Arnold Migus

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First Results of a Polychromatic Artificial Sodium Star for the Correction of Tilt

Adaptive Optics

With the present state of technology, the tilt component of a aberrated stellar wavefront which h... more With the present state of technology, the tilt component of a aberrated stellar wavefront which has been distorted by atmospheric turbulence cannot be ascertained by an artificial guide star. The absolute position of the artificial guide star cannot be determined since it wanders on the uplink portion of its propagation and there is no way, at least with a single receiving telescope, to distinguish an undetermined position of a guide star from tilt in the wavefront. In conventional adaptive optics systems, a natural star is needed to supply the tilt information in addition to the higher order corrections supplied by an artificial guide star. The probability of finding a suitably bright natural guide star for tilt correction is not significantly higher than for higher order correction despite the fact that the entire telescope area is used and both the tilt anisoplanatic angle and integration time are considerably larger. Since the tilt contributes ≈90% of the phase variance, the acc...

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High-power optical Stark effects in multiple-quantum-well structures

JOSAA, 1987

Laser Beam Shaping using Optically Addressed Spatial Light Modulators

Spatial Light Modulators and Intgrated Optoelectronic Arrays, 1999

We present the use of digital micromirror devices as variable illumination masks for pitch-splitt... more We present the use of digital micromirror devices as variable illumination masks for pitch-splitting multiple exposures to laser machine the surfaces of materials. Ultrafast laser pulses of length 150 fs and 800 nm central wavelength were used for the sequential machining of contiguous patterns on the surface of samples in order to build up complex structures with sub-diffraction limit features. Machined patterns of tens to hundreds of microns in lateral dimensions with feature separations as low as 270 nm were produced in electroless nickel on an optical setup diffraction-limited to 727 nm, showing a reduction factor below the Abbe diffraction limit of ~2.7x. This was compared to similar patterns in a photoresist optimised for two-photon absorption, which showed a reduction factor of only 2x, demonstrating that multiple exposures via ablation can produce a greater resolution enhancement than via two-photon polymerisation.

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Femtosecond And Subpicosecond Ultra-Intense Lasers

Laser Plasma Interactions 5, 2019

... A mathematical treatment using a four-dimensional Wigner function has been elaborated which t... more

High energy laser-pumped-Nd: Glass broadband regenerative amplifier at 1 Hz repetition rate

CLEO '97., Summaries of Papers Presented at the Conference on Lasers and Electro-Optics

plers. The laser threshold was determined to be 90 mW and 164 mW for these couplers, respectively... more plers. The laser threshold was determined to be 90 mW and 164 mW for these couplers, respectively. The slope efficiency of 37% and maximum output power of 360 mW at 1.29 W of absorbed pump power were obtained for 5% output coupler. From the slope efficiency data the double-pass passive loss value was estimated to be 1.1%. *Institut fur Laser-Physik, Universitiit Hamburg, Jungiusstr. 9a, 20355 Hamburg, Germany

Clôture : questions à deux philosophes, François Ewald (CNAM) et Jean Gayon (Université Paris 1)

Cloture : questions a deux philosophes, Francois Ewald (CNAM) et Jean Gayon (Universite Paris 1)

Ultrafast optical nonlinearities of CdSe quantum dots

In recent years, quantum confinement effects in semiconductor Systems with reduced space dimensio... more In recent years, quantum confinement effects in semiconductor Systems with reduced space dimensions have attracted considerable attention. Enhanced optical nonlinearities have been observed in multiple quantum wells and are predicted1−3 in quantum dots, i.e., semiconductor microstructures of a radius which is comparable to, or smaller than, the excitan Bohr radius in the corresponding bulk material. Semiconductor microcrystallites embedded in a glass matrix are an affordable alternative to study optical nonlinearities linked to finite size effects. This feature together with a rapid response time makes them attractive from the physics point of view and also for possible device applications.4

Rapport 21-06. Réformer la recherche en sciences biologiques et en santé : partie I, le financement

Bulletin de l'Académie Nationale de Médecine, 2021

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

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COVID-19 epidemic phases: Criteria, challenges and issues for the future

Bulletin de l'Académie Nationale de Médecine, 2020

Le meilleur moyen d'y parvenir est d'établir un diagnostic dans les cabinets médicaux, avec des d... more Le meilleur moyen d'y parvenir est d'établir un diagnostic dans les cabinets médicaux, avec des directives qui encouragent un dépistage généralisé et une couverture obligatoire pour les tests 9 Pour les US, la recommandation était de porter la capacité actuelle de 2,8 lits de soins intensifs pour 10 000 adultes à 5-7 lits pour 10 000 adultes en cas d'épidémie ou d'autre urgence, en tenant compte des variations régionales 10 Pour les US, la recommandation était de les porter de 3 pour 10 000 adultes à un objectif de 5 à 7 respirateurs pour 10 000. 11 Estimé pour les US à au moins 30 pour 10 000 adultes 12 Aux USA, les directives du CDC recommandent un isolement de sept jours. 13 Tels que définis par le CDC aux Etats-Unis

