WO2024156721A1 - Device for generating stretched laser pulses with a modulated profile - Google Patents

Device for generating stretched laser pulses with a modulated profile Download PDF

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Publication number
WO2024156721A1
WO2024156721A1 PCT/EP2024/051581 EP2024051581W WO2024156721A1 WO 2024156721 A1 WO2024156721 A1 WO 2024156721A1 EP 2024051581 W EP2024051581 W EP 2024051581W WO 2024156721 A1 WO2024156721 A1 WO 2024156721A1
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WIPO (PCT)
Prior art keywords
pulse
component
laser
pulses
grouping
Prior art date
Application number
PCT/EP2024/051581
Other languages
French (fr)
Inventor
Julien Didierjean
Amélie CHERVET
Julien Saby
Marc CASTAING
Guillaume MACHINET
Original Assignee
Bloom Lasers
Alphanov
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Publication date
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Publication of WO2024156721A1 publication Critical patent/WO2024156721A1/en

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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
    • H01S5/00—Semiconductor lasers
    • H01S5/005—Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping
    • H01S5/0057—Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping for temporal shaping, e.g. pulse compression, frequency chirping
    • 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
    • H01S2301/08—Generation of pulses with special temporal shape or frequency spectrum
    • 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
    • H01S5/005—Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams 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
    • H01S5/00—Semiconductor lasers
    • H01S5/005—Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping
    • H01S5/0085—Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping for modulating the output, i.e. the laser beam is modulated outside the laser cavity
    • 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
    • H01S5/005—Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping
    • H01S5/0092—Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping for nonlinear frequency conversion, e.g. second harmonic generation [SHG] or sum- or difference-frequency generation outside the laser cavity
    • 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
    • H01S5/024—Arrangements for thermal management
    • 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
    • H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
    • H01S5/068—Stabilisation of laser output parameters
    • H01S5/06817—Noise reduction
    • 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
    • H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
    • H01S5/12—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region the resonator having a periodic structure, e.g. in distributed feedback [DFB] lasers

Definitions

  • the invention relates to the technical field of laser devices delivering short or ultra-short pulses, and more particularly pulses of fine spectrum less than a nanometer and of pulse duration from 100 picoseconds and up to durations of the order of nanoseconds.
  • the subject of the invention is a device for generating laser pulses with a duration of between 100 picoseconds up to durations of the order of a nanosecond, capable of adjusting the profile of said pulses; thus making it possible to have a flexible and adaptable pulse laser source according to the concrete needs of the application areas.
  • phase mode locking makes it possible, through a stretching system, to generate pulses in the range of interest, namely, more than 100 picoseconds and up to values of the order of nanoseconds; but does not allow controlling the temporal profile of the pulses.
  • this technique requires a complex stretching system and only works with relatively broad spectrum pulses, thus making the stretching of fine spectrum pulses, particularly of the order of 100 picometers, incompatible.
  • the invention is therefore placed in this context and seeks to resolve all of the aforementioned drawbacks.
  • the invention seeks to propose a device making it possible to generate, from a laser source delivering short pulses, laser pulses of duration greater than the duration of the pulses delivered by the source, in particular having a duration greater than 50 picoseconds , even greater than 100 picoseconds, or even greater than 10 nanoseconds; with control over the temporal profile of said pulses and with a potentially fine spectrum.
  • the invention relates to a light device emitting a laser pulse comprising:
  • a component for separating said initial pulse into two or more secondary pulses said separation component being arranged to transmit each of said secondary pulses to a dedicated propagation channel, each propagation channel being arranged to temporally offset the secondary pulse which propagates there for a given quantity of time, notably distinct from those of the other channels; • a power modulation component arranged to adjust the power of at least one of said secondary pulses according to a predetermined setpoint;
  • a pulse grouping component arranged to additively compose said offset and modulated secondary pulses into a single pulse, called the terminal pulse; said terminal pulse being a pulse of duration greater than the duration of the initial pulse.
  • the invention thus proposes to generate, from an initial pulse of duration Dl, a pulse of duration D2 greater than the duration of the initial pulse Dl by combining a set of secondary pulses offset in time and modulated in power so that the offset and modulation effects of each of the secondary pulses combine during the grouping of the shifted and modulated secondary pulses, in particular in power and/or in spectral characteristics, in order to obtain a terminal pulse having a profile predefined, as well as a duration greater than that of the initial pulse.
  • laser pulse means a brief period of light, in particular monochromatic and coherent, produced by a laser.
  • the term "spectrum" of a laser pulse is understood to mean the distribution of the energy of the pulse as a function of frequency, or equivalently, the distribution of the energy of the pulse depending on the wavelength.
  • frequency drift of a laser pulse is understood to mean a modification of the frequency of light over time within said pulse. Such frequency drift can be positive, negative or zero.
  • the term “profile” of a laser pulse is understood to mean the graph of the intensity, or a function of the latter, of said laser pulse over time.
  • the term “peak power” of a laser pulse means the maximum optical power that occurs.
  • the optical power of a laser being the quantity of energy emitted by the laser per unit of time.
  • the term “width at half height” of a laser pulse is understood to mean the duration during which its optical power is greater than half of its peak power.
  • interference noise means one or more unwanted interferences disrupting the temporal profile of the terminal pulse with regard to the desired profile.
  • the offset of the secondary pulses can be carried out by means of optical fibers of distinct lengths.
  • the travel time of the length of an optical fiber is directly proportional to the length of said fiber.
  • the different propagation channels can be made with distinct materials having their own refractive indices, so that the propagation time of a secondary pulse depends on the material constituting the propagation channel where said secondary pulse is propagates there, thus making it possible to properly shift the secondary pulses.
  • the propagation channels may be optical fibers made of glass, plastic or silica.
  • the separation component, the propagation channels, the modulation component and the grouping component are arranged so that the polarizations of the terminal pulse and the secondary pulses are identical to the polarization of the initial pulse, preferably linear.
  • the device according to the invention is arranged to maintain the polarization of the initial pulse until the composition of the terminal pulse.
  • one or more of the secondary pulses could be identical to the initial pulse. It is then understood that the separation component is not limited to the sole splitting of the initial pulse, but is capable of also generating replicas of said initial pulse.
  • the separation component is arranged to separate the initial pulse into several secondary pulses so as to preserve the spectrum of the initial pulse in each of the secondary pulses.
  • the grouping component may include planar or concave reflection mirrors, converging or diverging lenses, separator blades, optical fibers, components based on optical fibers such as fiber couplers.
  • the duration of the initial pulse is between 30 picoseconds and 70 picoseconds and the duration of the terminal pulse is greater than the length of the initial pulse, in particular between 100 picoseconds and 500 picoseconds.
  • the duration of the initial pulse is between 10 nanoseconds and 20 nanoseconds and the duration of the terminal pulse is greater than the length of the initial pulse, in particular between 50 nanoseconds and 500 nanoseconds.
  • the spectrum of the terminal pulse has a width at half maximum of less than 100 picometers.
  • the invention makes it possible in this case to start from this stretched pulse to generate a pulse of the order of a nanosecond, or even of of the order of ten nanoseconds with a controlled form, and thus to eliminate in particular undesirable effects such as the Brillouin effect in optical fibers.
  • the laser oscillator comprises a laser diode with distributed feedback.
  • this type of diode makes it possible to generate a transverse single-mode laser pulse and to obtain an output power of the order of mW.
  • This type of diode uses optical feedback making it possible to maintain a narrow spectral bandwidth. .
  • the laser oscillator comprises a mode-locked laser pulse source.
  • this type of pulse source makes it possible to generate pulses of very short duration, in particular of the order of a picosecond, and of high intensity.
  • the laser oscillator is arranged so that the laser pulse has a spectrum whose width at half maximum is less than 1 nanometer, in particular less than 100 picometers.
  • the laser oscillator is arranged so that the laser pulse emitted by said oscillator has a wavelength substantially of 1.5 micrometers, in particular of 1550 nanometers, or 2 micrometers, in particular 2100 nanometers.
  • the laser oscillator is arranged so that the laser pulse emitted by said oscillator has a wavelength substantially of 1030 nanometers or 1064 nanometers.
  • the laser pulses at these wavelengths can be converted efficiently, using non-linear processes, so as to generate pulses of wavelengths in the visible spectrum, in the infrared spectrum or in the ultraviolet spectrum, thus being suitable for their use in micromachining processes, in particular the micromachining of glass and silicon.
  • the wavelengths of 1030 nanometers and 1064 nanometers correspond to excitation lines of neodymium and ytterbium, particularly useful for micromachining using laser pulses of these wavelengths.
  • laser pulses whose wavelength is in the visible spectrum, in the near infrared or the mid infrared are particularly advantageous for the micromachining of plastic.
  • the laser oscillator is arranged so that the laser pulse emitted by said oscillator has a wavelength in the visible spectrum.
  • laser pulses whose wavelength is in the visible spectrum are particularly advantageous for the micromachining of plastic.
  • the laser pulses of wavelength 1030 nanometers and those of 1064 nanometers have the property of being slightly attenuated in the optical fibers which makes these wavelengths particularly interesting for preserving the power along of the path of the pulse within the device, in particular along the propagation channels.
  • the wavelengths of 1030 nanometers and 1064 nanometers are particularly desirable for micromachining, including cutting and modifying materials such as glass, metal, and plastic.
  • the light device comprises a controller of the laser oscillator, arranged to generate a control signal of said laser oscillator, said control signal being an instruction for generating said initial impulse.
  • the controller of the oscillator makes it possible to govern the generation of the pulses, in particular the rate of generation of the pulses and their intensity, and makes it possible to ensure the maintenance of the stability and precision of the frequency of the pulses.
  • the controller is arranged to generate a control signal defining a temporal profile of the initial pulse such that the additive composition, carried out by the grouping component, of the shifted secondary pulses and modulated is free from interference noise.
  • the suppression of the interference noise makes it possible to improve the profile and the stability of the terminal pulse.
  • the laser oscillator is arranged to generate a control signal comprising a first continuous component, in particular constant, and a second periodic and discontinuous component.
  • the combination of the continuous and periodic discontinuous components makes it possible to separate long and short term effects making it possible to optimize the operating parameters of the laser oscillator and the performances of the latter, in particular by adjusting the frequency and the amplitude of the periodic component.
  • the combination of the continuous and discontinuous periodic components makes it possible to synchronize the laser oscillator with other systems using the periodic component as a synchronization reference.
  • the propagation channels and the separation and grouping components are arranged so that the profiles of the shifted and modulated pulses overlap by at least 10% of their width at half height.
  • the laser oscillator is arranged so that the initial pulse includes a frequency drift during the duration of this pulse.
  • the device may comprise at least one optical component arranged to modify the frequency drift of a secondary pulse propagating in one of the propagation channels.
  • modifying the frequency drift of a secondary pulse offers an additional means of modulating the terminal pulse, resulting from the grouping of all the shifted and modulated secondary pulses.
  • the modification of the frequency drift of a secondary pulse could in particular be obtained by using diffraction gratings, prisms, dispersive fibers or Bragg gratings with variable pitch.
