Search results for "Picosecond"

160-GHz picosecond pulse train generation through multiwave mixing compression of a dual frequency beat signal

2002

We report the experimental generation and characterization of a 160-GHz picosecond puise train using multiple four-wave mixing temporal compression of an initial dual frequency beat signal in the anomalous-dispersion regime of a non-zero dispersion shifted fiber.

Evidence for metastable photo-induced superconductivity in K3C60

2021

Far and mid infrared optical pulses have been shown to induce non-equilibrium unconventional orders in complex materials, including photo-induced ferroelectricity in quantum paraelectrics, magnetic polarization in antiferromagnets and transient superconducting correlations in the normal state of cuprates and organic conductors. In the case of non-equilibrium superconductivity, femtosecond drives have generally resulted in electronic properties that disappear immediately after excitation, evidencing a state that lacks intrinsic rigidity. Here, we make use of a new optical device to drive metallic K$_3$C$_{60}$ with mid-infrared pulses of tunable duration, ranging between one picosecond and o…

Photon bunching of the nonlinear photoluminescence emitted by plasmonics metals

2021

International audience; In this report, we investigate the statistical temporal distribution of nonlinear upconverted photoluminescence emitted by gold and silver nanostructures excited by focused near-infrared laser pulses. We systematically observe a clear signature of photon bunching regardless of the nano-object's geometry, material's crystalline arrangement, and electronic band structure. The similarity of the data obtained across very different plasmonic objects confirms that these types of nonlinear radiation share a common chaotic origin and result from a collection of emitters. The correlation of photons at a picosecond time scale released by nanoscale nonlinear sources of broadban…

Rotational echoes as a tool for investigating ultrafast collisional dynamics of molecules

2019

We show that recently discovered rotational echoes of molecules provide an efficient tool for studying collisional molecular dynamics in high-pressure gases. Our study demonstrates that rotational echoes enable the observation of extremely fast collisional dissipation, at timescales of the order of a few picoseconds, and possibly shorter. The decay of the rotational alignment echoes in ${\mathrm{CO}}_{2}$ gas and ${\mathrm{CO}}_{2}\text{\ensuremath{-}}\mathrm{He}$ mixture up to 50 bar was studied experimentally, delivering collision rates that are in good agreement with the theoretical expectations. The suggested measurement protocol may be used in other high-density media, and potentially …

An Improved Double-Pulse Non-Normal Incidence Pumping Geometry for Transient Collisionally Excited Soft X-Ray Lasers

2009

An optimized pumping geometry for transient collisionally excited soft X-ray lasers is presented, similar to the geometry proposed by [1]. In contrast to usual approaches, where a nanosecond pre-pulse is assumed to provide the optimal plasma preparation and a picosecond pulse performs the final heating- and excitation process, two pulses of equal duration in the range around 10 picoseconds are applied. Both pulses are produced in the front end of the CPA pump laser. They are focused onto the target with the same spherical mirror under non-normal incidence geometry, optimized for efficient traveling wave excitation for the main-pulse. A first experiment was performed on Ni-like palladium (14…

Side-lobe suppression in electro-optic pulse generation

2007

A simple method is presented for rejecting undesirable tails and wings, around the main pulses of a periodic train, which is generated by electro-optical, sinusoidal phase modulation. It is shown that, by using a broadband optical carrier, the nonlinear chirp components generated by sinusoidal phase modulation can be filtered out. Thus, nearly apodised picosecond pulsation can be generated.

Acoustic dynamics of network-forming glasses at mesoscopic wavelengths

2013

The lack of long-range structural order in amorphous solids induces well known thermodynamic anomalies, which are the manifestation of distinct peculiarities in the vibrational spectrum. Although the impact of such anomalies vanishes in the long wavelength, elastic continuum limit, it dominates at length scales comparable to interatomic distances, implying an intermediate transition regime still poorly understood. Here we report a study of such mesoscopic domains by means of a broadband version of picosecond photo-acoustics, developed to coherently generate and detect hypersonic sound waves in the sub-THz region with unprecedented sampling efficiency. We identify a temperature-dependent fra…

Dynamical properties of water in living cells

2018

With the aim of studying the effect of water dynamics on the properties of biological systems, in this paper, we present a quasi-elastic neutron scattering study on three different types of living cells, differing both in their morphological and tumor properties. The measured scattering signal, which essentially originates from hydrogen atoms present in the investigated systems, has been analyzed using a global fitting strategy using an optimized theoretical model that considers various classes of hydrogen atoms and allows disentangling diffusive and rotational motions. The approach has been carefully validated by checking the reliability of the calculation of parameters and their 99% confi…

2015

AbstractLight absorption can trigger biologically relevant protein conformational changes. The light-induced structural rearrangement at the level of a photoexcited chromophore is known to occur in the femtosecond timescale and is expected to propagate through the protein as a quake-like intramolecular motion. Here we report direct experimental evidence of such ‘proteinquake’ observed in myoglobin through femtosecond X-ray solution scattering measurements performed at the Linac Coherent Light Source X-ray free-electron laser. An ultrafast increase of myoglobin radius of gyration occurs within 1 picosecond and is followed by a delayed protein expansion. As the system approaches equilibrium i…

Nonlinear refraction and absorption of spectrally tuneable picosecond pulses in carbon disulfide

2021

Abstract We analyze the spectral dependence of the nonlinear refractive index and nonlinear absorption coefficient of carbon disulfide (CS2) in the spectral range of 400–1100 nm using picosecond laser pulses. An increase of the nonlinear refractive index of CS2 at the shorter wavelength region compared with the near infrared region (9 × 10−14 cm2 W−1 (λ = 700 nm) and 4 × 10−14 cm2 W−1 (λ = 1000 nm), respectively) follows by a decrease of this parameter at the wavelengths below 600 nm. We compare the spectral dependences of the lower- and higher-order nonlinear absorption coefficients in carbon disulfide. The three-photon absorption coefficient was found to be maximal at λ = 1000 nm (β3PA = …