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We present an efficient, single-stage ultrabroadband, CEP-stable multipass Ti:Sa amplifier. The system generates sub-13 fs, 3.2mJ laser pulses at a repetition rate of 1kHz [1]. The excellent long-term CEP stability of sub-150 mrad rms noise (75 h measurement, single shot, every shot data acquisition) was achieved by the combination of the feed-forward CEP stabilization technique for the seed-oscillator [2] with the single-shot CEP measurement of the amplified laser pulses at 1 kHz and a fast feedback which corrects for the CEP drift in the amplifier via an RF phase shifter [3]. In order to achieve (spectrally) ultrabroadband laser pulses supporting a sub-13 fs pulse duration, custom Gaussian filters in combination with an acousto-optic programmable dispersive filter (AOPDF Dazzler, Fastlite) are used to suppress the gain-narrowing process in the amplifier. Due to the large spectral bandwidth of FWHM > 130 nm, it was possible to further broaden the spectrum (and, therefore, to reduce the pulse duration) via a moderate self-phase modulation (SPM) process in bulk material. After the grating compressor, a telescope with a curved focusing mirror and a concave defocusing lens was used to decrease the beam size of the laser pulses. Here the lens acts as the nonlinear SPM medium. The pulses are afterwards compressed using chirped mirrors.

International audience; We demonstrate a single-stage, multipass Ti:sapphire amplifier capable of delivering sub-13 fs, 3.2 mJ pulses at a 1 kHz repetition rate. Gaussian filters are used to suppress the gain-narrowing effect, thereby enabling the achievement of an ultrabroadband flat-top spectrum with a FWHM > 130 nm. The carrier-envelope phase (CEP) of the output pulses is actively stabilized via the feed-forward scheme (for the oscillator) and a fast 1 kHz f-to-2f interferometer, which corrects the amplifier-induced CEP drift. The single-shot 75 h CEP measurement yielded rms noise of

We present a compact scheme for generating sub-10-fs, CEP-stable pulses. The output of a CEP-stable ultrabroadband 3-mJ, 12-fs Ti:Sa amplifier is spectrally broadened in bulk and compressed, resulting in sub-10 fs pulses.

By compensating the gain-narrowing process, we achieved 6 mJ pulses with >130 nm full bandwidth at 1 kHz in a multipass amplifier. Out-of-loop CEP noise measurement of such a broadband configuration yielded

A compact system for the generation of few-cycle multi-mJ Carrier Envelope Phase (CEP) stabilized pulses is presented. At the output 1.9 mJ, 5.7 fs pulses were achieved after hollow fiber compression (HFC) of 5 mJ, 25 fs circularly-polarized pulses from a Ti:sapphire multipass chirped pulse amplifier (CPA). Polarization control of the generated pulses was done using all reflective phase retarders which can be nearly arbitrarily scaled for increasing energies. The CEP noise from the amplifier system is shown to be 190 mrad rms over a period of more than 7 hours. The full system, i.e., oscillator, amplifier, CEP stabilization, and HFC is compact enough to fit on a standard optical table.

We introduce and experimentally validate a pulse picking technique based on a travelling-wave-type acousto-optic modulator (AOM) having the AOM carrier frequency synchronized to the repetition rate of the original pulse train. As a consequence, the phase noise characteristic of the original pulse train is largely preserved, rendering this technique suitable for applications requiring carrier-envelope phase stabilization. In a proof-of-principle experiment, the 1030-nm spectral part of an 74-MHz, carrier-envelope phase stable Ti:sapphire oscillator is amplified and reduced in pulse repetition frequency by a factor of two, maintaining an unprecedentedly low carrier-envelope phase noise spectral density of below 68 mrad. Furthermore, a comparative analysis reveals that the pulse-picking-induced additional amplitude noise is minimized, when the AOM is operated under synchronicity. The proposed scheme is particularly suitable when the down-picked repetition rate is still in the multi-MHz-range, where Pockels cells cannot be applied due to piezoelectric ringing.

Waveform-stabilized laser pulses have revolutionized the exploration of the electronic structure and dynamics of matter by serving as the technological basis for frequency-comb and attosecond spectroscopy. Their primary sources, mode-locked titanium-doped sapphire lasers and erbium/ytterbium-doped fibre lasers, deliver pulses with several nanojoules energy, which is insufficient for many important applications. Here we present the waveform-stabilized light source that is scalable to microjoule energy levels at the full (megahertz) repetition rate of the laser oscillator. A diode-pumped Kerr-lens-mode-locked Yb:YAG thin-disk laser combined with extracavity pulse compression yields waveform-stabilized few-cycle pulses (7.7 fs, 2.2 cycles) with a pulse energy of 0.15 μJ and an average power of 6 W. The demonstrated concept is scalable to pulse energies of several microjoules and near-gigawatt peak powers. The generation of attosecond pulses at the full repetition rate of the oscillator comes into reach. The presented system could serve as a primary source for frequency combs in the mid infrared and vacuum UV with unprecedented high power levels., Frequency combs have revolutionized the study of electronic structures and dynamics of matter but currently used lasers systems are limited in terms of achievable pulse energies. Here, Pronin et al. demonstrate few cycle pulse emission from a thin-disk laser with 150 nJ pulse energy and 7.7 fs pulse duration.