  • each transmission channel comprises at least one optical fiber.
  • the optical fibers generate a very low power loss and a low degradation of the laser pulse which propagates there, which makes it possible to effectively transmit said laser pulses over long distances.
  • the use of propagation channels made of optical fibers makes it possible to preserve the quality and power of the secondary pulses until the moment when the latter will be grouped by the grouping component.
  • optical fibers makes it possible to take advantage of their thinness and lightness as well as their flexibility making it possible to obtain propagation channels of various shapes.
  • the modulation component is arranged to adjust the power of at least one of said secondary pulses according to a gain or loss of power chosen so that the The terminal pulse has a predetermined profile.
  • the invention aims to use the power modulation of the im- secondary pulses which propagate in the propagation channels to control the shape of the time profile of the terminal pulse obtained during the additive composition of these secondary pulses. It will be understood that while the invention proposes to precisely control the temporal characteristics of the terminal pulse by modulating the power of the secondary pulses which propagate in the different propagation channels, this is obtained by modulating each secondary pulse according to a weighting established by the modulation component.
  • the modulation component and the separation component form the same optical element arranged to separate the initial pulse into two or more secondary pulses each having a predetermined distinct power and arranged to transmit each of said secondary pulses to a dedicated propagation channel.
  • this embodiment makes it possible to reduce the bulk of the device by combining the separation and modulation components previously mentioned in a single component.
  • At least one of the propagation channels comprises a power modulation component capable of adjusting the power of the secondary pulse which propagates there.
  • the fact of introducing the modulation component within one of the propagation channels makes it possible to carry out the modulation on any location of the channel, in particular at the start of the channel, in the middle of the channel or at the end of the channel. .
  • the power modulation component could in particular be arranged to increase or decrease the power of the secondary pulse on which it acts.
  • the propagation channel comprises several modulation components along the propagation channel.
  • the power modulation component could in particular be a passive optical component such as a partially reflective mirror, a section of optical fiber subjected to a mechanical disturbance, a partially reflective Bragg grating, a passive optical assembly such as an assembly “L/2 waveplate + polarizer” or an active component such as a liquid crystal modulator, an electro-optical modulator, an acousto-optical modulator or even a semiconductor modulator.
  • a passive optical component such as a partially reflective mirror, a section of optical fiber subjected to a mechanical disturbance, a partially reflective Bragg grating, a passive optical assembly such as an assembly “L/2 waveplate + polarizer” or an active component such as a liquid crystal modulator, an electro-optical modulator, an acousto-optical modulator or even a semiconductor modulator.
  • At least one of the propagation channels comprises an intensity filter of the secondary pulse which propagates there.
  • the intensity filter could be a saturable absorber, allowing progressive filtering of the secondary pulse and in particular capable of filtering the low intensities of the pulses and allowing the high intensities to pass.
  • the intensity filters could in particular be made of glass, ceramic or even nanomaterials in thin layers or in the form of nanoparticles based on semiconductors, doped or not, or even housings filled with chemical substances, in particular gas.
  • At least one of the propagation channels comprises a spectral filter.
  • a propagation channel comprising a spectral filter makes it possible to select a precise range of wavelengths of the secondary pulse which propagates there, in particular adapted to finely control the spectrum of the final pulse resulting from the grouping shifted and modulated secondary pulses.
  • the separation component, the propagation channels, the modulation component and the grouping component form a first optical stage of the device, so that a second optical stage comprises: a separation component, propagation channels, a modulation component and a grouping component, the second optical stage being connected in series with the first optical stage so that the separation component of the second optical stage receives the The terminal pulse composed by the grouping component of the first optical stage.
  • the first terminal pulse obtained by the first grouping component can be separated by the second separation component into several secondary pulses which will be modulated by the second modulation component before being grouped by the second grouping component of the second optical stage to thus generate a second terminal pulse.
  • the invention can include a number N of optical stages connected in a network and such that a terminal pulse of a given stage serves as an initial pulse of another stage.
  • the N stages could be arranged according to any network configuration, comprising all or part of the network in series and/or parallel connection.
  • the device makes it possible to modulate in phase and/or in amplitude the secondary pulses through at least one disturbing element of the propagation channels, particularly in the case propagation channels made from optical fibers.
  • This can be achieved by using a disturbing element which acts locally on the temperature, in particular a Peltier effect device, and/or which locally modifies the optical fiber mechanically, in particular a pressure means.
  • This ability to modulate secondary impulses allows for increased flexibility in applications where these pulses are used.
  • the device comprises an insulating enclosure capable of thermally and/or mechanically insulating one or more elements among: the separation component, the propagation channels, the modulation and the grouping component.
  • the insulating enclosure makes it possible to reduce the noise effects of the terminal pulse due to mechanical disturbances, in particular seismic, and/or external thermal, in particular radiative and/or convective. Furthermore, thermal insulation makes it possible to improve the quality of the terminal pulse by avoiding amplifying interference effects intrinsic to the device.
  • the insulating enclosure could in particular be made of heat-resistant materials, in particular aluminum and/or copper sheets or plates, ceramics such as alumina and silicon carbide or even ceramics. composite materials, particularly based on carbon fibers.
  • the insulating enclosure may in particular be made of pressure-resistant materials and may be designed to minimize vibrations and external shocks, in particular in rubber and/or foam, for example, in the form of pads or pads.
  • the invention also relates to an optical system, comprising a device according to the invention and at least one optical amplifier and/or a non-linear conversion system, capable of receiving the terminal pulse composed by the device.
  • the non-linear conversion system makes it possible to modify the wavelength of the terminal pulse, including in the case where the pulse has been amplified.
  • Said non-linear conversion system making it possible to modify the wavelength of the terminal pulse can in particular carry out frequency doubling.
  • FIG.1 represents, schematically and partially, a light device delivering a laser pulse according to one embodiment of the invention.
  • FIG.2 represents, schematically and partially, a time graph describing the typical profile of the initial laser pulse, according to one embodiment of the invention.
  • FIG.3 represents, schematically and partially, a time graph describing the typical profile of the terminal laser pulse, according to one embodiment of the invention.
  • FIG.4 represents, schematically and partially, a light device emitting a laser pulse and comprising two optical stages according to one embodiment of the invention.
  • a light device 6 emitting a laser pulse comprising:
  • a laser oscillator 1 emitting an initial pulse
  • a separation component 2 of the initial pulse into four secondary pulses; each of said secondary pulses is transmitted to a dedicated propagation channel 41, 42, 43, 44; each of said propagation channels is arranged to temporally shift the secondary pulse which propagates there for a given quantity of time;
  • a grouping component 5 arranged to additively compose said offset and modulated secondary pulses into a single terminal pulse; said terminal pulse being a laser pulse of duration greater than the duration of the initial pulse.
  • the laser oscillator 1 comprises a laser diode with distributed feedback.
  • the laser oscillator 1 may alternatively include a source of mode-locked laser pulses.
  • the laser oscillator 1 is arranged so as to emit a laser pulse with a wavelength substantially equal to 1030 nm.
  • the emission wavelength could be substantially equal to 1064 nm.
  • the light device 6 comprises a controller of the laser oscillator 1 (not shown) arranged to generate a control signal of said laser oscillator 1, said control signal being an instruction for generating the initial pulse.
  • the controller of the laser oscillator (not shown) is arranged to generate a control signal defining a profile of the initial pulse such that the additive composition, by the grouping component 5, of the shifted and modulated secondary pulses is free from interference noise.
  • the controller of the laser oscillator (not shown) is also arranged to generate a control signal comprising a first continuous component, in particular constant, and a second periodic and discontinuous component.
  • the propagation channels 41, 42, 43, 44 and the separation components 2 and grouping components 5 are arranged so that the profiles of the shifted and modulated pulses overlap by at least 10% of their width at midpoint. height.
  • the laser oscillator 1 is arranged so that the initial pulse includes a frequency drift during the duration of this pulse.
  • the device 6 comprises at least one optical component (not shown) arranged to modify the frequency drift of a secondary pulse propagating in one of the propagation channels 41, 42, 43, 44.
  • Each transmission channel 41, 42, 43, 44 comprises at least one optical fiber.
  • the modulation components 31, 32, 33, 34 are arranged to adjust the power of at least one of the secondary pulses according to a power gain or loss chosen so that the terminal pulse has a predetermined profile .
  • the propagation channels 41, 42, 43, 44 include an intensity filter (not shown) of the secondary pulse which propagates there.
  • the propagation channels 41, 42, 43, 44 include a spectral filter (not shown) of the secondary pulse which propagates there.
  • the device comprises an insulating enclosure (not shown) capable of thermally and/or mechanically insulating the separation 2, modulation 31, 32, 33, 34 and grouping 5 components.
  • the time graph describing the typical profile of the initial laser pulse is shown in [Fig.2], according to one embodiment of the invention.
  • the pulse profile can notably take the form of a Gaussian distribution, a hyperbolic secant, or more generally a Gumbel or Weibull distribution.
  • the profile of the initial pulse has a duration at half height of approximately 50 picoseconds and has a rising edge with a slope significantly lower than that of the falling edge.
  • This typical profile corresponds to the profile of a laser pulse emitted by the laser oscillator 1 and has a wavelength substantially of 1030 nanometers according to one embodiment of the invention or of 1064 nanometers according to another mode of realization.
  • the profile of the terminal pulse in [Fig.3] is obtained after grouping, by the grouping component 5, 501, 502, the secondary pulses shifted and modulated by the separation component 2, 201, 202 and the modulation component 31, 32, 33, 34, 301, 302, 303, 304. It is notable that the profile of the terminal pulse in [Fig.3] does not include interference noise and is of the form substantially similar to a square pulse of 180 picoseconds duration, duration notably greater than the duration of the initial pulse represented in [Fig.2].
  • the profile of the terminal pulse of [Fig.3] resulting from the additive composition by the grouping component 5, 501, 502 of the shifted and modulated secondary pulses is devoid of interference noise due to the fact that, d
  • the controller of the laser oscillator (not shown) is arranged for this purpose, and on the other hand the initial pulse has a frequency drift which limits the coherence of the secondary pulses shifted in time.
  • the separation component 201, the propagation channels (not shown), the modulation components 301, 302 and the grouping component 501 form a first optical stage of the device, so that a second optical stage comprises a component separation 202, propagation channels (not shown), two modulation components 303, 304 and a grouping component 502, the second optical stage being connected in series with the first optical stage so that the separation component 202 of the second optical stage receives the terminal pulse composed by the grouping component 501 of the first optical stage.
  • the light device in [Fig.4] also includes a receiver 600 of the terminal pulse.
  • the device comprises an insulating enclosure (not shown) capable of thermally and/or mechanically insulating the separation components 201, 202, modulation 301, 302, 303, 304 and grouping 501, 502.
  • the invention cannot be limited to the specific embodiments fically described in this document, and extends in particular to all equivalent means and to any technically effective combination of these means.

