We propose the generation of a widely tunable UV-to-IR frequency comb by high-order sideband generation (HSB) spectrum emitted from semiconductors. In our theoretical simulations, we demonstrate the high-order sideband signals of two series (2m Omega(seed) + (2n + 1)omega(driver), and (2m + 1)Omega(seed) + 2 n omega(driver)), where m and n are integers of a seed pulse and a driver laser frequency, respectively. The simulations also reveal the intensity of HSB scale with the driver laser power, both perturbatively and non-perturbatively. We find that the harmonic position and spacing of the high-order sideband emission can be controlled by varying the seed pulse and driver photon energies. In the experiment, we applied a visible ((h) over bar Omega(seed) = 3.1 eV, similar to 400 nm) seed pulse and mid-infrared (MIR, (h) over bar omega(driver) = 0.4 eV, 3.1 mu m) driver pulses to ZnSe target. Our experimental observations confirmed the UV (4.7 eV, 263 nm and 3.9 eV, 317 nm) HSB generation.

We propose Type-II SHG-autocorrelation as a simple and robust tool for high-dynamic range pulse-contrast measurements of sub-μJ energy, high-repetition rate pulses. We demonstrate dynamic ranges of the autocorrelation of over 10^7 with input energies of 55 nJ at 1 MHz repetition rate. The device allows temporal resolutions of 25 fs over a wide scanning range of 1100 ps, supporting input wavelengths from 700-1200 nm. The technique provides the perfect tool for wide use pulse-contrast measurement and optimization, possibly enabling a more effective use of pulse energy in peak power driven material processing applications.

We report an optical parametric amplifier (OPA), providing a maximum pulse energy of ∼200 µJ at 700-950 nm and a pulse duration of ∼1 ps. The OPA is driven by a ∼1 ps pulse with ∼2.5 mJ energy at 1 kHz, provided by a commercial thin-disk based laser. Using the output pulse of the OPA as pump, the thin-disk laser pulses at 1030 nm as Stokes, and the second harmonic (515 nm) as probe, we investigate the coherent anti-Stokes Raman scattering (CARS) of N2 and CO2 at various temperatures.

Coherent anti-Stokes Raman spectroscopy (CARS) is a powerful tool in combustion diagnostics [1] . It requires three beams, the pump, Stokes and probe beam with at least two different wavelengths. For high pressure applications, the use of fs-pulses is of additional benefit, as the CARS signal is free from distortions from molecular collisions, if the excited Raman level is probed within a few ps [2] . On the other hand, too short pulses (~100-500 fs) result in poor spectral resolution [3] . In this study, we present an optical parametric amplifier (OPA), providing a maximum pulse energy of ~200 µJ, at 700-900 nm and a pulse duration of ~1 ps. Using a pump source at 1030 nm, this setup may serve as a customized fs-CARS system for high pressure gas analysis.

We demonstrate a Type-II SHG-autocorrelator, enabling pulse contrast measurements for the nJ-energy range with signal-to-noise ratios of more than 10 7 . The setup features temporal resolution of 25 fs with a wide scanrange of 1100 ps.

We present a MgO:PPLN- and AgGaSe2-based, picosecond OPG/OPA scheme, enabling the generation of mid-to-long-infrared continuously tunable, microjoule energy pulses with a narrow spectral bandwidth of sub-8 cm-1 over the full tuning range. The approach combines a 1-µm-pumped, double-pass OPG setup with a 2-µm-pumped parametric booster amplifier stage. As pump laser is applied a CPA-free Ho:YLF laser delivering 32 µJ at 2051 nm wavelength and 20 kHz repetition rate. The OPG/OPA system specifications of µJ-level pulse energies in combination with narrowband and widely tunable, mid-to-long-IR spectra enable numerous possibilities for mid-IR spectroscopy and wavelength-specific mid-IR material processing.

We report on two different concepts to generate µJ-level mid-infrared laser pulses with sub-10 ps pulse duration via nonlinear parametric generation at high pulse repetition rates. Both schemes rely on the recent development of compact and efficient CPA-free, Ho:YLF-based 2-µm laser sources pumping the highly nonlinear crystal ZnGeP2 used for parametric amplification. The first concept comprises a simplified OPG/OPA scheme efficiently producing signal and idler radiation at fixed wavelengths of 3.0 and 6.5 µm, respectively. In the second concept, we demonstrate a wide spectral tunability of the picosecond, µJ pulses over the entire tuning range between 2.5 and 12 µm maintaining a constant bandwidth of sub-20 cm−1 by integrating a two-color pumping scheme and a spectral shaper into the setup. The presented compact and efficient mid-IR picosecond radiation sources offer a way towards low-cost mid-IR material processing and spectroscopic applications.

