Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
  • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
  • H01S3/005—Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping
  • H01S3/0057—Temporal shaping, e.g. pulse compression, frequency chirping
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
  • B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
  • B23K26/06—Shaping the laser beam, e.g. by masks or multi-focusing
  • B23K26/062—Shaping the laser beam, e.g. by masks or multi-focusing by direct control of the laser beam
  • B23K26/0622—Shaping the laser beam, e.g. by masks or multi-focusing by direct control of the laser beam by shaping pulses
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
  • B23K26/352—Working by laser beam, e.g. welding, cutting or boring for surface treatment
  • B23K26/356—Working by laser beam, e.g. welding, cutting or boring for surface treatment by shock processing
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D10/00—Modifying the physical properties by methods other than heat treatment or deformation
  • C21D10/005—Modifying the physical properties by methods other than heat treatment or deformation by laser shock processing
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
  • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
  • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
  • H01S3/06—Construction or shape of active medium
  • H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
  • H01S3/067—Fibre lasers
  • H01S3/06754—Fibre amplifiers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
  • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
  • H01S3/09—Processes or apparatus for excitation, e.g. pumping
  • H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
  • H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
  • H01S3/094049—Guiding of the pump light
  • H01S3/094053—Fibre coupled pump, e.g. delivering pump light using a fibre or a fibre bundle
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
  • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
  • H01S3/23—Arrangements of two or more lasers not provided for in groups H01S3/02 - H01S3/22, e.g. tandem arrangements of separate active media
  • H01S3/2308—Amplifier arrangements, e.g. MOPA
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
  • H01S5/00—Semiconductor lasers
  • H01S5/02—Structural details or components not essential to laser action
  • H01S5/026—Monolithically integrated components, e.g. waveguides, monitoring photo-detectors, drivers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
  • H01S5/00—Semiconductor lasers
  • H01S5/50—Amplifier structures not provided for in groups H01S5/02 - H01S5/30
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
  • H01S2301/00—Functional characteristics
  • H01S2301/03—Suppression of nonlinear conversion, e.g. specific design to suppress for example stimulated brillouin scattering [SBS], mainly in optical fibres in combination with multimode pumping
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
  • H01S2301/00—Functional characteristics
  • H01S2301/20—Lasers with a special output beam profile or cross-section, e.g. non-Gaussian
  • H01S2301/206—Top hat profile
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
  • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
  • H01S3/005—Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
  • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
  • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
  • H01S3/06—Construction or shape of active medium
  • H01S3/0602—Crystal lasers or glass lasers
  • H01S3/061—Crystal lasers or glass lasers with elliptical or circular cross-section and elongated shape, e.g. rod
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
  • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
  • H01S3/09—Processes or apparatus for excitation, e.g. pumping
  • H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
  • H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
  • H01S3/094069—Multi-mode pumping
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
  • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
  • H01S3/09—Processes or apparatus for excitation, e.g. pumping
  • H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
  • H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
  • H01S3/094076—Pulsed or modulated pumping
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
  • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
  • H01S3/09—Processes or apparatus for excitation, e.g. pumping
  • H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
  • H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
  • H01S3/0941—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light of a laser diode
  • H01S3/09415—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light of a laser diode the pumping beam being parallel to the lasing mode of the pumped medium, e.g. end-pumping