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  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Optics & Photonics (AREA)
  • Lasers (AREA)
  • Semiconductor Lasers (AREA)

Abstract

The invention relates to a lighting device (6) emitting a laser pulse, comprising: - a laser oscillator (1) emitting a laser pulse, referred to as initial pulse; - a splitter component (2) for splitting said initial pulse into two or more secondary pulses, said splitter component being designed to transmit each of said secondary pulses to a dedicated propagation channel (41, 42, 43, 44), each propagation channel (41, 42, 43, 44) being designed to time-shift the secondary pulse propagating therein by a given amount of time, in particular distinct from those of the other channels; - a power modulation component (31, 32, 33, 34, 301, 302, 303, 304) designed to adjust the power of at least one of said secondary pulses in accordance with a predetermined setpoint; a pulse grouping component (5, 501, 502) designed to add together said shifted and modulated secondary pulses into one and the same pulse, referred to as final pulse; said final pulse being a laser pulse with a duration greater than the duration of the initial pulse.

Description

Description Description
Titre de l'invention : Dispositif de génération d’impulsions laser étirées à profil modulé Title of the invention: Device for generating stretched laser pulses with modulated profile
Domaine technique. Technical area.
[0001] L’invention se rapporte au domaine technique des dispositifs lasers délivrant des impulsions courtes ou ultra-courtes, et plus particulièrement des impulsions de spectre fin inférieur au nanomètre et de durée d’impulsion à partir de 100 picosecondes et jusqu’à des durées de l’ordre de la nanoseconde. [0001] The invention relates to the technical field of laser devices delivering short or ultra-short pulses, and more particularly pulses of fine spectrum less than a nanometer and of pulse duration from 100 picoseconds and up to durations of the order of nanoseconds.
[0002] L’invention a pour objet un dispositif de génération d’impulsions laser de durée comprise entre 100 picosecondes jusqu’à des durées de l’ordre de la nanoseconde, capable d’ajuster le profil desdites impulsions ; permettant ainsi de disposer d'une source laser impulsionnelle flexible et adaptable en fonction des besoins concrets des domaines d’application. [0002] The subject of the invention is a device for generating laser pulses with a duration of between 100 picoseconds up to durations of the order of a nanosecond, capable of adjusting the profile of said pulses; thus making it possible to have a flexible and adaptable pulse laser source according to the concrete needs of the application areas.
État de la technique. State of the art.
[0003] La génération d'impulsions laser dans la gamme de 100 picosecondes à 500 picosecondes de durée et présentant un profil ajustable est un défi technologique majeur. En effet, d’une part il est difficile d'obtenir, à partir des méthodes de génération d’impulsions couramment mises en œuvre, des impulsions laser de cette durée, tout en parvenant à régler de manière fine le profil temporel des impulsions, ; notamment celles ayant recours à des lasers déclenchés, des lasers à modulation externe ou encore des lasers à semi-conducteurs modulés en courant. Dès lors, ces méthodes de génération d’impulsions laser ne permettent pas d'atteindre cette gamme de durée d'impulsions ni de contrôler précisément la forme temporelle desdites impulsions. [0003] The generation of laser pulses in the range of 100 picoseconds to 500 picoseconds in duration and having an adjustable profile is a major technological challenge. Indeed, on the one hand it is difficult to obtain, using pulse generation methods currently used, laser pulses of this duration, while managing to finely adjust the temporal profile of the pulses; in particular those using triggered lasers, externally modulated lasers or even current modulated semiconductor lasers. Therefore, these methods of generating laser pulses do not make it possible to reach this range of pulse duration nor to precisely control the temporal shape of said pulses.
[0004] La technique dite de « verrouillage des modes en phase » permet, au travers d’un système d’étirement, de générer des impulsions dans la gamme d’intérêt, à savoir, de plus de 100 picosecondes et jusqu’à des valeurs de l’ordre de la nanoseconde ; mais ne permet pas contrôler le profil temporel des impulsions. De plus, cette technique nécessite un système d’étirement complexe et ne fonctionne qu’avec des impulsions de spectre relativement large, rendant ainsi incompatible l’étirement d’impulsions à spectre fin, notamment de l’ordre de 100 picomètres. [0004] The so-called “phase mode locking” technique makes it possible, through a stretching system, to generate pulses in the range of interest, namely, more than 100 picoseconds and up to values of the order of nanoseconds; but does not allow controlling the temporal profile of the pulses. In addition, this technique requires a complex stretching system and only works with relatively broad spectrum pulses, thus making the stretching of fine spectrum pulses, particularly of the order of 100 picometers, incompatible.
[0005] La génération d'impulsions par commutation de gain d’une diode laser tend généralement à produire des impulsions plus courtes mais il est difficile de concevoir une diode laser spécifiquement pour obtenir des impulsions aussi longues ; de plus, le phénomène physique de commutation du gain ne permet pas de contrôler la forme temporelle des impulsions ni les phases desdites impulsions. [0005] The generation of pulses by switching the gain of a laser diode generally tends to produce shorter pulses but it is difficult to design a laser diode specifically to obtain such long pulses; moreover, the physical phenomenon of gain switching does not make it possible to control the temporal shape of the pulses nor the phases of said pulses.
[0006] En outre, certaines applications nécessitant des impulsions laser dans cette gamme de durée requièrent également une longueur d’onde laser dans le spectre visible ou dans le spectre ultraviolet. Ces longueurs d’onde sont généralement atteintes en partant d’une impulsion laser infrarouge, notamment de longueur d’onde autour de 1 micromètre, et en utilisant des cristaux non-linéaires pour effectuer une conversion de la longueur d'onde. Cependant, les accords de phase réalisés dans ces cristaux non-linéaires pour ces conversions ont une acceptance spectrale limitée, ce qui peut être problématique lorsque le spectre de la source laser est trop large. Dès lors, il est souvent nécessaire de disposer d'une source laser à spectre fin, typiquement inférieure à 100 picomètres de largeur spectrale à mi-hauteur, pour pouvoir utiliser efficacement des cristaux non- linéaires pour la génération d'impulsions de l'ordre de 100 picosecondes à 500 picosecondes. [0006] Furthermore, certain applications requiring laser pulses in this range of duration also require a laser wavelength in the visible spectrum or in the ultraviolet spectrum. These wavelengths are generally achieved by starting from an infrared laser pulse, in particular with a wavelength around 1 micrometer, and by using non-linear crystals to carry out a conversion of the wavelength. However, the phase matches made in these non-linear crystals for these conversions have a limited spectral acceptance, which can be problematic when the spectrum of the laser source is too broad. Therefore, it is often necessary to have a fine-spectrum laser source, typically less than 100 picometers of spectral width at half maximum, to be able to effectively use non-linear crystals for the generation of pulses of the order from 100 picoseconds to 500 picoseconds.
[0007] Il est connu que le profil d’une impulsion laser peut avoir un impact important sur son interaction avec la matière, déterminant ainsi les applications pour lesquelles l’impulsion pourra être utilisée. Il existe de nombreux types de profils d’impulsions lasers, tels que les impulsions de profil temporel carré, gaussien, ou plus complexe avec des fronts de montée et de descente lents ou rapides. [0007] It is known that the profile of a laser pulse can have a significant impact on its interaction with the material, thus determining the applications for which the pulse can be used. There are many types of laser pulse profiles, such as square, Gaussian, or more complex time profile pulses with slow or fast rising and falling edges.
[0008] Il est possible de générer des impulsions lasers très courtes présentant un profil carré par des modulateurs électrooptiques, néanmoins ce type de dispositif ont des coût très élevés et ne permettent pas d’ajuster la forme de l’impulsion. [0008] It is possible to generate very short laser pulses having a square profile by electro-optical modulators, however this type of device has very high costs and does not allow the shape of the pulse to be adjusted.
[0009] On peut noter à titre d’exemple que la génération d'impulsions carrées est particulièrement utile pour maximiser l'efficacité des conversions non linéaires. [0009] It can be noted by way of example that the generation of square pulses is particularly useful for maximizing the efficiency of nonlinear conversions.
[0010] L’invention se place donc dans ce contexte et cherche à résoudre l’ensemble des inconvénients précités. Ainsi, l’invention cherche à proposer un dispositif permettant de générer, à partir d’une source laser délivrant des impulsions courtes, des impulsions laser de durée supérieure à la durée des impulsions délivrées par la source, notamment ayant une durée supérieure à 50 picosecondes, voire supérieure à 100 picosecondes, voire supérieure à 10 nanosecondes; avec un contrôle sur le profil temporel desdites impulsions et avec un spectre potentiellement fin. [0010] The invention is therefore placed in this context and seeks to resolve all of the aforementioned drawbacks. Thus, the invention seeks to propose a device making it possible to generate, from a laser source delivering short pulses, laser pulses of duration greater than the duration of the pulses delivered by the source, in particular having a duration greater than 50 picoseconds , even greater than 100 picoseconds, or even greater than 10 nanoseconds; with control over the temporal profile of said pulses and with a potentially fine spectrum.
Présentation de l’invention. Presentation of the invention.
[0011] A ces fins, l’invention a pour objet un dispositif lumineux émettant une impulsion laser comportant : [0011] For these purposes, the invention relates to a light device emitting a laser pulse comprising:
• un oscillateur laser émettant une impulsion laser, dit impulsion initiale ; • a laser oscillator emitting a laser pulse, called the initial pulse;
• un composant de séparation de ladite impulsion initiale en deux ou plusieurs impulsions secondaires, ledit composant de séparation étant agencé pour transmettre chacune desdites impulsions secondaires vers un canal de propagation dédié, chaque canal de propagation étant agencé pour décaler tempo- rellement l’impulsion secondaire qui s’y propage d’une quantité de temps donnée, notamment distincte de celles des autres canaux ; • un composant de modulation de puissance agencé pour ajuster la puissance d’au moins l’une desdites impulsions secondaires selon une consigne prédéterminée ; • a component for separating said initial pulse into two or more secondary pulses, said separation component being arranged to transmit each of said secondary pulses to a dedicated propagation channel, each propagation channel being arranged to temporally offset the secondary pulse which propagates there for a given quantity of time, notably distinct from those of the other channels; • a power modulation component arranged to adjust the power of at least one of said secondary pulses according to a predetermined setpoint;
• un composant de regroupement d’impulsions agencé pour composer addi- tivement lesdites impulsions secondaires décalées et modulées en une seule et même impulsion, dite impulsion terminale ; ladite impulsion terminale étant une impulsion de durée supérieure à la durée de l’impulsion initiale. • a pulse grouping component arranged to additively compose said offset and modulated secondary pulses into a single pulse, called the terminal pulse; said terminal pulse being a pulse of duration greater than the duration of the initial pulse.
