Pulse Energy Scaling of Thulium-Doped Fiber Lasers for Nonlinear Conversion into the Mid-Infrared

Thulium-doped fiber lasers deliver high-power 2 µm radiation but are constrained in pulsed operation by nonlinear effects and gain limitations. This work investigates pulse energy scaling through theoretical modeling and experiments, demonstrating a nanosecond-pulsed photonic crystal fiber laser that sets a new benchmark for 2 µm laser technology. Furthermore, the fiber laser enables highly efficient nonlinear conversion, paving the way for future >100 W mid-infrared sources.