High-power thulium-doped fiber laser systems

Active fibers based on thulium-doped fused silica enable high-power laser amplification at around 2 µm wavelength. Doubling the operation wavelength, as compared to their ytterbium-based counterparts, makes thulium-doped fiber laser systems promising candidates for the generation of high-average-power ultrashort pulses with record-breaking peak power. This expectation is based on the beneficial wavelength dependencies of most unwanted nonlinear effects and the fact that increasing the operation wavelength allows to simultaneously increase the transverse fiber dimensions, while maintaining effective single-mode operation. In our group, we exploit these dependencies to push the performance limits of ultrafast fiber laser systems. Additionally, we harness the fundamental advantages of longer driving wavelengths in nonlinear frequency conversion and address highly application-relevant spectral regions such as the THz, the mid-infrared, and the soft X-ray.