In supercontinuum generation, various propagation effects combine to produce a dramatic spectral broadening of intense ultrashort optical pulses. With a host of applications, supercontinuum sources are often required to possess a range of properties such as spectral coverage from the ultraviolet across the visible and into the infrared, shot-to-shot repeatability, high spectral energy density and an absence of complicated pulse splitting. Here we present an all-in-one solution, the first supercontinuum in a bulk homogeneous material extending from 450 nm into the mid-infrared. The spectrum spans 3.3 octaves and carries high spectral energy density (2 pJ nm−1–10 nJ nm−1), and the generation process has high shot-to-shot reproducibility and preserves the carrier-to-envelope phase. Our method, based on filamentation of femtosecond mid-infrared pulses in the anomalous dispersion regime, allows for compact new supercontinuum sources.
Strong-field ionisation surprises with richness beyond current understanding despite decade long investigations. Ionisation with mid-IR light has promptly revealed unexpected kinetic energy structures that seem related to unanticipated quantum trajectories of the electrons. We measure first 3D momentum distributions in the deep tunneling regime (γ = 0.3) and observe surprising new electron dynamics of near-zero momentum electrons and extremely low momentum structures, below the eV, despite very high quiver energies of 95 eV. Such level of high-precision measurements at only 1 meV above the threshold, despite 5 orders higher ponderomotive energies, has now become possible with a specifically developed ultrafast mid-IR light source in combination with a reaction microscope, thereby permitting a new level of investigations into mid-IR recollision physics.
The generation of few-cycle pulses with controlled waveforms in the mid-infrared spectral region is a longstanding challenge but is expected, to enable a new generation of high-field physics experiments, uncovering intricate physical phenomena. Successful generation of such optical pulses is limited by the tremendous spectral width -exceeding 1000 nm -required to withstand fewcycle pulses in the mid-IR correlated with the need to tightly control the spectral phase over such a broad bandwidth. Here, we present the first demonstration of sub-3 cycle optical pulses at 3.1 m central wavelength using for the first time self-compression in the anomalous dispersion regime in bulk material. The pulses emerging from this compact and efficient self-compression setup could be focused to intensities exceeding 10 14 W/cm 2 , a suitable range for high field physics experiments. Our experimental findings are corroborated by numerical simulations using a 3D nonlinear propagation code, therefore providing theoretical insight on the processes involved.Intense few-cycle pulses are difficult to obtain directly from a laser system due to limitations in amplification bandwidth, spectral reshaping and dispersion management. A solution to this problem is nonlinear propagation in gaseous media in capillaries [1] or free-space (filamentation) [2,3] and subsequent compression with chirped mirrors [4]. These techniques can reduce pulse durations from the typical 30 fs at 800 nm to below two-cycles, but, depending on implementation, efficiencies and pulse durations across the output beam may vary [5]. A lesser-known method to compress transform-limited pulses is based on group-velocity mismatch and fast amplitude modulation during three-wavemixing in a nonlinear crystal [6]. The technique was demonstrated for Nd:YAG wavelength and allowed compression from 10 ps duration to 310 fs while doubling the input frequency [7]. Self-compression to the few-cycle regime, i.e. without the need for dispersion compensation, was predicted [8] and achieved at 800 nm and 1500 nm wavelengths [9], but is limited in pulse energy due to rapid and chaotic pulse splitting [10,11].The current upsurge in activity to generate intense fewcycle pulses in the mid-IR motivates revisiting nonlinear propagation and pulse compression in those regimes. A limitation for applying the above-mentioned techniques is the typically insufficient pulse energy from mid-IR laser systems, which makes using gaseous media for nonlinear propagation challenging. The combination of low pulse energy and propagation in the anomalous dispersion regime is however suited to investigate self-compression in bulk media due to the much higher nonlinearities.In this Letter, we demonstrate stable and efficient selfcompression of mid-IR pulses in bulk material via filamentation in the anomalous dispersion regime. The spectro-temporal properties of the pulses resulting from this highly nonlinear interaction have been investigated and revealed durations as short as 3 optical cycles with energy throughpu...
An all-optical and passively carrier-to-envelope-phase-stabilized (CEP-stabilized) optical parametric chirped pulse amplification (OPCPA) system is demonstrated with sub-250-mrad CEP stability over 11 min and better than 100 mrad over 11 s. This is achieved without any electronic CEP stabilization loop for 160 kHz pulse repetition rate in the few cycle regime.
We investigated nonlinear photoemission from plasmonic films with femtosecond, mid-infrared pulses at 3.1 μm wavelength. Transition between regimes of multi-photon-induced and tunneling emission is demonstrated at an unprecedentedly low intensity of <1 GW/cm2. Thereby, strong-field nanophysics can be accessed at extremely low intensities by exploiting nanoscale plasmonic field confinement, enhancement and ponderomotive wavelength scaling at the same time. Results agree well with quantum mechanical modelling. Our scheme demonstrates an alternative paradigm and regime in strong-field physics.
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