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L’attitude d’Antoine d’Agata est en contraste total avec la posture attendue d’un photographe documentaire préoccupé par l’image-preuve. Ses images-outils font intervenir le personnage A, fiction chargée d’opérer un rapprochement avec les vérités que le photojournalisme ne peut pas – ou plus – supporter. Mais dans le développement de son œuvre polyphonique inspirée des situationnistes, les regards déployés par d’Agata s’aveuglent les uns les autres. D’autres vérités, temporaires, émergent alors, en dehors des signes et des pratiques balisés. Antoine d'Agata’s attitude contrasts sharply with the expected posture of documentary photographers concerned with the image as proof. His work with the image conceived as a tool involves a fictional character, A, whose task is to bring together the truths that photojournalism cannot – or can no longer – bear. Yet In the development of his polyphonic work inspired by the situationists, the different views presented by d'Agata avert each other’s gaze. A set of temporary truths emerges, remote from traditional signs and practices.

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 demonstrate broadband high-power terahertz (THz) generation at megahertz repetition rates by optical rectification in GaP driven by an ultrafast Yb-based thin-disk laser (TDL) oscillator. We investigate the influence of pulse duration in the range of 50–220 fs and thickness of the GaP crystal on the THz generation. Optimization of these parameters with respect to the broadest spectral bandwidth yields a gap-less THz spectrum extending to nearly 7 THz. We further tailor the driving laser and the THz generation parameters for the highest average power, demonstrating 0.3 mW THz radiation with a spectrum extending to 5 THz. This was achieved using a 0.5 mm thick GaP crystal pumped with a 95 fs, 20 W TDL, operating at 48 MHz repetition rate. We also provide a simple method to estimate the THz spectrum, which can be used for design and optimization of similar THz systems.

Ultrafast thin-disk laser (TDL) oscillators provide higher intracavity pulse energy, average power, and peak power levels than any other femtosecond laser oscillator technology. They are suitable for driving extreme nonlinear interactions directly inside the laser oscillator. High harmonic generation (HHG) driven inside ultrafast TDL oscillators is a very recent approach for the generation of coherent extreme ultraviolet (XUV) light at multi-megahertz repetition rates. In this paper, we review the current state of the development, discuss the technological potential, and give an outlook toward the future developments. We compare the current performance to established technologies and evaluate possible limitations. We discuss future improvements, such as reduction of the driving pulse duration and increase of the intracavity peak power, efficient extraction of the XUV light from the cavity, and carrier-envelope offset frequency stabilization of the generated XUV light. Due to the power scalability of the TDL concept and the possibility to operate in a spectrally broadened regime with pulse durations below the gain bandwidth limitation, intra-oscillator HHG with TDLs has a high potential for powerful table-top multi-megahertz coherent XUV light sources for science and applications.

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.

We demonstrate a compact XUV source based on intracavity high-harmonic generation driven inside a modelocked thin-disk laser oscillator, generating photons with energy up to 20.4 eV (17th harmonics) at a repetition rate of 17.35 MHz.

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 demonstrate a compact extreme ultraviolet (XUV) source based on high-harmonic generation (HHG) driven directly inside the cavity of a mode-locked thin-disk laser oscillator. The laser is directly diode-pumped at a power of only 51 W and operates at a wavelength of 1034 nm and a 17.35 MHz repetition rate. We drive HHG in a high-pressure xenon gas jet with an intracavity peak intensity of 2.8×1013 W/cm2 and 320 W of intracavity average power. Despite the high-pressure gas jet, the laser operates at high stability. We detect harmonics up to the 17th order (60.8 nm, 20.4 eV) and estimate a flux of 2.6×108 photons/s for the 11th harmonic (94 nm, 13.2 eV). Due to the power scalability of the thin-disk concept, this class of compact XUV sources has the potential to become a versatile tool for areas such as attosecond science, XUV spectroscopy, and high-resolution imaging.

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].