Self-compression to 24 MW peak power in a fused silica solid-core fiber using a high-repetition rate thulium-based fiber laser system

Abstract

Complementing ultrafast thulium-doped fiber-laser systems with a subsequent nonlinear pulse compression stage can enable unique laser parameters at around 2 µm operation wavelength. Significant pulse shortening and peak power enhancement have been accomplished using a fused silica solid-core fiber. In this fiber a pulse peak power of 24 MW was achieved without catastrophic damage due to self-focusing. As compared to operation in the well-explored 1 µm wavelength region, increasing the emission wavelength to 2 µm has a twofold advantage for nonlinear compression in fused-silica solid-core fibers. This is because, on the one hand the self-focusing limit scales quadratically with the wavelength. On the other hand the dispersion properties of fused silica allow for self-compression of ultrashort pulses beyond 1.3 µm wavelength, which leads to strong spectral broadening from very compact setups without the need for external compression. Using this technique we have generated 1.1 µJ-pulses with 24 fs FWHM pulse duration (<4 optical cycles), 24 MW peak power and 24.6 W of average power. To the best of our knowledge, this is the highest average power obtained from any nonlinear compression experiment around 2 µm wavelength and the first demonstration of peak powers beyond 20 MW within a fused-silica solid-core fiber. This result emphasizes that thulium-doped fiber-based chirped-pulse amplification systems may outperform their ytterbiumdoped counterparts in terms of peak power due to the fourfold increase of the critical power of self-focusing.