Definitions

• high peak power means laser pulses having a peak power of the order of 10 MW or greater. Such pulses are adapted, after focusing on surfaces of a few mm 2 , typically between 0.1 and 10 mm 2 , to the generation of laser shocks in a given material, for example for laser shot blasting, surface cleaning, ultrasound generation, spectroscopy, etc.
• the light beam formed by said first laser pulses and incident on said reflective surface or surfaces has dimensions smaller than the dimensions of the one or more reflecting surfaces.
• the pump light source comprises for example a laser diode or a laser diode assembly
• the laser shock causes a vaporization of the surface to be treated.
• the ejected atoms and ions are carried into excited energy levels and emit, by de-excitation, a spectrum consisting of atomic lines, whose wavelength makes it possible to identify the elements present and whose intensity is proportional to the concentration of the emitting atoms.
• ablation cleaning the plasma created on the surface under the effect of the radiation relaxes, thus causing a splitting and an expulsion of the soil without damaging the surface to be cleaned.
• the system 10 When the system 10 is used for example for laser shot peening purposes, it is possible to provide also for the formation of the confinement layer, a water nozzle 14 fed by a water tank and a pump 12 delivering water. the water at the nozzle 14 by means of a pipe 13.
• the water is not obligatory and the confinement layer can equally well be obtained thanks to a gel, a paint or a solid material transparent to the length of the water.
• wave pulses eg Quartz
• the confinement layer is also not useful in applications other than laser shot blasting.
• the applicant has shown that it may be advantageous in a high peak laser pulse generation system according to the present description to reduce the DSP so as to be, for a given fiber diameter and a given length of the fiber device, below the stimulated Brillouin backscattering threshold in the fiber device.
• FIG. 3A is based on the use of an acousto-optic modulator 33 (MAO, or AOM), using the acousto-optical effect to diffract and change the optical frequency of light by sound waves (generally close to radio frequencies).
• MAO acousto-optic modulator 33
• AOM acousto-optic modulator 33
• FIG. 3B Another arrangement for multiplying the lines of the first laser pulses is shown in FIG. 3B.
• the incident pulses on the rotating mirror 42 have, for example, a spectrum So centered on an optical frequency v 0 and with a given spectral finesse (curve 401).
• the curve 402 schematically indicates the spatial distribution of the intensity I (r) of an incident pulse (fine line) and the spatial distribution of the optical frequency v (r) (thick line).
• the spatial distribution of the optical frequency is constant, for example equal to v 0 .
• the light beam formed by the incident laser pulses on each reflecting surface has a diameter less than or equal to:
• the light pulses can be reflected on each of the reflecting faces of the polygon and it is possible to multiply the spectral spreading effect by Doppler effect.
• the spectrum of a line incident on the rotating reflecting device will undergo a widening due to the Doppler effect expressed as follows:
• the beam undergoes a scan during its duration of 20 ns equal to 115 prad, or about 2 times the diffraction limit. . This will help to minimize the contrast of the speckle.
• the methods presented above for the reduction of PSD are not exhaustive and can be combined.
• the profile Po represents the profile of the intensity of the laser pulses emitted by a laser source, for example of the Gaussian type.
• the applicant has shown that with a profile Pi type "top hat", as shown in FIG. 5A, the risk of overcurrents during propagation in the fiber device is reduced.
• the spatial shaping of the beam in the image plane of the optical system 52 corresponds to the spatial Fourier transform of the phase mask imposed by the DOE 51 convolved with the spatial Fourier transform of the spatial intensity distribution of the beam at the level of the beam. DOE.
• the phase mask imposed by the DOE 51 is calculated such that the result of this convolution forms a "top hat" intensity distribution, the diameter D of the beam being proportional to the focal length f of the optical system 52.

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• Physics & Mathematics (AREA)
• Electromagnetism (AREA)
• Optics & Photonics (AREA)
• Engineering & Computer Science (AREA)
• Plasma & Fusion (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Condensed Matter Physics & Semiconductors (AREA)
• General Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Lasers (AREA)
• Optical Couplings Of Light Guides (AREA)

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• 2018
  • 2018-06-05 FR FR1854859A patent/FR3081737B1/fr active Active
• 2019
  • 2019-05-31 CN CN201980052366.4A patent/CN112544019A/zh active Pending
  • 2019-05-31 US US16/972,479 patent/US20210268605A1/en not_active Abandoned
  • 2019-05-31 WO PCT/EP2019/064219 patent/WO2019233899A1/fr not_active Ceased
  • 2019-05-31 JP JP2020568266A patent/JP2021525969A/ja active Pending
  • 2019-05-31 EP EP19731606.0A patent/EP3804052A1/de not_active Withdrawn

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