[0012] L’invention propose ainsi de générer, à partir d’une impulsion initiale de durée Dl, une impulsion de durée D2 supérieure à la durée de l’impulsion initiale Dl en combinant un ensemble d’impulsions secondaires décalées dans le temps et modulées en puissance de sorte que les effets de décalage et de modulation de chacune des impulsions secondaires se combinent lors du regroupement des impulsions secondaires décalées et modulées, notamment en puissance et/ou en caractéristiques spectrales, afin d’obtenir une impulsion terminale présentant un profil prédéfini, ainsi qu’une durée supérieure à celle de l’impulsion initiale. [0012] The invention thus proposes to generate, from an initial pulse of duration Dl, a pulse of duration D2 greater than the duration of the initial pulse Dl by combining a set of secondary pulses offset in time and modulated in power so that the offset and modulation effects of each of the secondary pulses combine during the grouping of the shifted and modulated secondary pulses, in particular in power and/or in spectral characteristics, in order to obtain a terminal pulse having a profile predefined, as well as a duration greater than that of the initial pulse.
[0013] Dans la présente invention, on entend par « impulsion laser » une brève période de lumière, notamment monochromatique et cohérente, produite par un laser. [0013] In the present invention, the term “laser pulse” means a brief period of light, in particular monochromatic and coherent, produced by a laser.
[0014] Dans la présente invention, on entend par « spectre » d’une impulsion laser la distribution de l’énergie de l’impulsion en fonction de la fréquence, ou de manière équivalente, la distribution de l’énergie de l’impulsion en fonction de la longueur d’onde. [0014] In the present invention, the term "spectrum" of a laser pulse is understood to mean the distribution of the energy of the pulse as a function of frequency, or equivalently, the distribution of the energy of the pulse depending on the wavelength.
[0015] Dans la présente invention, on entend par « dérive de fréquence » d’une impulsion laser une modification de la fréquence de lumière au cours du temps au sein de ladite impulsion. Une telle dérive de fréquence peut être positive, négative ou nulle. [0015] In the present invention, the term “frequency drift” of a laser pulse is understood to mean a modification of the frequency of light over time within said pulse. Such frequency drift can be positive, negative or zero.
[0016] Dans la présente invention, on entend par « profil » d’une impulsion laser le graphe de l’intensité, ou une fonction de cette dernière, de ladite impulsion laser au cours du temps. [0016] In the present invention, the term “profile” of a laser pulse is understood to mean the graph of the intensity, or a function of the latter, of said laser pulse over time.
[0017] Dans la présente invention, on entend par « puissance crête » d’une impulsion laser, la puissance optique maximale qui se produit. La puissance optique d’un laser étant la quantité d’énergie émise par le laser par unité de temps. [0017] In the present invention, the term “peak power” of a laser pulse means the maximum optical power that occurs. The optical power of a laser being the quantity of energy emitted by the laser per unit of time.
[0018] Dans la présente invention, on entend par « largeur à mi-hauteur » d’une impulsion laser la durée au cours de laquelle sa puissance optique est supérieure à la moitié de sa puissance crête. [0018] In the present invention, the term “width at half height” of a laser pulse is understood to mean the duration during which its optical power is greater than half of its peak power.
[0019] Dans la présente invention, on entend par « bruit d’interférence » une ou plusieurs interférences non souhaitées venant perturber le profil temporel de l’impulsion terminale au regard du profil souhaité. [0019] In the present invention, the term “interference noise” means one or more unwanted interferences disrupting the temporal profile of the terminal pulse with regard to the desired profile.
[0020] Avantageusement, le décalage des impulsions secondaires peut être réalisé au moyen de fibres optiques de longueur distinctes. En effet, le temps de parcours de la longueur d’une fibre optique est directement proportionnel à la longueur de ladite fibre. Advantageously, the offset of the secondary pulses can be carried out by means of optical fibers of distinct lengths. In fact, the travel time of the length of an optical fiber is directly proportional to the length of said fiber.
[0021] Avantageusement encore, les différents canaux de propagation pourront être réalisés avec des matériaux distincts présentant des indices de réfractions propres, de sorte que le temps de propagation d’une impulsion secondaire dépende du matériau constituant le canal de propagation où ladite impulsion secondaire s’y propage, permettant ainsi de décaler convenablement les impulsions secondaires. [0021] Advantageously, the different propagation channels can be made with distinct materials having their own refractive indices, so that the propagation time of a secondary pulse depends on the material constituting the propagation channel where said secondary pulse is propagates there, thus making it possible to properly shift the secondary pulses.
[0022] De préférence, les canaux de propagation pourront être des fibres optiques réalisées en verre, plastique ou silice. Preferably, the propagation channels may be optical fibers made of glass, plastic or silica.
[0023] Avantageusement, le composant de séparation, les canaux de propagation, le composant de modulation et le composant de regroupement sont agencés pour que les polarisations de l’impulsion terminale et des impulsions secondaires soient identiques à la polarisation de l’impulsion initiale, préférentiellement linéaire. En d’autres termes, le dispositif selon l’invention est agencé pour conserver la polarisation de l’impulsion initiale jusqu’à la composition de l’impulsion terminale. Advantageously, the separation component, the propagation channels, the modulation component and the grouping component are arranged so that the polarizations of the terminal pulse and the secondary pulses are identical to the polarization of the initial pulse, preferably linear. In other words, the device according to the invention is arranged to maintain the polarization of the initial pulse until the composition of the terminal pulse.
[0024] Si on le souhaite, une ou plusieurs des impulsions secondaires pourront être identiques à l’impulsion initiale. On comprend alors que le composant de séparation n’est pas limité au seul fractionnement de l’impulsion initiale, mais est apte à générer également des répliques de ladite impulsion initiale. If desired, one or more of the secondary pulses could be identical to the initial pulse. It is then understood that the separation component is not limited to the sole splitting of the initial pulse, but is capable of also generating replicas of said initial pulse.
[0025] Avantageusement, le composant de séparation est agencé pour séparer l’impulsion initiale en plusieurs impulsions secondaires de manière à conserver le spectre de l’impulsion initiale dans chacune des impulsions secondaires. Advantageously, the separation component is arranged to separate the initial pulse into several secondary pulses so as to preserve the spectrum of the initial pulse in each of the secondary pulses.
[0026] Avantageusement, le composant de regroupement pourra comporter des miroirs de réflexion plans ou concaves, des lentilles convergentes ou divergentes, des lames séparatrices, des fibres optiques, des composants à base de fibres optiques tels que des coupleurs fibrés. Advantageously, the grouping component may include planar or concave reflection mirrors, converging or diverging lenses, separator blades, optical fibers, components based on optical fibers such as fiber couplers.
[0027] Avantageusement, la durée de l’impulsion initiale est comprise entre 30 picosecondes et 70 picosecondes et la durée de l’impulsion terminale est supérieure à la longueur de l’impulsion initiale, notamment comprise entre 100 picosecondes et 500 picosecondes. Advantageously, the duration of the initial pulse is between 30 picoseconds and 70 picoseconds and the duration of the terminal pulse is greater than the length of the initial pulse, in particular between 100 picoseconds and 500 picoseconds.
[0028] Avantageusement, la durée de l’impulsion initiale est comprise entre 10 nanosecondes et 20 nanosecondes et la durée de l’impulsion terminale est supérieure à la longueur de l’impulsion initiale, notamment comprise entre 50 nanosecondes et 500 nanosecondes. Advantageously, the duration of the initial pulse is between 10 nanoseconds and 20 nanoseconds and the duration of the terminal pulse is greater than the length of the initial pulse, in particular between 50 nanoseconds and 500 nanoseconds.
[0029] Avantageusement, le spectre de l’impulsion terminale a une largeur à mi-hauteur inférieure à 100 picomètres. En procédant ainsi, la conversion des longueurs d’onde dans des cristaux non-linéaires est réalisée efficacement. Advantageously, the spectrum of the terminal pulse has a width at half maximum of less than 100 picometers. By doing this, the conversion of wavelengths in nonlinear crystals is carried out efficiently.
[0030] Si on le souhaite, en partant d’une source laser à spectre large, notamment un oscillateur à mode verrouillé en phase, émettant des impulsions de l’ordre de 1 picoseconde et dont le spectre à une largeur de plusieurs nanomètres, il est possible d’étirer ladite impulsion par dérive de fréquence pour arriver à des durées d’impulsions de quelques centaines de picosecondes, l’invention permet dans ce cas de partir de cette impulsion étirée pour générer une impulsion de l’ordre de la nanoseconde, voire de l’ordre de la dizaine de nanoseconde avec une forme contrôlée, et ainsi de supprimer notamment des effets indésirables tels que l’effet Brillouin dans les fibres optiques. If desired, starting from a broad-spectrum laser source, in particular a phase-locked mode oscillator, emitting pulses of the order of 1 picosecond and whose spectrum has a width of several nanometers, it is possible to stretch said pulse by frequency drift to arrive at pulse durations of a few hundred picoseconds, the invention makes it possible in this case to start from this stretched pulse to generate a pulse of the order of a nanosecond, or even of of the order of ten nanoseconds with a controlled form, and thus to eliminate in particular undesirable effects such as the Brillouin effect in optical fibers.
Modes de réalisation de l’invention Modes of carrying out the invention
[0031] Dans un mode de réalisation de l’invention, l’oscillateur laser comprend une diode laser à rétroaction répartie. [0031] In one embodiment of the invention, the laser oscillator comprises a laser diode with distributed feedback.
[0032] Avantageusement, ce type de diode permet de générer une impulsion laser monomode transverse et d’obtenir une puissance de sortie de l’ordre du mW ce type de diode a recours à une rétroaction optique permettant de maintenir une largeur de bande spectrale étroite. [0032] Advantageously, this type of diode makes it possible to generate a transverse single-mode laser pulse and to obtain an output power of the order of mW. This type of diode uses optical feedback making it possible to maintain a narrow spectral bandwidth. .
[0033] Dans un mode de réalisation alternatif de l’invention, l’oscillateur laser comprend une source d’impulsions laser à verrouillage de mode. [0033] In an alternative embodiment of the invention, the laser oscillator comprises a mode-locked laser pulse source.
[0034] Avantageusement, ce type de source d’impulsions permet de générer des impulsions de très courte durée, notamment de l’ordre de la picoseconde, et de forte intensité. Advantageously, this type of pulse source makes it possible to generate pulses of very short duration, in particular of the order of a picosecond, and of high intensity.
[0035] Dans un mode de réalisation de l’invention, l’oscillateur laser est agencé de sorte que l’impulsion laser présente un spectre dont la largeur à mi-hauteur est inférieure à 1 nanomètre, notamment inférieur à 100 picomètres. [0035] In one embodiment of the invention, the laser oscillator is arranged so that the laser pulse has a spectrum whose width at half maximum is less than 1 nanometer, in particular less than 100 picometers.
[0036] Dans un mode de réalisation de l’invention, alternatif ou cumulatif, l’oscillateur laser est agencé de sorte que l’impulsion laser émise par ledit oscillateur présente une longueur d’onde sensiblement de 1,5 micromètres, notamment de 1550 nanomètres, ou de 2 micromètres, notamment de 2100 nanomètres. [0036] In an alternative or cumulative embodiment of the invention, the laser oscillator is arranged so that the laser pulse emitted by said oscillator has a wavelength substantially of 1.5 micrometers, in particular of 1550 nanometers, or 2 micrometers, in particular 2100 nanometers.
