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We study optical field emission from silver nanotips, showing the combined influence of the illumination wavelength and the exact shape of the nanotip on the strong-field response. This is particularly relevant in the case of FIB milled nano tips, where the nanotip fabrication capabilities could become a new ingredient for the study of strong-field physics. The influence of the thermal load on the nanotip and its effect on the emission is studied as well by switching the repetition rate of the laser source from 1 kHz to 62 MHz, showing a clear transition towards the quenching of the strongfield emission.

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Bell's inequality violation experiments are becoming increasingly popular in the practical teaching of undergraduate and master's degree students. Bell's parameter S is obtained from 16 polarization correlation measurements performed on entangled photons pairs. We first report here a detailed analysis of the uncertainty u(S) of Bell's parameter taking into account coincidence count statistics and errors in polarizers' orientation. We show using both computational modeling and experimental measurement that the actual sequence of the polarizer settings has an unexpected and strong influence on the error budget. This result may also be relevant to measurements in other settings in which errors in parameters may have non-random effects in the measurement.

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We report results of experimental investigation of field electron emission from diamond nanoemitters. The measurements were performed with single crystal diamond needles fixed at tungsten tips. The voltage drop along diamond needles during emission was revealed and measured using electron energy spectroscopy. The observed linear dependence of the voltage drop in diamond on voltage applied to the tungsten tip is explained in the frame of a simple macroscopic electrical model combining Poole–Frenkel conduction along the diamond tip and Fowler–Nordheim tunneling at the diamond-vacuum junction. Experimental evidences of electron emission sensitivity to laser illumination are discussed for possible modification of diamond emitter characteristics and voltage drop.

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High-order harmonic generation in polyatomic molecules generally involves multiple channels of ionization. Their relative contribution can be strongly influenced by the presence of resonances, whose assignment remains a major challenge for high-harmonic spectroscopy. Here we present a multi-modal approach for the investigation of unaligned polyatomic molecules, using ​SF6 as an example. We combine methods from extreme-ultraviolet spectroscopy, above-threshold ionization and attosecond metrology. Fragment-resolved above-threshold ionization measurements reveal that strong-field ionization opens at least three channels. A shape resonance in one of them is found to dominate the signal in the 20–26 eV range. This resonance induces a phase jump in the harmonic emission, a switch in the polarization state and different dynamical responses to molecular vibrations. This study demonstrates a method for extending high-harmonic spectroscopy to polyatomic molecules, where complex attosecond dynamics are expected.

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Sujets

Time-resolved photoelectron spectroscopy Boîte quantique semiconductrice Chirp modulation rotational states quantum theory energy level crossing laser beams dissociation Pulse shaping Acétylène Atom-photon collisions ENERGY Autocorrelation function Oscillations de Rabi Photoémission NO2 Echantillon multidiffusant ELEMENTAL FRACTIONATION 4265Ky Interférences de chemins quantiques Quantum path interferences Couplage spatio-temporel XUV Gauss sums Champ fort Adiabatic rapid passage CYCLIC-N-3 7960Jv Cold Molecules Coherent pulse propagation Génération d'harmoniques d'ordre élevé Caractérisation spatio-temporelle Ultraviolet Femtosecond Femtoseconde Passage adiabatique rapide Extreme ultraviolet Attoseconde Rabi oscillations CHLORINE AZIDE 4230Kq Femtosecond lasers Number theory Femtosecond pulse CIN3 Anharmonicity Complete characterization Mise en forme d'impulsions Factorisation Photoemission Factorization Transitoires cohérents Rubidium atom Cold molecules Expériences pompe-sonde 7867Pt ALIGNED MOLECULES Cold field emission Femtosecond laser 4225Ja Bell's inequality Diamond nanotip Expérience pompe-sonde Coherent control Caractérisation Emission par champ froid Diffractive optical element ClN3 Mise en forme d'impulsion Dynamique moléculaire Femtochemistry Wave packet interferences Caractérisation complète Half revival Excited states sodium Impulsions à dérive de fréquence Quantum dots Femtosecond spectroscopy Coherent transients CHARGE-TRANSFER 4265Re Coherent Transients Contrôle cohérent Chlorine azide Femtosecond pulses Ultrashort pulses Pump-probe Attosecond Chirped pulses ATOMS Velocity map imaging Contrôle spatio-temporel Chirped laser pulses Quantum state measurement Ultrashort lasers C2H2 Coherent Transient Azoture de chlore Azulene Optical Parametric Amplifier AOPDF Spin-orbit precession Ultrafast nonlinear optics Characterisation Molecular dynamics

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Nombre de fichiers déposés

43

Nombre de notices déposées

79