Commissariat &#xc0; L'&#xc9;nergie Atomique Et Aux &#xc9;nergies Alternatives

Fabien Quere

Gustave Pariente

Valentin Gallet

Antonin Borot

Subhendu Kahaly

Sylvain Monchoce

Henri Vincenti

A method for controlling the speed of a laser pulse includes a step of applying a chirp to the pulse; and a step of focusing the pulse by means of an optical system having a longitudinal chromatic aberration; whereby an intensity peak of the pulse moves along a propagation axis following, over a finite propagation length, a speed profile dependent on the chirp and on the longitudinal chromatic aberration. The use of such a method for accelerating particles via laser, and a system for implementing such a method, are also provided.

Method and system for controlling the speed of a laser pulse

A method for characterizing a light beam includes separating the light beam by a separator optic into first and second sub-beams; propagating the first and second sub-beams over first and second optics, respectively, said first and second optics being respectively arranged so that the sub-beams on leaving the optics are separated by a time delay &#x3c4;; recombining the sub-beams so that they spatially interfere and form a two-dimensional interference pattern; measuring the frequency spectrum of at least part of the interference pattern; calculating the Fourier transform in the time domain of at least one spatial point of the frequency spectrum, the Fourier transform in the time domain having a time central peak and first and second time side peaks; calculating the Fourier transform in the frequency domain for one of the side peaks; calculating the spectral amplitude A(&#x3c9;) and the spatial-spectral phase &#x3c6;(x,y,&#x3c9;) for the Fourier transform in the frequency domain.

Device and method for characterization of a light beam to determine the spatial-temporal properties of the light beam using a two dimensional interference pattern

A characterization method of a light beam includes separating the light beam into first and second sub-beams; propagating the first and second sub-beams over first and second optics respectively; the first sub-beam, which forms a reference beam, and the second sub-beam, which forms a characterized beam, being separated by a time delay &#x3c4;; recombining the reference and characterized beams so that they spatially interfere and form a two-dimensional interference pattern; measuring the pattern to obtain a temporal interferogram; calculating the Fourier transform in the frequency domain of a spatial point of the interferogram, the Fourier transform having a frequency central peak and first and second frequency side peaks; calculating the Fourier transform in the frequency domain for the first or second time side peaks calculating the spectral amplitude and the spatial-spectral phase for the first or second frequency side peak of the Fourier transform in the frequency domain.

Device and method for characterization of a light beam to determine space time couplings in the light beam using a two-dimensional interference pattern formed by the light beam and a fourier transform

Method of characterizing a light beam having the steps of: a) disposing the input ends of N &#x3e;3 optical fibers on the path of the light beam, in such a way that a respective portion of the beam is coupled and propagates in each optical fiber and is emitted from its output end so as to form a respective secondary beam; b) introducing an angular spectral dispersion into the secondary beams by means of at least one dispersive element; c) propagating the dispersed secondary beams in such a way that they overlap to form an interferogram; d) acquiring an image of the interferogram; and e) extracting from the image of the interferogram an item of information relating to the spatial variation of the phase of the light beam at a plurality of wavelengths. Device for the implementation of such a method.

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Vélizy-Villacoublay, France

Fabien Quere