[0037] Dans un autre mode de réalisation de l’invention, alternatif ou cumulatif, l’oscillateur laser est agencé de sorte que l’impulsion laser émise par ledit oscillateur présente une longueur d’onde sensiblement de 1030 nanomètres ou 1064 nanomètres. [0037] In another embodiment of the invention, alternative or cumulative, the laser oscillator is arranged so that the laser pulse emitted by said oscillator has a wavelength substantially of 1030 nanometers or 1064 nanometers.
[0038] Avantageusement, les impulsions laser à ces longueurs d’onde peuvent être converties efficacement, grâce à des processus non-linéaires, de sorte à générer des impulsions de longueurs d’onde dans le spectre visible, dans le spectre infrarouge ou dans le spectre ultraviolet, étant ainsi appropriés pour leur utilisation dans des procédés de micro-usinage, en particulier le micro-usinage du verre et du silicium. Par ailleurs, les longueurs d’onde de 1030 nanomètres et de 1064 nanomètres correspondent à des raies d’excitation du néodyme et de l’ytterbium, particulièrement utiles pour le microusinage par des impulsions laser de ces longueurs d’onde. [0038] Advantageously, the laser pulses at these wavelengths can be converted efficiently, using non-linear processes, so as to generate pulses of wavelengths in the visible spectrum, in the infrared spectrum or in the ultraviolet spectrum, thus being suitable for their use in micromachining processes, in particular the micromachining of glass and silicon. Furthermore, the wavelengths of 1030 nanometers and 1064 nanometers correspond to excitation lines of neodymium and ytterbium, particularly useful for micromachining using laser pulses of these wavelengths.
[0039] Avantageusement, les impulsions lasers dont la longueur d’onde est dans le spectre visible, dans le proche infrarouge ou le moyen infrarouge sont particulièrement avantageuses pour le micro-usinage du plastique. [0040] Dans un mode de réalisation de l’invention, alternatif ou cumulatif, l’oscillateur laser est agencé de sorte que l’impulsion laser émise par ledit oscillateur présente une longueur d’onde dans le spectre visible. Advantageously, laser pulses whose wavelength is in the visible spectrum, in the near infrared or the mid infrared are particularly advantageous for the micromachining of plastic. [0040] In an alternative or cumulative embodiment of the invention, the laser oscillator is arranged so that the laser pulse emitted by said oscillator has a wavelength in the visible spectrum.
[0041] Avantageusement, les impulsions lasers dont la longueur d’onde est dans le spectre visible sont particulièrement avantageuses pour le micro-usinage du plastique. [0041] Advantageously, laser pulses whose wavelength is in the visible spectrum are particularly advantageous for the micromachining of plastic.
[0042] Avantageusement encore, les impulsions laser de longueur d’onde de 1030 nanomètres et celles de 1064 nanomètres possèdent la propriété d’être faiblement atténuées dans les fibres optiques ce qui rend ces longueurs d’onde particulièrement intéressantes pour préserver la puissance le long du parcours de l’impulsion au sein du dispositif, notamment le long des canaux de propagation. Avantageusement encore, les longueurs d’onde de 1030 nanomètres et 1064 nanomètres sont particulièrement souhaitables pour le micro-usinage, notamment la découpe et la modification de matériaux tels que le verre, le métal, et le plastique. [0042] Advantageously again, the laser pulses of wavelength 1030 nanometers and those of 1064 nanometers have the property of being slightly attenuated in the optical fibers which makes these wavelengths particularly interesting for preserving the power along of the path of the pulse within the device, in particular along the propagation channels. Advantageously, the wavelengths of 1030 nanometers and 1064 nanometers are particularly desirable for micromachining, including cutting and modifying materials such as glass, metal, and plastic.
[0043] Dans un mode de réalisation de l’invention, alternatif ou cumulatif, le dispositif lumineux comporte un contrôleur de l’oscillateur laser, agencé pour générer un signal de contrôle dudit oscillateur laser, ledit signal de contrôle étant une instruction de génération de ladite impulsion initiale. [0043] In an alternative or cumulative embodiment of the invention, the light device comprises a controller of the laser oscillator, arranged to generate a control signal of said laser oscillator, said control signal being an instruction for generating said initial impulse.
[0044] Avantageusement, le contrôleur de l’oscillateur permet de gouverner la génération des impulsions, notamment la cadence de génération des impulsions et leur intensité, et permet d’assurer le maintien de la stabilité et de la précision de la fréquence des impulsions. [0044] Advantageously, the controller of the oscillator makes it possible to govern the generation of the pulses, in particular the rate of generation of the pulses and their intensity, and makes it possible to ensure the maintenance of the stability and precision of the frequency of the pulses.
[0045] Dans un mode de réalisation alternatif de l’invention, le contrôleur est agencé pour générer un signal de contrôle définissant un profil temporel de l’impulsion initiale tel que la composition additive, effectuée par le composant de regroupement, des impulsions secondaires décalées et modulées soit dépourvue de bruit d’interférence. [0045] In an alternative embodiment of the invention, the controller is arranged to generate a control signal defining a temporal profile of the initial pulse such that the additive composition, carried out by the grouping component, of the shifted secondary pulses and modulated is free from interference noise.
[0046] Avantageusement, la suppression du bruit d’interférence permet d’améliorer le profil et la stabilité de l’impulsion terminale. [0046] Advantageously, the suppression of the interference noise makes it possible to improve the profile and the stability of the terminal pulse.
[0047] Dans un mode de réalisation de l’invention, alternatif ou cumulatif, l’oscillateur laser est agencé pour générer un signal de contrôle comportant une première composante continue, notamment constante, et une deuxième composante périodique et discontinue. [0047] In an alternative or cumulative embodiment of the invention, the laser oscillator is arranged to generate a control signal comprising a first continuous component, in particular constant, and a second periodic and discontinuous component.
[0048] Avantageusement, la combinaison des composantes continue et périodique discontinue permet de séparer des effets à long et à court terme permettant d’optimiser les paramètres de fonctionnement de l’oscillateur laser et les performances de ce dernier, notamment en ajustant la fréquence et l’amplitude de la composante périodique. [0048] Advantageously, the combination of the continuous and periodic discontinuous components makes it possible to separate long and short term effects making it possible to optimize the operating parameters of the laser oscillator and the performances of the latter, in particular by adjusting the frequency and the amplitude of the periodic component.
[0049] Avantageusement encore, la combinaison des composantes continue et périodique discontinue permet de synchroniser l’oscillateur laser avec d’autres systèmes en utilisant la composante périodique comme référence de synchronisation. [0050] Dans un mode de réalisation de l’invention, alternatif ou cumulatif, les canaux de propagation et les composants de séparation et de regroupement sont agencés de sorte que les profils des impulsions décalées et modulées se recouvrent d’au moins 10 % de leur largeur à mi-hauteur. [0049] Advantageously, the combination of the continuous and discontinuous periodic components makes it possible to synchronize the laser oscillator with other systems using the periodic component as a synchronization reference. [0050] In an alternative or cumulative embodiment of the invention, the propagation channels and the separation and grouping components are arranged so that the profiles of the shifted and modulated pulses overlap by at least 10% of their width at half height.
[0051] Il est connu que lorsque deux impulsions laser se recouvrent, leur superposition peut produire des interférences qui peuvent affecter la qualité de l’impulsion résultante. Avantageusement, en ayant des impulsions laser qui se recouvrent d’au moins 10% de leur largeur à mi-hauteur, on assure que leur superposition est suffisamment faible pour minimiser ces effets indésirables. [0051] It is known that when two laser pulses overlap, their superposition can produce interference which can affect the quality of the resulting pulse. Advantageously, by having laser pulses which overlap by at least 10% of their width at half height, we ensure that their superposition is sufficiently low to minimize these undesirable effects.
[0052] Dans un mode de réalisation de l’invention, alternatif ou cumulatif, l’oscillateur laser est agencé de sorte que l’impulsion initiale comporte une dérive de fréquence pendant la durée de cette impulsion. Le cas échéant, le dispositif peut comprendre au moins un composant optique agencé pour modifier la dérive de fréquence d’une impulsion secondaire se propageant dans l’un des canaux de propagation. [0052] In an alternative or cumulative embodiment of the invention, the laser oscillator is arranged so that the initial pulse includes a frequency drift during the duration of this pulse. Where applicable, the device may comprise at least one optical component arranged to modify the frequency drift of a secondary pulse propagating in one of the propagation channels.
[0053] Avantageusement, la modification de la dérive de fréquence d’une impulsion secondaire offre un moyen supplémentaire de modulation de l’impulsion terminale, résultant du regroupement de l’ensemble des impulsions secondaires décalées et modulées. [0053] Advantageously, modifying the frequency drift of a secondary pulse offers an additional means of modulating the terminal pulse, resulting from the grouping of all the shifted and modulated secondary pulses.
[0054] Avantageusement, la modification de la dérive de fréquence d’une impulsion secondaire pourra notamment être obtenue en employant des réseaux de diffraction, des prismes, des fibres dispersives ou de réseaux de Bragg à pas variable. [0054] Advantageously, the modification of the frequency drift of a secondary pulse could in particular be obtained by using diffraction gratings, prisms, dispersive fibers or Bragg gratings with variable pitch.
[0055] Dans un mode de réalisation de l’invention, alternatif ou cumulatif, chaque canal de transmission comporte au moins une fibre optique. [0055] In an alternative or cumulative embodiment of the invention, each transmission channel comprises at least one optical fiber.
[0056] Avantageusement, les fibres optiques engendrent une très faible perte de puissance et une faible dégradation de l’impulsion laser qui s’y propage, ce qui permet de transmettre efficacement lesdites impulsions laser sur des longues distances. Ainsi, dans le cas où le décalage des impulsions est obtenu en utilisant des canaux de longueur différente, le recours à des canaux de propagations réalisés en fibres optiques permet de préserver la qualité et la puissance des impulsions secondaires jusqu’au moment où ces dernières seront regroupées par le composant de regroupement. [0056] Advantageously, the optical fibers generate a very low power loss and a low degradation of the laser pulse which propagates there, which makes it possible to effectively transmit said laser pulses over long distances. Thus, in the case where the offset of the pulses is obtained by using channels of different length, the use of propagation channels made of optical fibers makes it possible to preserve the quality and power of the secondary pulses until the moment when the latter will be grouped by the grouping component.
[0057] Avantageusement encore, l’utilisation des fibres optiques permet de tirer parti de leur finesse et légèreté ainsi que de leur flexibilité permettant d’obtenir des canaux de propagation de formes variées. [0057] Advantageously again, the use of optical fibers makes it possible to take advantage of their thinness and lightness as well as their flexibility making it possible to obtain propagation channels of various shapes.
[0058] Dans un mode de réalisation de l’invention, alternatif ou cumulatif, le composant de modulation est agencé pour ajuster la puissance d’au moins l’une desdites impulsions secondaires selon un gain ou une perte de puissance choisi de sorte que l’impulsion terminale présente un profil prédéterminé. [0058] In an alternative or cumulative embodiment of the invention, the modulation component is arranged to adjust the power of at least one of said secondary pulses according to a gain or loss of power chosen so that the The terminal pulse has a predetermined profile.