We demonstrate an alternative approach facilitating the use of a travelling-wave type acousto-optic modulator to pick pulses from a high-repetition-rate carrier-envelope phase stable pulse train where Pockels cells cannot be applied due to piezoelectric ringing.

The implementation of multilayer optics for the compression and delivery of few-cycle femtosecond pulses will be discussed in the case of several cutting-edge applications.

We combine high-finesse optical resonators and spatial-spectral interferometry to a highly phase-sensitive investigation technique for nonlinear light-matter interactions. We experimentally validate an ab initio model for the nonlinear response of a resonator housing a gas target, permitting the global optimization of intracavity conversion processes like high-order harmonic generation. We predict the feasibility of driving intracavity high-order harmonic generation far beyond intensity limitations observed in state-of-the-art systems by exploiting the intracavity nonlinearity to compress the pulses in time.

The origin of a 1/f noise contribution in the long-term carrier-envelope phase (CEP) measurements of mode-locked lasers is discussed. Using two different collinear interferometers for the out-of-loop characterization of feed-forward stabilized Ti:sapphire oscillators, we suppress a possible technical origin of 1/f noise to the extent possible. Both measurements indicate a lower limit of CEP frequency noise of 1 mHz/√Hz. Investigating several possible origins of this noise floor, we find a good agreement with a quantum noise mechanism that is directly induced by intracavity-amplified spontaneous emission (ASE). These findings enable direct access to ASE noise in short-pulse oscillators, which is very hard to characterize via repetition rate fluctuations. Finally, we discuss the possible consequences for frequency-comb-based timekeeping and frequency metrology, as well as for attosecond science.

The demand for ever shorter light pulses presents a challenge to the detection and stabilization of the carrier-envelope phase (CEP) in amplifier systems. Here we present a combination of single-shot detection and a fast actuator that is capable of measuring and correcting the CEP in every single shot emitted by a millijoule-scale, multi-kHz femtosecond laser amplifier. The residual CEP noise within 50 s amounts to 98 mrad rms in-loop (fast detection, 5·105 shots) and 140 mrad out-of-loop (slow detection, 6250 shots), approaching the noise floor of the f-to-2f measurement. Both values represent a twofold improvement of the CEP stability over previously published results in comparable systems.

We demonstrate a simple and robust single-shot interferometric technique that allows the in situ measurement of intensity-dependent phase changes experienced by ultrashort laser pulses upon nonlinear propagation. The technique is applied to the characterization of carrier-envelope phase noise in hollow fiber compressors both in the pressure gradient and in the static cell configuration. Measurements performed simultaneously with conventional f-to-2f interferometers before and after compression indicate that the noise emerging in the waveguide adds up arithmetically to the phase noise of the amplifier, thus being strongly correlated to the phase noise of the pulses coupled into the compressor.

A method for improved performance of feed-forward carrier-envelope phase stabilization in amplified laser sources is presented and experimentally demonstrated. The phase stabilization scheme is applicable for a broad range of repetition rates spanning from subhertz to 100 kHz. The method relies on driving an acousto-optic frequency shifter by few-cycle transients. The phase of these transients suitably controls the grating phase of the generated index grating inside the shifter material. This approach removes beam pointing as well as amplitude noise issues observed in continuously driven feed-forward schemes. The synthesis of these gratings can be understood as the acoustic equivalent of mode-locking or acoustic frequency combs.

We demonstrate a novel scheme for improved feed-forward CEP stabilization of laser amplifiers. Synthesized acoustic few-cycle transients are used to stabilize the CEP of an optical pulse train at the amplifier repetition rate.

We report on a single-shot, in-situ interferometric method for measuring intensity-dependent phase changes in laser pulse propagation. With this method, the impact of hollow fiber compressors on phase stability was characterized.

We demonstrate a novel scheme for improved feed-forward carrier-envelope phase stabilization of amplified laser sources. Electrical few-cycle pulses are used to drive an acousto-optical frequency shifter to generate bursts of CEP stabilized seed pulses at the amplifier repetition rate.

The carrier-envelope phase of every single shot emitted by a 10 kHz, mJ-class amplifier is measured with a fast spectrometer. A novel high-speed actuator allows arbitrary phase control, with closed-loop integrated phase noise on seed oscillator level (98 mrad, 500000 shots, 50 s).

We present a single-shot, in-situ interferometric method for measuring phase changes experienced by laser pulses upon nonlinear propagation. With this method we characterized the intensity-dependent phase fluctuations emerging in hollow fiber compressors.

