Abstract:We investigate Kerr lens mode locking of Yb:Lu 2 O 3 thin-disk laser oscillators operating in the sub-100-fs regime. Pulses as short as 35 fs were generated at an average output power of 1.6 W. These are the shortest pulses directly emitted from a thin-disk laser oscillator. The optical spectrum of the 35-fs pulses is almost 3 times broader than the corresponding emission band of the gain crystal. At slightly longer pulse duration of 49 fs, we achieve an average power of 4.5 W. In addition, 10.7 W are obtained in 88-fs pulses, which is twice higher than the previous power record for ultrafast thin-disk lasers generating pulses shorter than 100 fs. Our results prove that Kerr lens mode-locked Yb:Lu 2 O 3 thin-disk lasers are a promising technology for further average power and pulse energy scaling of ultrafast high-power oscillators operating in the sub-100-fs regime. Pescher, W. Schweinberger, V. Pervak, E. Fill, O. Pronin, Z. Wei, F. Krausz, A. Apolonski, and J. Biegert, "High-power sub-two-cycle mid-infrared pulses at 100 MHz repetition rate," Nat. Photonics 9(11), 721-724 (2015). 8. F. Emaury, A. Diebold, C. J. Saraceno, and U. Keller, "Compact extreme ultraviolet source at megahertz pulse repetition rate with a low-noise ultrafast thin-disk laser oscillator," Optica 2(11), 980-984 (2015). 9. C. J. Saraceno, O. H. Heckl, C. R. E. Baer, C. Schriber, M. Golling, K. Beil, C. Kränkel, T. Südmeyer, G. Huber, and U. Keller, "Sub-100 femtosecond pulses from a SESAM modelocked thin disk laser," Appl. Phys. B 106(3), 559-562 (2012 Matuschek, and J. Aus der Au, "Semiconductor saturable absorber mirrors (SESAM's) for femtosecond to nanosecond pulse generation in solid-state lasers," IEEE

We report on, to the best of our knowledge, the first fs-laser-written waveguide laser in Yb3+:CaGdAlO4 (Yb:CALGO). With Yb:CALGO crystals grown in our labs, we obtained a slope efficiency of 69% and up to 2.4 W of continuous wave (cw) output power in a waveguide-laser configuration. Moreover, bulk laser experiments with Yb:CALGO were performed, and slope efficiencies up to 73%, optical-to-optical efficiencies of 65%, and maximum cw output powers of 3.3 W were reached. These are the highest efficiencies in the laser configuration with Yb:CALGO.

We present a high-peak-power SESAM-modelocked thin-disk laser (TDL) based on the gain material Yb-doped lutetia (Yb:LuO), which exceeds a peak-power of 10 MW for the first time. We generate pulses as short as 534 fs with an average power of 90 W and a peak power of 10.1 MW, and in addition a peak power as high as 12.3 MW with 616-fs pulses and 82-W average power. The center lasing wavelength is 1033 nm and the pulse repetition rates are around 10 MHz. We discuss and explain the current limitations with numerical models, which show that the current peak power is limited in soliton modelocking by the interplay of the gain bandwidth and the induced absorption in the SESAM with subsequent thermal lensing effects. We use our numerical model which is validated by the current experimental results to discuss a possible road map to scale the peak power into the 100-MW regime and at the same time reduce the pulse duration further to sub-200 fs. We consider Yb:LuO as currently the most promising gain material for the combination of high peak power and short pulse duration in the thin-disk-laser geometry.

Thin-disk laser experiments with Yb:CaGdAlO(4) (Yb:CALGO) have been performed. A slope efficiency of 70% and an optical-to-optical efficiency of 57% could be achieved with a maximum output power of 30.7 W. These are so far the highest efficiencies obtained with this material. Furthermore, tuning experiments were carried out leading to a tuning range of 90 nm in total and 50 nm with more than 20 W of output power. This is to the best of our knowledge the widest wavelength tuning range of any material demonstrated at this power level. For all experiments the thermal evolution of the crystal surface temperature during laser operation was investigated.

We propose a novel approach for strong alignment of gas-phase molecules for experiments at arbitrary repetition rates. A high-intracavity-power continuous-wave laser will provide the necessary ac electric field of 10(10)-10(11) W/cm(2). We demonstrate thin-disk lasers based on Yb:YAG and Yb:Lu(2)O(3) in a linear high-finesse resonator providing intracavity power levels in excess of 100 kW at pump power levels on the order of 50 W. The multi-longitudinal-mode operation of this laser avoids spatial-hole burning even in a linear standing-wave resonator. The system will be scaled up as in-vacuum system to allow for the generation of fields of 10(11) W/cm(2). This system will be directly applicable for experiments at modern X-ray light sources, such as synchrotrons or free-electron lasers, which operate at various very high repetition rates. This would allow to record molecular movies through temporally resolved diffractive imaging of fixed-in-space molecules, as well as the spectroscopic investigation of combined X-ray-NIR strong-field effects of atomic and molecular systems.