[0059] En procédant ainsi, l'invention vise à utiliser la modulation en puissance des im- pulsions secondaires qui se propagent dans les canaux de propagation pour contrôler la forme du profil temporel de l'impulsion terminale obtenue lors de la composition additive de ces impulsions secondaires. On comprend, alors que l’invention propose de contrôler précisément les caractéristiques temporelles de l'impulsion terminale en modulant la puissance des impulsions secondaires qui se propagent dans les différents canaux de propagation, cela est obtenu en modulant chaque impulsion secondaire selon une pondération établie par le composant de modulation. [0059] By proceeding in this way, the invention aims to use the power modulation of the im- secondary pulses which propagate in the propagation channels to control the shape of the time profile of the terminal pulse obtained during the additive composition of these secondary pulses. It will be understood that while the invention proposes to precisely control the temporal characteristics of the terminal pulse by modulating the power of the secondary pulses which propagate in the different propagation channels, this is obtained by modulating each secondary pulse according to a weighting established by the modulation component.
[0060] Dans un mode de réalisation de l’invention, alternatif ou cumulatif, le composant de modulation et le composant de séparation forment un même élément optique agencé pour séparer l’impulsion initiale en deux ou plusieurs impulsions secondaires présentant chacune une puissance distincte prédéterminée et agencé pour transmettre chacune desdites impulsions secondaires vers un canal de propagation dédié. [0060] In an alternative or cumulative embodiment of the invention, the modulation component and the separation component form the same optical element arranged to separate the initial pulse into two or more secondary pulses each having a predetermined distinct power and arranged to transmit each of said secondary pulses to a dedicated propagation channel.
[0061] Avantageusement, ce mode de réalisation permet de réduire l’encombrement du dispositif en combinant les composant de séparation et modulation précédemment évoquées en un seul et même composant. [0061] Advantageously, this embodiment makes it possible to reduce the bulk of the device by combining the separation and modulation components previously mentioned in a single component.
[0062] Dans un mode de réalisation de l’invention, alternatif ou cumulatif, au moins l’un des canaux de propagation comporte un composant de modulation en puissance propre à ajuster la puissance de l’impulsion secondaire qui s’y propage. [0062] In an alternative or cumulative embodiment of the invention, at least one of the propagation channels comprises a power modulation component capable of adjusting the power of the secondary pulse which propagates there.
[0063] Avantageusement, le fait d’introduire le composant de modulation au sein d’un des canaux de propagation permet de réaliser la modulation sur une localisation quelconque du canal, notamment en début de canal, en milieu de canal ou en fin de canal. [0063] Advantageously, the fact of introducing the modulation component within one of the propagation channels makes it possible to carry out the modulation on any location of the channel, in particular at the start of the channel, in the middle of the channel or at the end of the channel. .
[0064] Avantageusement, le composant de modulation de puissance pourra notamment être agencé pour augmenter ou diminuer la puissance de l’impulsion secondaire sur laquelle il agit. [0064] Advantageously, the power modulation component could in particular be arranged to increase or decrease the power of the secondary pulse on which it acts.
[0065] Avantageusement encore, le canal de propagation comporte plusieurs composants de modulation le long du canal de propagation. [0065] Advantageously, the propagation channel comprises several modulation components along the propagation channel.
[0066] Avantageusement encore, le composant de modulation de puissance pourra notamment être un composant optique passif comme un miroir partiellement réfléchissant, un tronçon de fibre optique soumis à une perturbation mécanique, un réseau de Bragg partiellement réfléchissant, un assemblage optique passif comme un ensemble « lame d’onde L/2 + polariseur » ou un composant actif comme un modulateur à cristaux liquide, un modulateur électro-optique, un modulateur acousto- optique ou encore un modulateur à semi-conducteurs. [0066] Advantageously, the power modulation component could in particular be a passive optical component such as a partially reflective mirror, a section of optical fiber subjected to a mechanical disturbance, a partially reflective Bragg grating, a passive optical assembly such as an assembly “L/2 waveplate + polarizer” or an active component such as a liquid crystal modulator, an electro-optical modulator, an acousto-optical modulator or even a semiconductor modulator.
[0067] Dans un mode de réalisation de l’invention, alternatif ou cumulatif, au moins l’un des canaux de propagation comporte un filtre d’intensité de l’impulsion secondaire qui s’y propage. [0067] In an alternative or cumulative embodiment of the invention, at least one of the propagation channels comprises an intensity filter of the secondary pulse which propagates there.
[0068] Avantageusement encore, le filtre d’intensité pourra être un absorbant saturable, permettant un filtrage progressif de l’impulsion secondaire et notamment apte à filtrer les intensités basses des impulsions et laissant passer les intensités hautes. [0068] Advantageously again, the intensity filter could be a saturable absorber, allowing progressive filtering of the secondary pulse and in particular capable of filtering the low intensities of the pulses and allowing the high intensities to pass.
[0069] Avantageusement, les filtres d’intensité pourront notamment être fabriqués en verre, en céramique ou encore en nanomatériaux en couches minces ou sous forme de nanoparticules à ase de semiconducteurs, dopés ou non, ou encore des logement remplis de substances chimiques, notamment de gaz. [0069] Advantageously, the intensity filters could in particular be made of glass, ceramic or even nanomaterials in thin layers or in the form of nanoparticles based on semiconductors, doped or not, or even housings filled with chemical substances, in particular gas.
[0070] Dans un mode de réalisation de l’invention, alternatif ou cumulatif, au moins l’un des canaux de propagation comporte un filtre spectral. [0070] In an alternative or cumulative embodiment of the invention, at least one of the propagation channels comprises a spectral filter.
[0071] Avantageusement, un canal de propagation comportant un filtre spectral permet de sélectionner une plage de longueurs d’onde précise de l’impulsion secondaire qui s’y propage, notamment adaptée pour contrôler finement le spectre de l’impulsion finale résultant du regroupement des impulsions secondaires décalées et modulées. [0071] Advantageously, a propagation channel comprising a spectral filter makes it possible to select a precise range of wavelengths of the secondary pulse which propagates there, in particular adapted to finely control the spectrum of the final pulse resulting from the grouping shifted and modulated secondary pulses.
[0072] Dans un mode de réalisation de l’invention, alternatif ou cumulatif, le composant de séparation, les canaux de propagation, le composant de modulation et le composant de regroupement forment un premier étage optique du dispositif, de sorte qu’un deuxième étage optique comporte : un composant de séparation, des canaux de propagation, un composant de modulation et un composant de regroupement , le deuxième étage optique étant connecté en série avec le premier étage optique de sorte que le composant de séparation du deuxième étage optique reçoive l’impulsion terminale composée par le composant de regroupement du premier étage optique. [0072] In an alternative or cumulative embodiment of the invention, the separation component, the propagation channels, the modulation component and the grouping component form a first optical stage of the device, so that a second optical stage comprises: a separation component, propagation channels, a modulation component and a grouping component, the second optical stage being connected in series with the first optical stage so that the separation component of the second optical stage receives the The terminal pulse composed by the grouping component of the first optical stage.
[0073] Avantageusement, la première impulsion terminale obtenue par le premier composant de regroupement peut être séparée par le deuxième composant de séparation en plusieurs impulsions secondaires qui seront modulées par le deuxième composant de modulation avant d’être regroupées par le deuxième composant de regroupement du deuxième étage optique pour génère ainsi une deuxième impulsion terminale. Advantageously, the first terminal pulse obtained by the first grouping component can be separated by the second separation component into several secondary pulses which will be modulated by the second modulation component before being grouped by the second grouping component of the second optical stage to thus generate a second terminal pulse.
[0074] Avantageusement encore, l’invention peut comporter un nombre N d’étages optiques connectés en réseau et de sorte qu’une impulsion terminale d’un étage donné serve comme impulsion initiale d’un autre étage. Les N étages pourront être disposés selon une configuration de réseau quelconque, comportant tout ou partie du réseau en connexion en série et/ou en parallèle. [0074] Advantageously again, the invention can include a number N of optical stages connected in a network and such that a terminal pulse of a given stage serves as an initial pulse of another stage. The N stages could be arranged according to any network configuration, comprising all or part of the network in series and/or parallel connection.
[0075] Dans un mode de réalisation de l’invention, alternatif ou cumulatif, le dispositif permet de moduler en phase et/ou en amplitude les impulsions secondaires au travers d’au moins un élément perturbateur des canaux de propagation, notamment dans le cas des canaux de propagation réalisés en fibres optiques. Cela peut être réalisé en utilisant un élément perturbant qui agit localement sur la température, notamment un dispositif à effet Peltier, et/ou qui modifie localement la fibre optique mécaniquement, notamment un moyen de pression. Cette capacité à moduler les impulsions secondaires permet une flexibilité accrue dans les applications où ces impulsions sont utilisées. [0075] In an alternative or cumulative embodiment of the invention, the device makes it possible to modulate in phase and/or in amplitude the secondary pulses through at least one disturbing element of the propagation channels, particularly in the case propagation channels made from optical fibers. This can be achieved by using a disturbing element which acts locally on the temperature, in particular a Peltier effect device, and/or which locally modifies the optical fiber mechanically, in particular a pressure means. This ability to modulate secondary impulses allows for increased flexibility in applications where these pulses are used.
[0076] Dans un mode de réalisation de l’invention, alternatif ou cumulatif, le dispositif comporte une enceinte isolante apte à isoler thermiquement et/ou mécaniquement un ou plusieurs éléments parmi : le composant de séparation, les canaux de propagation, le composant de modulation et le composant de regroupement. [0076] In an alternative or cumulative embodiment of the invention, the device comprises an insulating enclosure capable of thermally and/or mechanically insulating one or more elements among: the separation component, the propagation channels, the modulation and the grouping component.
[0077] La propagation des impulsions secondaires dans différents canaux de propagation se fait avec des variations de phase légèrement différentes, ces variations peuvent être amplifiées par des perturbations, notamment thermiques, ce qui peut causer des interférences et des modifications importantes de l'impulsion terminale. [0077] The propagation of the secondary pulses in different propagation channels takes place with slightly different phase variations; these variations can be amplified by disturbances, in particular thermal disturbances, which can cause interference and significant modifications of the terminal pulse. .
[0078] Avantageusement, l’enceinte isolante permet de réduire les effets de bruitage de l’impulsion terminale dus aux perturbations mécaniques, notamment sismiques, et/ou thermiques externes, notamment radiatives et/ou convectives. Par ailleurs, l’isolation thermique permet d’améliorer la qualité de l’impulsion terminale en évitant d’amplifier des effets d’interférence intrinsèques au dispositif. [0078] Advantageously, the insulating enclosure makes it possible to reduce the noise effects of the terminal pulse due to mechanical disturbances, in particular seismic, and/or external thermal, in particular radiative and/or convective. Furthermore, thermal insulation makes it possible to improve the quality of the terminal pulse by avoiding amplifying interference effects intrinsic to the device.
