Abstract:We present an ultrafast thin disk laser that generates an average output power of 275 W, which is higher than any other modelocked laser oscillator. It is based on the gain material Yb:YAG and operates at a pulse duration of 583 fs and a repetition rate of 16.3 MHz resulting in a pulse energy of 16.9 μJ and a peak power of 25.6 MW. A SESAM designed for high damage threshold initiated and stabilized soliton modelocking. We reduced the nonlinearity of the atmosphere inside the cavity by several orders of magnitude by operating the oscillator in a vacuum environment. Thus soliton modelocking was achieved at moderate amounts of self-phase modulation and negative group delay dispersion. Our approach opens a new avenue for power scaling femtosecond oscillators to the kW level. 435-453 (1996). 19201-19208 (2010). Huber, and U. Keller, "High-power ultrafast thin disk laser oscillators and their potential for sub-100-femtosecond pulse generation," Appl. Published in OpticsExpress 20, issue 21, 23535-23541, 2012 which should be used for any reference to this

We present a semiconductor saturable absorber mirror (SESAM) mode-locked thin-disk laser generating 80 μJ of pulse energy without additional amplification. This laser oscillator operates at a repetition rate of 3.03 MHz and delivers up to 242 W of average output power with a pulse duration of 1.07 ps, resulting in an output peak power of 66 MW. In order to minimize the parasitic nonlinearity of the air inside the laser cavity, the oscillator was operated in a vacuum environment. To start and stabilize soliton mode locking, we used an optimized high-damage threshold, low-loss SESAM. With this new milestone result, we have successfully scaled the pulse energy of ultrafast laser oscillators to a new performance regime and can predict that pulse energies of several hundreds of microjoules will become possible in the near future. Such lasers are interesting for both industrial and scientific applications, for example for precise micromachining and attosecond science.

We present a compact extreme ultraviolet (XUV) source based on high-harmonic generation (HHG) at 2.4 MHz pulse repetition rate driven from the compressed output of a mode-locked thin-disk laser (TDL) oscillator. The system generates very high peak intensities, which enable highly nonlinear frequency conversion reaching VUV/XUV energies. These sources significantly increase the signal-to-noise ratio and reduce measurement durations in many fields such as condensed matter physics. The pulse repetition rate is increased from kilohertz to megahertz with high average photon flux, while keeping the pulse energy sufficiently low to avoid space charge effects. The system uses a semiconductor saturable absorber mirror mode-locked Yb:YAG TDL delivering an average power of up to 70 W with subpicosecond pulses, which are efficiently compressed to sub-100 fs in a simple, single-stage compressor based on a Kagome-type hollow-core photonic crystal fiber. Focusing into a high-pressure xenon gas jet, we generate XUV radiation with up to >5 × 10 7 photons∕s on the 19th harmonic (23 eV). This HHG system is very compact, has low-noise performance comparable to standard ultrafast low-power laser oscillators, and provides a new tool for the study of attosecond dynamics in condensed matter physics.

SESAM modelocked thin-disk lasers have recently reached new frontiers and remain the leading technology in terms of average power and pulse energy, setting new performance levels for ultrafast oscillators. The milestones achieved seem to indicate that there are no major roadblocks ahead to achieve further scaling of modelocked oscillators to kilowatt output powers and millijoule output pulse energies. In this paper, we review the current state of the art and present the next steps toward future generations of millijoule, kilowatt-class ultrafast thin-disk oscillators.

We present a semiconductor saturable absorber mirror (SESAM) mode-locked thin disk laser (TDL) based on Yb:CaGdAlO 4 (Yb:CALGO) generating 62 fs pulses, which is the shortest pulse duration achieved from mode-locked TDLs to date. The oscillator operates at a repetition rate of 65 MHz and delivers 5.1 W of average output power. The short pulse duration of our TDL in combination with the high intracavity peak power of 44 MW makes this oscillator attractive for intracavity table-top extreme nonlinear optics applications such as high harmonic generation and vacuum ultraviolet frequency comb generation. The current average power was limited by the quality of the Yb:CALGO disk. However, power scaling of Yb:CALGO TDLs to the multi-10-W range with short pulse durations (<100 fs) appears feasible in the near future by using thinner disks of better quality and further optimized SESAMs.OCIS One interesting aspect of TDLs is the high intracavity peak power which can be realized because the output coupler typically has values in the order of 10%. This intracavity peak power should allow for extreme nonlinear frequency conversion such as high harmonic generation (HHG). Realizing those experiments at a high repetition rate in the MHz regime, typically obtained with ultrafast TDLs, is highly desirable for an improved signal-to-noise ratio and to reduce acquisition times in high field laser physics. However, for efficient operation, HHG typically requires peak intensities of >10 13 W∕cm 2 (i.e., peak powers of >30 MW for a spot diameter of 25 μm) in combination with short pulse durations <100 fs [8][9][10] [ Fig. 1(c)]. State of the art mode-locked TDLs are typically based on the well-established gain material Yb:YAG, which has only reached the 200-fs-regime so far with a Kerr lens mode-locked TDL setup [ 11].Therefore, there is a strong research effort in extending the record performance of mode-locked TDLs to the sub-100-fs regime [ Fig. 1(a)], and overcoming the tradeoff between pulse duration and average output power [ Fig. 1(b)] with novel broadband thin disk gain materials that meet the spectroscopic and thermomechanical requirements [12 , 13]. In the past years, many Yb-doped gain materials have been investigated toward this goal. In particular, cubic sesquioxides have demonstrated their