Next Generation Driver for Attosecond and Laser-plasma Physics

Abstract

The observation and manipulation of electron dynamics in matter call for attosecond light pulses, routinely available from high-order harmonic generation driven by few-femtosecond lasers. However, the energy limitation of these lasers supports only weak sources and correspondingly linear attosecond studies. Here we report on an optical parametric synthesizer designed for nonlinear attosecond optics and relativistic laser-plasma physics. This synthesizer uniquely combines ultra-relativistic focused intensities of about 10 20 W/cm 2 with a pulse duration of sub-two carrier-wave cycles. The coherent combination of two sequentially amplified and complementary spectral ranges yields sub-5-fs pulses with multi-TW peak power. The application of this source allows the generation of a broad spectral continuum at 100-eV photon energy in gases as well as high-order harmonics in relativistic plasmas. Unprecedented spatio-temporal confinement of light now permits the investigation of electric-fielddriven electron phenomena in the relativistic regime and ultimately the rise of next-generation intense isolated attosecond sources.The development and proliferation of intense lasers with sub-two optical-cycle duration during the past decade has allowed to create the tools and techniques for the observation and control of electronic motions in all forms of matter; a field nowadays known as attosecond physics 1 . These techniques have meanwhile provided direct time-domain access to a wide range of electron phenomena with a sub-fs resolution, such as miniscule delays in photo-emission timing 2,3 , charge migration in molecules 4, 5 and solids 6,7 , as well as collective electron motion in extreme laser-plasma interactions 8 . Powerful few-cycle laser pulses have traditionally been produced via chirped-pulse amplification (CPA) in titanium-doped sapphire (Ti:Sa) in conjunction with spectral broadening in gas-filled hollow-core fibres (HCF) 9 . CPA-based lasers have achieved peak powers beyond 1 PW, but only with pulse durations extending to about ten optical cycles or longer 10,11 . Spectral broadening in HCFs provides octave-spanning spectra, but the approach is still limited to pulses with a few millijoules in energy 12,13 . Due to these restrictions few-cycle-driven attosecond sources based on high-harmonic generation (HHG) in gas targets generally suffer from a low intensity, constituting a major limitation to pushing the frontiers of the field. Upscaling few-cycle-driven HHG to higher driving pulse energies [14][15][16] allows the generation of intense isolated attosecond pulses for time-resolved nonlinear optics experiments in the extreme-ultraviolet (XUV) spectral

Relativistic-intensity near-single-cycle light waveforms at kHz repetition rate

“…Recent developments have led to a significant increase in the power generated by few-cycle laser pulse sources. Broadband optical parametric chirped pulse amplifiers (OPCPAs) have succeeded in scaling up the peak power of few-cycle pulses to the multi-TW range [12][13][14] . However, due to their need for large pump energies of several hundreds of mJ, these systems usually operate only at low repetition rates (10 Hz), which denies proper CEP stabilization.…”

“…However, due to their need for large pump energies of several hundreds of mJ, these systems usually operate only at low repetition rates (10 Hz), which denies proper CEP stabilization. Nonetheless, because of their inherently high temporal contrast, OPCPA-based sources have recently enabled few-cycle-driven relativistic laser-plasma interactions at a 10-Hz repetition rate, demonstrating relativistic surface high-harmonic generation with sub-2cycle 13 and sub-3-cycle 10,14,15 pulses, as well as LWFA with 3-cycle pulses 16 .…”

Dispersion control for temporal contrast optimization

“…To measure the residual GD, the amplified pulses in the LWS-20 are adaptively compressed with the aid of a chirp-scan trace [31], which iteratively programs the Dazzler GD until the residual GD is fully compensated. Pulse compression to the sub-5-fs regime is additionally confirmed by the single-shot frequency-resolved optical gating (FROG) and single-shot second-harmonic autocorrelation (SHAC) techniques [1]. The measured residual GDs with the new stretcher are plotted in Fig.…”

“…In this paper, we demonstrate how to optimize the operating conditions of an AOPDF to preserve the temporal pulse contrast of the Light Wave Synthesizer 20 (LWS-20): a sub-twocycle, 16 TW peak power OPS system reported by Rivas et al [1]. First, we show that an AOPDF programmed with a non-monotonic group delay (GD) degrades the temporal contrast of output pulses on a picosecond time scale when its driving RF amplifier is saturated (Section 2).…”

Effect of plasma-core-induced self-guiding on phase matching of high-order harmonic generation in gases

“…Therefore, in the case of HHG experiments carried out using low-pressure gas cells, beam trapping and guiding require higher intensity. Still, the lasers used nowadays for HHG experiments can easily fulfill these higher-intensity requirements [20,21], and the intensity distribution in the interaction region can be determined by self-guiding.…”