[0079] Avantageusement encore, l’enceinte isolante pourra notamment être réalisée en matériaux résistants à la chaleur, notamment des feuilles ou des plaques en aluminium et/ou en cuivre, des céramiques telles que l’alumine et le carbure de silicium ou encore des matériaux composites, notamment à base des fibres de carbone. Avantageusement encore, l’enceinte isolante pourra notamment être réalisée en matériaux résistants à la pression et pourra être conçue pour minimiser les vibrations et les chocs extérieurs, notamment en caoutchouc et/ou en mousse, par exemple, sous forme de coussinets ou de patins. [0079] Advantageously, the insulating enclosure could in particular be made of heat-resistant materials, in particular aluminum and/or copper sheets or plates, ceramics such as alumina and silicon carbide or even ceramics. composite materials, particularly based on carbon fibers. Advantageously, the insulating enclosure may in particular be made of pressure-resistant materials and may be designed to minimize vibrations and external shocks, in particular in rubber and/or foam, for example, in the form of pads or pads.
[0080] L’invention a également pour objet un système optique, comportant un dispositif selon l’invention et au moins un amplificateur optique et/ou un système de conversion non-linéaire, apte à recevoir l’impulsion terminale composée par le dispositif. [0080] The invention also relates to an optical system, comprising a device according to the invention and at least one optical amplifier and/or a non-linear conversion system, capable of receiving the terminal pulse composed by the device.
[0081] Avantageusement, le système de conversion non-linéaire permet de modifier la longueur d’onde de l’impulsion terminale, y compris dans le cas où l’impulsion a été amplifiée. Ledit système de conversion non-linéaire permettant de modifier la longueur d’onde de l’impulsion terminale pourra notamment réaliser un doublage de fréquence. [0081] Advantageously, the non-linear conversion system makes it possible to modify the wavelength of the terminal pulse, including in the case where the pulse has been amplified. Said non-linear conversion system making it possible to modify the wavelength of the terminal pulse can in particular carry out frequency doubling.
[0082] La description qui précède explique clairement comment l'invention permet d'atteindre les objectifs qu'elle s'est fixée, à savoir produire une impulsion laser de longueur comprise entre 100 picosecondes et 500 picosecondes avec un contrôle sur le profil des impulsions et sans limitation du spectre. [0082] The preceding description clearly explains how the invention makes it possible to achieve the objectives it has set for itself, namely to produce a laser pulse of length between 100 picoseconds and 500 picoseconds with control over the profile of the pulses. and without spectrum limitation.
Brève description des figures. Brief description of the figures.
[0083] D’autres avantages et caractéristiques de la présente invention sont maintenant décrits à l’aide d’exemples uniquement illustratifs et nullement limitatifs de la portée de l’invention, et à partir des dessins annexés, dessins sur lesquels les différentes figures représentent : [0084] [Fig.1] représente, schématiquement et partiellement, un dispositif lumineux délivrant une impulsion laser selon un mode de réalisation de l’invention. [0083] Other advantages and characteristics of the present invention are now described using examples that are purely illustrative and in no way limiting the scope of the invention, and from the appended drawings, drawings in which the different figures represent : [0084] [Fig.1] represents, schematically and partially, a light device delivering a laser pulse according to one embodiment of the invention.
[0085] [Fig.2] représente, schématiquement et partiellement, un graphique temporel décrivant le profil type de l’impulsion laser initiale, selon un mode de réalisation de l’invention. [0085] [Fig.2] represents, schematically and partially, a time graph describing the typical profile of the initial laser pulse, according to one embodiment of the invention.
[0086] [Fig.3] représente, schématiquement et partiellement, un graphique temporel décrivant le profil type de l’impulsion laser terminale, selon un mode de réalisation de l’invention. [0086] [Fig.3] represents, schematically and partially, a time graph describing the typical profile of the terminal laser pulse, according to one embodiment of the invention.
[0087] [Fig.4] représente, schématiquement et partiellement, un dispositif lumineux émettant une impulsion laser et comportant deux étages optiques selon un mode de réalisation de l’invention. [0087] [Fig.4] represents, schematically and partially, a light device emitting a laser pulse and comprising two optical stages according to one embodiment of the invention.
[0088] Dans la description qui suit, les éléments identiques, par structure ou par fonction, apparaissant sur différentes figures conservent, sauf précision contraire, les mêmes références. [0088] In the description which follows, identical elements, by structure or by function, appearing in different figures retain, unless otherwise specified, the same references.
Description des modes de réalisation. Description of the embodiments.
[0089] On a représenté en [Fig.l], selon un mode de réalisation de l’invention, un dispositif lumineux 6 émettant une impulsion laser comportant : [0089] We show in [Fig.l], according to one embodiment of the invention, a light device 6 emitting a laser pulse comprising:
[0090] un oscillateur laser 1 émettant une impulsion initiale ; [0090] a laser oscillator 1 emitting an initial pulse;
[0091] un composant de séparation 2 de l’impulsion initiale en quatre impulsions secondaires ; chacune desdites impulsions secondaires est transmise vers un canal de propagation dédié 41, 42, 43, 44 ; chacun desdits canaux de propagation est agencé pour décaler temporellement l’impulsion secondaire qui s’y propage pendant une quantité de temps donnée ; [0091] a separation component 2 of the initial pulse into four secondary pulses; each of said secondary pulses is transmitted to a dedicated propagation channel 41, 42, 43, 44; each of said propagation channels is arranged to temporally shift the secondary pulse which propagates there for a given quantity of time;
[0092] quatre composants de modulation de puissance 31, 32, 33, 34 agencés pour ajuster la puissance des impulsions secondaires selon une consigne prédéterminée ; [0092] four power modulation components 31, 32, 33, 34 arranged to adjust the power of the secondary pulses according to a predetermined setpoint;
[0093] un composant de regroupement 5 agencé pour composer additivement lesdites impulsions secondaires décalées et modulées en une seule et même impulsion terminale ; ladite impulsion terminale étant une impulsion laser de durée supérieure à la durée de l’impulsion initiale. [0093] a grouping component 5 arranged to additively compose said offset and modulated secondary pulses into a single terminal pulse; said terminal pulse being a laser pulse of duration greater than the duration of the initial pulse.
[0094] Cet exemple est donné à titre non limitatif ; on pourra concevoir d’autres configurations géométriques sans sortir du cadre de la présente invention. On pourra notamment faire varier le nombre de canaux de propagation ainsi que le nombre de composants de modulation de puissance, leur agencement au regard du composant de séparation et/ou du composant de regroupement. [0094] This example is given on a non-limiting basis; other geometric configurations could be designed without departing from the scope of the present invention. In particular, it will be possible to vary the number of propagation channels as well as the number of power modulation components, their arrangement with regard to the separation component and/or the grouping component.
[0095] Dans l’exemple décrit, l’oscillateur laser 1 comporte une diode laser à rétroaction répartie. [0095] In the example described, the laser oscillator 1 comprises a laser diode with distributed feedback.
[0096] Sans restriction de la portée de l’invention, l’oscillateur laser 1 pourra comporter alternativement une source d’impulsions laser à verrouillage de mode. [0097] L’oscillateur laser 1 est agencé de sorte à émettre une impulsion laser d’une longueur d’onde sensiblement égale à 1030 nm. Alternativement, la longueur d’onde d’émission pourra être sensiblement égale à 1064 nm. [0096] Without restricting the scope of the invention, the laser oscillator 1 may alternatively include a source of mode-locked laser pulses. The laser oscillator 1 is arranged so as to emit a laser pulse with a wavelength substantially equal to 1030 nm. Alternatively, the emission wavelength could be substantially equal to 1064 nm.
[0098] Le dispositif lumineux 6 comporte un contrôleur de l’oscillateur laser 1 (non représenté) agencé pour générer un signal de contrôle dudit oscillateur laser 1, ledit signal de contrôle étant une instruction de génération de l’impulsion initiale. The light device 6 comprises a controller of the laser oscillator 1 (not shown) arranged to generate a control signal of said laser oscillator 1, said control signal being an instruction for generating the initial pulse.
[0099] Le contrôleur de l’oscillateur laser (non représenté) est agencé pour générer un signal de contrôle définissant un profil de l’impulsion initiale tel que la composition additive, par le composant de regroupement 5, des impulsions secondaires décalées et modulées soit dépourvue de bruit d’interférence. [0099] The controller of the laser oscillator (not shown) is arranged to generate a control signal defining a profile of the initial pulse such that the additive composition, by the grouping component 5, of the shifted and modulated secondary pulses is free from interference noise.
[0100] Le contrôleur de l’oscillateur laser (non représenté) est également agencé pour générer un signal de contrôle comportant une première composante continue, notamment constante, et une deuxième composante périodique et discontinue. [0100] The controller of the laser oscillator (not shown) is also arranged to generate a control signal comprising a first continuous component, in particular constant, and a second periodic and discontinuous component.
[0101] Les canaux de propagation 41, 42, 43, 44 et les composants de séparation 2 et de regroupement 5 sont agencés de sorte que les profils des impulsions décalées et modulées se recouvrent d’au moins 10 % de leur largeur à mi-hauteur. [0101] The propagation channels 41, 42, 43, 44 and the separation components 2 and grouping components 5 are arranged so that the profiles of the shifted and modulated pulses overlap by at least 10% of their width at midpoint. height.
[0102] L’oscillateur laser 1 est agencé de sorte que l’impulsion initiale comporte une dérive de fréquence pendant la durée de cette impulsion. [0102] The laser oscillator 1 is arranged so that the initial pulse includes a frequency drift during the duration of this pulse.
[0103] Le dispositif 6 comprend au moins un composant optique (non représenté) agencé pour modifier la dérive de fréquence d’une impulsion secondaire se propageant dans l’un des canaux de propagation 41, 42, 43, 44. [0103] The device 6 comprises at least one optical component (not shown) arranged to modify the frequency drift of a secondary pulse propagating in one of the propagation channels 41, 42, 43, 44.
[0104] Chaque canal de transmission 41, 42, 43, 44 comporte au moins une fibre optique. [0104] Each transmission channel 41, 42, 43, 44 comprises at least one optical fiber.
[0105] Les composants de modulation 31, 32, 33, 34 sont agencés pour ajuster la puissance d’au moins l’une des impulsions secondaires selon un gain ou une perte de puissance choisi de sorte que l’impulsion terminale présente un profil prédéterminé. [0105] The modulation components 31, 32, 33, 34 are arranged to adjust the power of at least one of the secondary pulses according to a power gain or loss chosen so that the terminal pulse has a predetermined profile .
[0106] Les canaux de propagation 41, 42, 43, 44 comportent un filtre d’intensité (non représentée) de l’impulsion secondaire qui s’y propage. [0106] The propagation channels 41, 42, 43, 44 include an intensity filter (not shown) of the secondary pulse which propagates there.
