X-ray free-electron lasers (FELs) are state-of-the-art scientific tools capable to study matter on the scale of atomic processes. Since the initial operation of X-ray FELs more than a decade ago, several facilities with upgraded performance have been put in operation. Here we present the first lasing results of Athos, the soft X-ray FEL beamline of SwissFEL at the Paul Scherrer Institute in Switzerland.
View Article and Find Full Text PDFNon-linear materials are cornerstones of modern optics and electronics. Strong dependence on the intrinsic properties of particular materials, however, inhibits the at-will extension of demanding non-linear effects, especially those second-order ones, to widely adopted centrosymmetric materials (for example, silicon) and technologically important burgeoning spectral domains (for example, terahertz frequencies). Here we introduce a universal route to efficient non-linear responses enabled by exciting non-linear Thomson scattering, a fundamental process in electrodynamics that was known to occur only in relativistic electrons in metamaterial composed of linear materials.
View Article and Find Full Text PDFThe arrival time jitter and drift of the photocathode drive laser has an important impact on the performance of a Free-Electron-Laser (FEL). It adversely affects the beam energy jitter, bunch length jitter and bunch arrival time jitter, which becomes especially important for pump-probe experiments with femtosecond time resolution. To measure both parameters background free and stabilize the drift of the Yb:CaF based laser we use a well designed balanced optical cross correlator.
View Article and Find Full Text PDFA laser supercontinuum is generated by cross-phase modulation (XPM) driven by an intense terahertz (THz) field in organic crystal OHQ-N2S. In this highly nonlinear medium, the THz electric field induces a time-varying optical phase modulation, which causes a spectacular spectral broadening and shifting of a co-propagating near-infrared laser pulse. The effect is enabled by the large electro-optic coefficient, the low absorption, and the good velocity matching between the laser and the THz pulse over the OHQ-N2S crystal thickness.
View Article and Find Full Text PDFThe SwissFEL soft X-ray free-electron laser (FEL) beamline Athos will be ready for user operation in 2021. Its design includes a novel layout of alternating magnetic chicanes and short undulator segments. Together with the APPLE X architecture of undulators, the Athos branch can be operated in different modes producing FEL beams with unique characteristics ranging from attosecond pulse length to high-power modes.
View Article and Find Full Text PDFWe present proof-of-principle results on terahertz wavefront shaping by means of a deformable mirror (DM). The DM is based on a reflective gold-coated steel membrane pushed by 35 powerful stepper actuators to enable a surface deformation of up to 1 mm out of equilibrium. The maximum excursion is equivalent to 10 wavelengths of the terahertz source centered at 3 THz and, thus, offers excellent opportunities for shaping the terahertz wavefront and beam intensity profile.
View Article and Find Full Text PDFCharge-coupled devices (CCDs) are a well-established imaging technology in the visible and x-ray frequency ranges. However, the small quantum photon energies of terahertz radiation have hindered the use of this mature semiconductor technological platform in this frequency range, leaving terahertz imaging totally dependent on low-resolution bolometer technologies. Recently, it has been shown that silicon CCDs can detect terahertz photons at a high field, but the detection sensitivity is limited.
View Article and Find Full Text PDFWe report on the experimental observation of extreme laser spectral broadening and a change in optical transmission in gallium phosphite induced by 25 MV/cm terahertz (THz) single-cycle internal field. Such intense THz radiation leads to twofold transient modifications of the optical properties in the electro-optical crystal. First, the electric field provokes extensive cross-phase modulation via the χ^{(2)} and χ^{(3)} nonlinearities on a copropagating 50 fs near infrared laser pulse which turns into 500% spectral broadening.
View Article and Find Full Text PDFWe report on the generation of broadband, high-energy femtosecond pulses centered at 1.28 μm by stimulated Raman scattering in a pressurized hydrogen cell. Stimulated Raman scattering is performed by two chirped and delayed pulses originating from a multi-mJ Ti:sapphire amplifier.
View Article and Find Full Text PDFWe report on high-energy terahertz pulses by optical rectification (OR) in the organic crystal N-benzyl-2-methyl-4-nitroaniline (BNA) directly pumped by a conventional Ti:sapphire amplifier. The simple scheme provides an optical-to-terahertz conversion efficiency of 0.25% when pumped by collimated laser pulses with a duration of 50 fs and a central wavelength of 800 nm.
View Article and Find Full Text PDFPhotoinduced electron transitions can lead to significant changes of the macroscopic electronic properties in semiconductors. This principle is responsible for the detection of light with charge-coupled devices. Their spectral sensitivity is limited by the semiconductor bandgap which has restricted their visualization capabilities to the optical, ultraviolet, and X-ray regimes.
View Article and Find Full Text PDFHigh-field terahertz (THz) single-cycle pulses with 1.5 MV/cm are generated by optical rectification in the stilbazolium salt crystal 4-N,N-dimethylamino-4'-N'-methyl-stilbazolium 2,4,6-trimethylbenzenesulfonate. We show experimentally that the generated THz transient carrying 5 octaves (0.
View Article and Find Full Text PDFWe present the generation of high-power single-cycle terahertz (THz) pulses in the organic salt crystal 2-[3-(4-hydroxystyryl)-5.5-dimethylcyclohex-2-enylidene]malononitrile or OH1. Broadband THz radiation with a central frequency of 1.
View Article and Find Full Text PDFWe demonstrate a versatile tunable and highly stable ultrabroadband Ti:sapphire chirped pulse amplification system with a compressed pulse energy of 20 mJ at 100 Hz repetition rate. High power Ti:Sa systems in principle do not offer wavelength tunability due to gain narrowing. Here we demonstrate transform limited pulse generation from 15 fs to 94 fs with tunable central wavelength (λc from 755 nm to 845 nm) and bandwidth (130 nm<Δλ<16 nm) as well as multi-color, time synchronized, sub-100 fs pulses with user defined central wavelength separation.
View Article and Find Full Text PDFIn preparation for picosecond pump-probe experiments at the SwissFEL X-ray laser facility, the feasibility of collectively initiating surface chemical reactions using energetic pulses of terahertz radiation is being tested.
View Article and Find Full Text PDFPowerful THz radiation confined in one field period or less is an adequate tool for triggering nonlinear actions. We show results towards the realization of a tunable high-power THz source based on a laser-driven frequency conversion scheme in plasma and nonlinear crystals. A powerful THz source in combination with the future X-ray Free Electron Laser facility in Switzerland (SwissFEL) holds promise for exciting experiments in a variety of different research areas.
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