Summary form only given. The mid-to-long-infrared spectral range (3-15 μm) is of high interest for a multitude of material processing and spectroscopic applications due to wavelength-specific absorption features of many polymers and organic molecules in this spectral region. Especially narrowband, spectrally wide tunable mid-to-long-IR source reaching μJ-level pulse energies are attractive due to their ability to address specific absorption bands of the target materials. Common sources for narrowband, wide spectral tunable pulse generation are pico- or nanosecond optical parametric oscillators (OPO) or parametric amplifier systems (OPA) combined with a subsequent difference frequency generation stage in order to reach the mid-to-long-infrared spectral region [1]. In contrast optical parametric generators (OPG) possess a much higher simplicity of the optical design compared to OPOs or OPAs due the absence of specifically designed optical cavities nor the requirement of an optical seed. On the downside, the spectra generated in OPG systems are typically only limited by phase-matching constraints and therefore the generated bandwidth can be very broad and can vary significantly over the full spectral tuning range. Here we present an OPG/OPA scheme overcoming former OPG limitations by integrating a folded spectral shaper in a 1 gm pumped, double -pass OPG setup and combining it with a 2 gm pumped, ZnGeP2-based main parametric amplifier stage. As a result, the presented source enables the generation of narrowband, mid -to -long infrared continuously tunable, μJ -energy pulses with a stable spectral bandwidth of sub -20 cm -1 over the full tuning range from 2.5 to 12 μm wavelength at pulse repetition rates of 20 kH.

The laser-induced nonsequential double ionization (NSDI) of rare gas atoms in the near and mid-IR laser fields is studied experimentally and theoretically. We investigate electron-electron correlation at high recollision energies, experimentally achieving ponderomotive energies (U-p) above 80 eV. The contribution of the two dominant channels of NSDI in the photoelectron momentum distribution, impact, and excitation ionization, are both shown to scale with ponderomotive energy and are well reproduced by theory. Surprisingly, for a large U-p in mid-IR fields, a noticeable electron-electron anticorrelation signal emerges at low photoelectron momenta, which cannot be explained by these mechanisms within state-of-the-art theoretical approaches.

We demonstrate efficient generation of 1.35-optical-cycle (14.5 fs) and 60 µJ mid-IR pulses at 160 kHz repetition rate. The CEP-stable, 21 W mid-IR waveforms are self-compressed inside a gas-filled antiresonant-reflection photonic crystal fiber (ARR-PCF).

The speed of solid-state electronic devices, determined by the temporal dynamics of charge carriers, could potentially reach unprecedented petahertz frequencies through direct manipulation by optical fields, consisting in a million-fold increase from state-of-the-art technology. In graphene, charge carrier manipulation is facilitated by exceptionally strong coupling to optical fields, from which stems an important back-action of photoexcited carriers. Here we investigate the instantaneous response of graphene to ultrafast optical fields, elucidating the role of hot carriers on sub-100 fs timescales. The measured nonlinear response and its dependence on interaction time and field polarization reveal the back-action of hot carriers over timescales commensurate with the optical field. An intuitive picture is given for the carrier trajectories in response to the optical-field polarization state. We note that the peculiar interplay between optical fields and charge carriers in graphene may also apply to surface states in topological insulators with similar Dirac cone dispersion relations.

We demonstrate the first ZnGeP2-based, femtosecond OPA system driven directly by a Thulium-based fiber-laser system operated at 100 kHz. The OPA delivers mid-to-long-infrared tunable pulses with idler energies up to 2.2 pJ (23% quantum efficiency).

