady-state was simulated considering the loss in the claddings, and a comparison with the simulated results under the ideal state was carried out. Our analysis results show that the core's temperature rise and the claddings' pump absorption lead to decreased pump absorption and optical-optical efficiencies. However, a high pump absorption efficiency (96%) and optical-optical efficiency (61.2%) are achieved when the pump power is 10 kW. Meanwhile, a lower fracture and minor thermal distortion can be expected in reality.