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Time-resolved spectroscopy with high-power tunable femtosecond pulses

Conference on Lasers and Electro-Optics, 1983

Spectral evidence for sub-picosecond iron displacement after ligand detachment from hemoproteins by femtosecond light pulses

The EMBO Journal, 1983

We have measured spectral and kinetic differences in protoheme, sperm whale or horse heart myoglo... more We have measured spectral and kinetic differences in protoheme, sperm whale or horse heart myoglobin and human hemoglobin following photodissociation induced by optical pulses of 80 fs duration. Full ligation was performed with oxygen or carbon monoxide. Femtosecond kinetics and transient difference spectra revealed the appearance of a deoxy species with r _ 250-300 fs. The transient deoxy species in myoglobin and hemoglobin evidenced a 3-4 nm red shift of their AA spectra compared with the equilibrium AA spectrum. This shift was not observed after photodissociation of the carbon monoxide liganded protoheme. We proposed that the 250 fs time constant corresponding to the appearance of the deoxy-like species is related to the displacement of the ferrous iron out of the heme plane. Consequently, the small red shift of the AA spectra observed in photodissociated hemoproteins may be tentatively attributed to changes in the vibrational modes of either the proximal histidine-Fe2+ bond and/or of the N4 porph-Fe-N. His (F8) bent.

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Evolution from perturbative to field-ionization regimes through electron spectroscopy

AIP Conference Proceedings, 1993

A study of the electron energy spectra from rare gases ionization by intense femtosecond pulses a... more A study of the electron energy spectra from rare gases ionization by intense femtosecond pulses allows to span the various ionization regimes in strong fields. Using 70 fs, 617 nm pulses, xenon, krypton, and argon produce electron energy spectra characteristic of the perturbative regime, i.e., dominated by resonances and Above-Threshold Ionization. However, for these atoms, ionization saturates at intensities lower

Energy Transfer during Silicon Irradiation by Femtosecond Laser Pulse

Physical Review Letters, 1984

Measurements of the total energy reflected from crystalline and amorphous silicon illuminated by ... more Measurements of the total energy reflected from crystalline and amorphous silicon illuminated by a femtosecond laser pulse are reported, for wavelengths of 0.62 and 0.31 p, m. The results are interpreted by use of a highly nonlinear regime of light propagation in the dense plasma of electrons and holes (e-h). Densities higher than 10'2 cm ' are reached. We demonstrate that free-carrier absorption is dominated by e-h collisions.

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Electron reactivity in aqueous media: A femtosecond investigation of the primary species

International Journal of Radiation Applications and Instrumentation. Part C. Radiation Physics and Chemistry, 1989

The electron is universally considered as a primary species in the radiolysis and photolysis of a... more The electron is universally considered as a primary species in the radiolysis and photolysis of aqueous media. The existence of this simplest aqueous radical implicates fascinating questions concerning the coupling of excess electrons with polar liquids whose chemical and physical properties may have a determinant influence on reactivity in chemistry and biology. The recent experimental results available from the femtosecond spectroscopy of water or ionic aqueous solutions provide unique experimental data for the elucidation of detailed mechanisms of mimary processes involved in electron reactivity with an essentially protic solvent.

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The LUCIA project: towards 100 joules nanosecond pulses, kW averaged power, based on ytterbium diode pumped solid state laser

Summaries of Papers Presented at the Lasers and Electro-Optics. CLEO '02. Technical Diges

The LUCIA (French acronym for &amp;amp;amp;amp;quot;Laser Ultra-Court Intenses, et Applicatio... more The LUCIA (French acronym for &amp;amp;amp;amp;quot;Laser Ultra-Court Intenses, et Applications&amp;amp;amp;amp;quot;) laser system consists in an oscillator delivering around 1 Joule in about 10 ns, followed by a multipass two-heads amplifier stage. In our design, oscillator and amplifier stages are longitudinally pumped at 10 Hz with respectively 15 and 10 kW/cm2 intensity with 1 ms pulses, allowing close to 20% optical

Generation of 220 fs, 352 nm pulse by high yield efficient frequency tripling of 1.06 μm, chirped pulses

Technical Digest. Summaries of papers presented at the Conference on Lasers and Electro-Optics. Postconference Edition. CLEO '99. Conference on Lasers and Electro-Optics (IEEE Cat. No.99CH37013)

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Efficient frequency tripling of 1.06 /spl mu/m, 300-fs chirped pulses

Technical Digest. Summaries of Papers Presented at the Conference on Lasers and Electro-Optics. Conference Edition. 1998 Technical Digest Series, Vol.6 (IEEE Cat. No.98CH36178), 1998

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Allocutions d'ouverture (Colloque "20 ans de la revue Hermès")

Statistics of th e hottest spot of spec kle pattern s gen erated by sm oothin g tec h nique s

Programmed analytical theory on the physical libration of the moon

The Moon and the Planets

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Arnold Migus

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