In attosecond and strong-field physics, the acquisition of data in an acceptable time demands the combination of high peak power with high average power. We report a 21 W mid-IR optical parametric chirped pulse amplifier (OPCPA) that generates 131 mu J and 97 fs (sub-9-cycle) pulses at a 160 kHz repetition rate and at a center wavelength of 3.25 mu m. Pulse-to-pulse stability of the carrier envelope phase (CEP)-stable output is excellent with a 0.33% rms over 288 million pulses (30 min) and compression close to a single optical cycle was achieved through soliton self-compression inside a gas-filled mid-IR antiresonant-guiding photonic crystal fiber. Without any additional compression device, stable generation of 14.5 fs (1.35-optical-cycle) pulses was achieved at an average power of 9.6 W. The resulting peak power of 3.9 GW in combination with the near-single-cycle duration and intrinsic CEP stability makes our OPCPA a key-enabling technology for the next generation of extreme photonics, strong-field attosecond research, and coherent x-ray science. (C) 2017 Optical Society of America

We report a 21-W mid-IR OPCPA that generates 131-{\mu}J and 97 fs (sub-9-cycle) pulses at 160 kHz repetition rate and at a centre wavelength of 3.25 {\mu}m. Pulse-to-pulse stability of the CEP-stable output is excellent with 0.33% rms over 288 million pulses (30 min) and compression close to a single optical cycle was achieved through soliton self- compression inside a gas-filled mid-IR anti-resonant-guiding photonic crystal fibre. Without any additional compression device, stable generation of 14.5 fs (1.35-optical-cycle) pulses was achieved at an average power of 9.6 W. The resulting peak power of 3.9 GW in combination with the near-single-cycle duration and intrinsic CEP stability, make our OPCPA a key-enabling technology for the next generation of extreme photonics, strong-field attosecond research and coherent X-ray science.

The temporal dynamics of charge carriers determines the speed with which electronics can be realized in condensed matter, and their direct manipulation with optical fields promises electronic processing at unprecedented petahertz frequencies, consisting in a million-fold increase from state of the art technology. Graphene is of particular interest for the implementation of petahertz optoelectronics due to its unique transport properties, such as high carrier mobility with near-ballistic transport and exceptionally strong coupling to optical fields. The back action of carriers in response to an optical field is therefore of key importance towards applications. Here we investigate the instantaneous response of graphene to petahertz optical fields and elucidate the role of hot carriers on a sub-100 fs timescale. Measurements of the nonlinear response and its dependence on interaction time and field polarization allow us to identify the back action of hot carriers over timescales that are commensurate with the optical field. An intuitive picture is given for the carrier trajectories in response to the optical-field polarization state. We note that the peculiar interplay between optical fields and charge carriers in graphene may also apply to surface states in topological insulators with similar Dirac cone dispersion relations.

Understanding strong-field double ionization of many-electron systems is an important fundamental problem with potential implications for molecular imaging within this regime. Using mid-IR radiation, we unambiguously identify the transition from nonsequential ($e, 2e$) to sequential double ionization in Xe at an intensity below ${10}^{14}\phantom{\rule{0.16em}{0ex}}\mathrm{W}/\mathrm{c}{\mathrm{m}}^{2}$. Ionization from excited orbitals is found to be decisive at low intensities, but we demonstrate that such mechanisms are unimportant in the sequential regime. We utilize these facts to successfully image a molecular dication using laser-induced electron diffraction. This methodology can be used to study molecular dynamics on unprecedented few-femtosecond time scales.

We present the first realization of a femtosecond, mid-to-long-infrared tunable OPA driven by a CPA Tm:fiber-laser with 100 kHz repetition rate. The source provides up to 0.75 μJ energy and supports sub-160 fs pulse durations.

Visualizing chemical reactions as they occur requires atomic spatial and femtosecond temporal resolution. Here, we report imaging of the molecular structure of acetylene (C2H2) 9 femtoseconds after ionization. Using mid-infrared laser-induced electron diffraction (LIED), we obtained snapshots as a proton departs the [C2H2](2+) ion. By introducing an additional laser field, we also demonstrate control over the ultrafast dissociation process and resolve different bond dynamics for molecules oriented parallel versus perpendicular to the LIED field. These measurements are in excellent agreement with a quantum chemical description of field-dressed molecular dynamics.

Many experimental investigations demand synchronized pulses at various wavelengths, ideally with very short pulse duration and high repetition rate. Here we describe a femtosecond multi-color optical parametric chirped pulse amplifier (OPCPA) with simultaneous outputs from the deep-UV to the mid-IR with optical synchronization. The high repetition rate of 160 kHz is well suited to compensate for low interaction probability or low cross section in strong-field interactions. Our source features high peak powers in the tens to hundreds of MW regime with pulse durations below 110 fs, which is ideal for pump-probe experiments of nonlinear and strong-field physics. We demonstrate its utility by strong-field ionization experiments of xenon in the near- to mid-IR.