The thin-disk (TD) technology allowed reaching unprecedentedly high average powers and high energies with sub-ps pulses directly from oscillators. Such oscillators can be considered as an extremely attractive alternative to Ti:Sa oscillators, the working horses of the ultrafast community. However, two more features are missing to make TD oscillators a suitable substitute to Ti:Sa oscillators: few cycle pulses (

A femtosecond thin-disk Yb:YAG oscillator in both the anomalous and the normal dispersion regime is demonstrated. Both regimes are realized with practically the same resonator configuration. The power scaling potential of the anomalous and normal dispersion regimes is analyzed both theoretically and experimentally. The recipe to obtain Kerr-lens mode-locking (KLM) in the thin-disk configuration is presented here and oscillator characteristics as well as start-up difficulties are described. The oscillator stability in terms of output power, beam pointing and sensitivity to back reflections is measured and corresponds to the level of commercial systems.

After introducing some fundamental concepts and definitions for carrier-envelope stabilization schemes and frequency combs, measurement schemes for the carrier-envelope phase of oscillators and amplified systems are discussed. In particular, care is taken to point out typical problems in the experimental implementation of such schemes and to indicate ways to eliminate or reduce these issues. One of these potential problems is interferometer drift, another limiting factor may be shot noise in the photo detection. After this overview on detection of the carrier-envelope phase, techniques for its active stabilization are discussed. Two major approaches are addressed: the traditional feedback technique and the recently introduced feed-forward technique. Shortcomings and advantages of either technique are carefully compared and discussed. Finally, characterization methods are discussed, including example measurements that were recently obtained with the feed-forward method. These measurements indicate the smallest residual carrier-envelope phase jitter that was ever reported.

Carrier-envelope phase (CEP) stabilization of thin-disk oscillator with 200 mrad RMS noise measured in out-of-loop interferometer is demonstrated for the first time. The oscillator operates with 5.5% output coupler and delivers 17 W, 0.4 µJ pulses.

A power-scalable concept for carrier-envelope-phase stabilization is presented. It takes advantage of simultaneous pumping of the zero- and first-phonon absorption line of Yb:YAG at 969 and 940 nm. The concept was implemented to lock the carrier-envelope-offset frequency of a 45 W average power Kerr-lens mode-locked thin-disk oscillator. The lock performance is compared to previous experiments where carrier-envelope-stabilization was realized by means of cavity loss modulation.

The feed-forward technique has recently revolutionized carrier-envelope phase (CEP) stabilization, enabling unprecedented values of residual phase jitter. Nevertheless, its demonstrations have hitherto remained in a proof-of-principle state. Here we show that pulse quality and power issues can be solved, leading to few-cycle pulses with good beam quality. Making use of stable interferometers, we achieve day-long CEP-stable operation of the setup. Out-of-loop RMS phase noise amounts to less than 30 mrad in 20 s, with more than 24 h of CEP-locked operation being demonstrated.

The feed-forward technique has recently revolutionized carrier-envelope phase stabilization, enabling unprecedented values of residual phase jitter. Nevertheless, in its original demonstrations the stabilized beam exhibited angular and temporal dispersion. We demonstrate that these problems can be solved, resulting in few-cycle pulses with good beam quality. This in turn enables the use of monolithic interferometers, providing excellent long-term stability of the system. Out-of-loop RMS phase noise of less than 80 mrad over 33 minutes (0.5 mHz to 5 kHz) is measured, i.e., a value that has previously been reported for a few seconds integration time. The current method promises to enable reliable operation of CEP-stable systems over several days.

Feed-forward carrier-envelope phase (CEP) stabilization yields few-cycle pulses with unparalleled long-term precision. We show first results on the CEP control of pulses from a thin-disk laser, representing possible future attosecond driver sources.

The rapid progress in many areas of ultrafast science is steadily increasing the requirements on carrier-envelope phase (CEP) stabilization. While suitable sources for attosecond/high-field experiments remain limited to kHz repetition rates, two factors are of key importance to successful experiments: Tight CEP control and robustness over long timescales [1]. Utilizing a phase-locked loop, the conventional CEP locking scheme inevitably implies a trade-off between these two. On the other hand, applications for few-cycle pulses directly from the oscillator [2,3] greatly benefit from f CE = 0, which comes at an expense of performance and increased complexity.

A compact system for the generation of few-cycle multi-mJ carrier envelope phase (CEP) stabilized pulses is presented. The output 5.4 fs, 1.9 mJ pulses have CEP noise of only 190 mrad rms over seven hours.

The optimal enhancement of broadband optical pulses in a passive resonator requires a seeding pulse train with a specific carrier-envelope-offset frequency. Here, we control the phase of the cavity mirrors to tune the offset frequency for which a given comb is optimally enhanced. This enables the enhancement of a zero-offset-frequency train of sub-30-fs pulses to multi-kW average powers. The combination of pulse duration, power, and zero phase slip constitutes a crucial step toward the generation of attosecond pulses at multi-10-MHz repetition rates. In addition, this control affords the enhancement of pulses generated by difference-frequency mixing, e.g., for mid-infrared spectroscopy.