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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

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

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80