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Driving nonlinear processes in scientific and upcoming industrial applications has been a topic with increasing interest and activities in the last years. Examples are the production of very short wavelengths via direct driven plasma light-sources (incoherent) or high-harmonic generation (coherent), optical parametric chirped pulse amplification to different wavelengths and shorter pulses and direct pulse shortening via self-phase modulation and subsequent compression down to the few-cycle pulse duration regime. We report on multi100W ultrafast laser sources with 1ps pulse durations and below and

We investigate power-scaling of a Kerr lens mode-locked (KLM) Yb:Lu

High-power laser oscillators in the sub-100-fs pulse duration regime at megahertz repetition rates are compact and reliable alternatives to multi-stage amplifier systems. Sub-100-fs bulk oscillators based on Ti:sapphire — the working horses in ultrafast science — are currently limited to 3.5 W of average power [1]. In comparison, sub-100-fs bulk oscillators based on other gain materials have already reached 12.5 W [2]. However, thermal effects in the gain material are a severe challenge for further power-scaling [Fig. 1(a)].

We demonstrate a Kerr lens mode-locked thin-disk laser oscillator operating with 95-fs pulses at 21.1 W of average power. This is the highest average power achieved by any oscillator in the sub-100-fs regime.

We demonstrate broadband THz generation driven by an ultrafast thin-disk laser (TDL) oscillator. By optical rectification of 50-fs pulses at 61 MHz repetition rate in a collinear geometry in crystalline GaP, THz radiation with a central frequency at around 3.4 THz and a spectrum extending from below 1 THz to nearly 7 THz are generated. We realized a spectroscopic characterization of a GaP crystal and a benchmark measurement of the water-vapor absorption spectrum in the THz range. Sub-50-GHz resolution is achieved within a 5 THz bandwidth. Our experiments show the potential of ultrafast TDL oscillators for driving MHz-repetition-rate broadband THz systems.

We demonstrate the carrier-envelope offset (CEO) frequency stabilization of a Kerr lens mode-locked Yb:Lu

We present a proof-of-principle demonstration of THz generation driven by a short-pulse thin-disk laser (TDL) oscillator. The laser source is based on a directly diode-pumped Yb:Lu 2 O 3 gain crystal delivering 4 W average power in 50-fs pulses at 61 MHz repetition rate. Broadband THz radiation up to 6 THz is generated by optical rectification and detected via electrooptic sampling in GaP crystals. Our experiment shows the high potential of this power-scalable technology for driving MHz-repetition-rate broadband THz systems.

Ultrafast thin-disk lasers continue achieving higher average powers and pulse energies than other oscillator technologies. We discuss performance scaling and the ongoing race towards shorter pulse durations, which recently resulted in 30-fs from Yb-based thin-disk lasers.

We investigate Kerr lens mode locking of Yb:Lu

Ultrafast thin-disk laser (TDL) oscillators generated up to 275 W in pulses with several hundred femtosecond duration [1]. However, the combination of high average output power with short pulse duration is challenging: the power levels of ultrafast TDL oscillators operating in sub-100-fs pulses are currently limited to the sub-10 W regime. In the last years Kerr-Lens Modelocking (KLM) has been established as a successful alternative to SESAM-modelocking of TDLs. The KLM technique has shown to be advantageous for achieving shorter pulse durations at high power levels [2]. So far, nearly all KLM TDLs use Yb:YAG, which is the best developed gain material for the thin-disk configuration but limited in its emission bandwidth. For achieving shorter pulse durations, it is highly attractive to study KLM TDLs based on gain materials with broader emission bandwidth. Yb:LuO exhibits a more than twice broader emission bandwidth than Yb:YAG [3]. Using SESAM-modelocking, Yb:LuO TDLs achieved 141 W in 740-fs pulses [4] and 7 W in 142 fs [5]. Recently, the first Yb:LuO KLM TDL has been demonstrated, generating 165-fs pulses with an output power of 5.9 W [6]. However, the full emission bandwidth of Yb:LuO was so far never exploited in a TDL.

We evaluate limitations in pulse duration for Kerr-lens mode-locked Yb-based thin-disk lasers. The most critical factor is appropriate intracavity dispersion engineering, which enabled operation at 30-fs. Substantially shorter durations are within reach using new designs.

We demonstrate HHG inside a modelocked thin-disk laser. Diode-pumped at only 48 W, it drives HHG in xenon at 2.6×1013 W/cm2 and 300 W average power, generating XUV-light down to 60.7-nm at 17-MHz repetition rate.

We demonstrate the first Kerr lens mode-locked Yb:CaGdAlO4 (Yb:CALGO) thin-disk laser oscillator. It generates pulses with a duration of 30 fs at a central wavelength of 1048 nm and a repetition rate of 124 MHz. The laser emits the shortest pulses generated by a thin-disk laser oscillator, equal to the shortest pulse duration obtained by Yb-doped bulk oscillators. The average output power is currently limited to 150 mW by the low gain and limited disk quality. We expect that more suitable Yb:CALGO disks will enable substantially higher power levels with similar pulse durations.

We investigate Kerr lens mode locking of Yb:Lu2O3 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:Lu2O3 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.

THz-time-domain spectroscopy (THz-TDS) is a well-established tool for characterizing material properties and investigating dynamics of complex molecular systems. As the broadband THz generation typically relies on sub-100-fs laser pulses, most systems are currently driven by Ti:sapphire lasers. In the last years there has been a strong effort to replace Ti:sapphire systems with power-scalable Yb-based directly diode-pumped solid-state lasers (DPSSLs) [1]. Ultrafast DPSSLs generate higher average power with lower complexity and better efficiency. However, their potential for high-power broadband THz operation has not yet been fully exploited [2].

An Yb:LuO thin-disk laser generating 50-fs pulses at 4-W average output power and 50-MW intracavity peak power is CEO stabilized with 200-mrad integrated phase noise. Effects of repetition-rate stabilization onto the CEO noise are discussed.

Ultrafast thin-disk lasers (TDLs) are often thought to deliver longer pulses than bulk lasers (Fig. 1a). Here we prove that this assumption is wrong and demonstrate the shortest pulses from any Yb:Lu2O 3 and Yb:CaGdAlO 4 (Yb:CALGO) laser (cf. Tab. 1). Our Kerr lens mode-locked (KLM) Yb:Lu 2 O 3 TDL generates 4.5 W in 49-fs pulses and 1.7 W in 40-fs pulses (being 40 % shorter than Yb:Lu 2 O 3 bulk lasers [1]). In addition, we demonstrate the first KLM Yb:CALGO TDL. It generates 30-fs pulses, which is the shortest duration ever obtained from ultrafast TDLs [2,3] and equal to the shortest pulses obtained from Yb-bulk oscillators [4].