[0107] Les canaux de propagation 41, 42, 43, 44 comportent un filtre spectral (non représenté) de l’impulsion secondaire qui s’y propage. [0107] The propagation channels 41, 42, 43, 44 include a spectral filter (not shown) of the secondary pulse which propagates there.
[0108] Le dispositif comporte une enceinte isolante (non représenté) apte à isoler thermiquement et/ou mécaniquement les composants de séparation 2, de modulation 31, 32, 33, 34 et de regroupement 5. [0108] The device comprises an insulating enclosure (not shown) capable of thermally and/or mechanically insulating the separation 2, modulation 31, 32, 33, 34 and grouping 5 components.
[0109] On a représenté en [Fig.2] le graphique temporel décrivant le profil type de l’impulsion laser initiale, selon un mode de réalisation de l’invention. Le profil de l’impulsion peut notamment prendre la forme d’une distribution gaussienne, d’une sécante hyperbolique, ou plus généralement d’une distribution de Gumbel ou de Weibull. [0109] The time graph describing the typical profile of the initial laser pulse is shown in [Fig.2], according to one embodiment of the invention. The pulse profile can notably take the form of a Gaussian distribution, a hyperbolic secant, or more generally a Gumbel or Weibull distribution.
[0110] Le profil de l’impulsion initiale possède une durée à mi-hauteur d’ approximativement de 50 picosecondes et présente un front montant de pente sensiblement plus faible à celle du front descendant. [0110] The profile of the initial pulse has a duration at half height of approximately 50 picoseconds and has a rising edge with a slope significantly lower than that of the falling edge.
[0111] Ce profil type correspond au profil d’une impulsion laser émise par l’oscillateur laser 1 et présente une longueur d’onde sensiblement de 1030 nanomètres selon un mode de réalisation de l’invention ou de 1064 nanomètres selon un autre mode de réalisation. [0111] This typical profile corresponds to the profile of a laser pulse emitted by the laser oscillator 1 and has a wavelength substantially of 1030 nanometers according to one embodiment of the invention or of 1064 nanometers according to another mode of realization.
[0112] On a représenté en [Fig.3] le graphique temporel décrivant le profil type de l’impulsion laser terminale, selon un mode de réalisation de l’invention. [0112] The time graph describing the typical profile of the terminal laser pulse is shown in [Fig.3], according to one embodiment of the invention.
[0113] Le profil de l’impulsion terminale de la [Fig.3] est obtenu après regroupement, par le composant de regroupement 5, 501, 502, des impulsions secondaires décalées et modulées par le composant de séparation 2, 201, 202 et le composant de modulation 31, 32, 33, 34, 301, 302, 303, 304. Il est notable que le profil de l’impulsion terminale de la [Fig.3] ne comporte pas de bruit d’interférence et est de forme sensiblement similaire à une impulsion carrée de 180 picosecondes de durée, durée notamment supérieure à la durée de l’impulsion initiale représentée en [Fig.2]. [0113] The profile of the terminal pulse in [Fig.3] is obtained after grouping, by the grouping component 5, 501, 502, the secondary pulses shifted and modulated by the separation component 2, 201, 202 and the modulation component 31, 32, 33, 34, 301, 302, 303, 304. It is notable that the profile of the terminal pulse in [Fig.3] does not include interference noise and is of the form substantially similar to a square pulse of 180 picoseconds duration, duration notably greater than the duration of the initial pulse represented in [Fig.2].
[0114] Le profil de l’impulsion terminale de la [Fig.3] résultant de la composition additive par le composant de regroupement 5, 501, 502 des impulsions secondaires décalées et modulées est dépourvue de bruit d’interférence du fait que, d’une part, le contrôleur de l’oscillateur laser (non représenté) est agencé à cet effet, et d’autre part l’impulsion initiale présente une dérive de fréquence qui limite la cohérence des impulsions secondaires décalées dans le temps. [0114] The profile of the terminal pulse of [Fig.3] resulting from the additive composition by the grouping component 5, 501, 502 of the shifted and modulated secondary pulses is devoid of interference noise due to the fact that, d On the one hand, the controller of the laser oscillator (not shown) is arranged for this purpose, and on the other hand the initial pulse has a frequency drift which limits the coherence of the secondary pulses shifted in time.
[0115] On a représenté en [Fig.4], un dispositif lumineux émettant une impulsion laser et comportant deux étages optiques selon un mode de réalisation de l’invention. [0115] We show in [Fig.4], a light device emitting a laser pulse and comprising two optical stages according to one embodiment of the invention.
[0116] Le composant de séparation 201, les canaux de propagation (non représentés), les composants de modulation 301, 302 et le composant de regroupement 501 forment un premier étage optique du dispositif, de sorte qu’un deuxième étage optique comporte un composant de séparation 202, des canaux de propagation (non représentés), deux composants de modulation 303, 304 et un composant de regroupement 502, le deuxième étage optique étant connecté en série avec le premier étage optique de sorte que le composant de séparation 202 du deuxième étage optique reçoive l’impulsion terminale composée par le composant de regroupement 501 du premier étage optique. [0116] The separation component 201, the propagation channels (not shown), the modulation components 301, 302 and the grouping component 501 form a first optical stage of the device, so that a second optical stage comprises a component separation 202, propagation channels (not shown), two modulation components 303, 304 and a grouping component 502, the second optical stage being connected in series with the first optical stage so that the separation component 202 of the second optical stage receives the terminal pulse composed by the grouping component 501 of the first optical stage.
[0117] Le dispositif lumineux de la [Fig.4] comporte également un récepteur 600 de l’impulsion terminale. [0117] The light device in [Fig.4] also includes a receiver 600 of the terminal pulse.
[0118] Les caractéristiques optionnelles du dispositif de la [Fig.l] précédemment décrites sont également applicables au dispositif de la [Fig.4]. [0118] The optional characteristics of the device of [Fig.l] previously described are also applicable to the device of [Fig.4].
[0119] Le dispositif comporte une enceinte isolante (non représentée) apte à isoler thermiquement et/ou mécaniquement les composants de séparation 201, 202, de modulation 301, 302, 303, 304 et de regroupement 501, 502. [0119] The device comprises an insulating enclosure (not shown) capable of thermally and/or mechanically insulating the separation components 201, 202, modulation 301, 302, 303, 304 and grouping 501, 502.
[0120] En tout état de cause, l'invention ne saurait se limiter aux modes de réalisation spéci- fiquement décrits dans ce document, et s'étend en particulier à tous moyens équivalents et à toute combinaison techniquement opérante de ces moyens. On pourra en particulier envisager d’autres dispositions géométriques des composants du dispositif, ainsi que d’autres sources d’émission laser et d’autres matériaux pour réaliser les canaux de propagation. [0120] In any case, the invention cannot be limited to the specific embodiments fically described in this document, and extends in particular to all equivalent means and to any technically effective combination of these means. In particular, it will be possible to consider other geometric arrangements of the components of the device, as well as other sources of laser emission and other materials to produce the propagation channels.

Claims

Revendications Claims
[Revendication 1] Dispositif lumineux (6) émettant une impulsion laser comportant : a. un oscillateur laser (1) émettant une impulsion laser, dite impulsion initiale ; b. un composant de séparation (2) de ladite impulsion initiale en deux ou plusieurs impulsions secondaires, ledit composant de séparation (2) étant agencé pour transmettre chacune desdites impulsions secondaires vers un canal de propagation (41, 42, 43, 44) dédié, chaque canal de propagation (41, 42, 43, 44) étant agencé pour décaler temporellement l’impulsion secondaire qui s’y propage d’une quantité de temps donnée, notamment distincte de celles des autres canaux de propagation (41, 42, 43, 44) ; c. un composant de modulation de puissance (31, 32 33, 34, 301, 302, 303, 304) agencé pour ajuster la puissance d’au moins l’une desdites impulsions secondaires selon une consigne prédéterminée ; d. un composant de regroupement d’impulsions (5) agencé pour composer additivement lesdites impulsions secondaires décalées et modulées en une seule et même impulsion, dite impulsion terminale ; ladite impulsion terminale étant une impulsion laser de durée supérieure à la durée de l’impulsion initiale. [Claim 1] Light device (6) emitting a laser pulse comprising: a. a laser oscillator (1) emitting a laser pulse, called the initial pulse; b. a separation component (2) of said initial pulse into two or more secondary pulses, said separation component (2) being arranged to transmit each of said secondary pulses to a dedicated propagation channel (41, 42, 43, 44), each propagation channel (41, 42, 43, 44) being arranged to temporally shift the secondary pulse which propagates there by a given quantity of time, in particular distinct from those of the other propagation channels (41, 42, 43, 44); vs. a power modulation component (31, 32 33, 34, 301, 302, 303, 304) arranged to adjust the power of at least one of said secondary pulses according to a predetermined setpoint; d. a pulse grouping component (5) arranged to additively compose said offset and modulated secondary pulses into a single pulse, called the terminal pulse; said terminal pulse being a laser pulse of duration greater than the duration of the initial pulse.
[Revendication 2] Dispositif selon l’une quelconque des revendications précédentes, caractérisé en ce que l’oscillateur laser (1) est agencé de sorte que l’impulsion laser présente un spectre dont la largeur à mi-hauteur est inférieure à 1 nm. [Claim 2] Device according to any one of the preceding claims, characterized in that the laser oscillator (1) is arranged so that the laser pulse presents a spectrum whose width at half maximum is less than 1 nm.
[Revendication 3] Dispositif selon l’une quelconque des revendications précédentes, caractérisé en ce que l’oscillateur laser (1) est agencé de sorte que l’impulsion laser présente une longueur d’onde sensiblement de 1,5 micromètres ou de 2 micromètres ou de 1030 nanomètres ou 1064 nm.[Claim 3] Device according to any one of the preceding claims, characterized in that the laser oscillator (1) is arranged so that the laser pulse has a wavelength substantially of 1.5 micrometers or 2 micrometers or 1030 nanometers or 1064 nm.
[Revendication 4] Dispositif selon l’une des revendications précédentes, caractérisé en ce que l’oscillateur laser (1) comprend une diode laser à rétroaction répartie. [Claim 4] Device according to one of the preceding claims, characterized in that the laser oscillator (1) comprises a laser diode with distributed feedback.
[Revendication 5] Dispositif selon l’une quelconque des revendications précédentes, ca- ractérisé en ce que chaque canal de propagation (41, 42, 43, 44) comporte au moins une fibre optique. [Claim 5] Device according to any one of the preceding claims, ca- characterized in that each propagation channel (41, 42, 43, 44) comprises at least one optical fiber.
[Revendication 6] Dispositif selon l’une quelconque des revendications précédentes, caractérisé en ce que les canaux de propagation (41, 42, 43, 44) et les composants de séparation (2, 201, 202) et de regroupement (5, 501, 502), sont agencés de sorte que les profils des impulsions décalées et modulées se recouvrent d’au moins 10 % de leur largeur à mi-hauteur. [Claim 6] Device according to any one of the preceding claims, characterized in that the propagation channels (41, 42, 43, 44) and the separation (2, 201, 202) and grouping (5, 501) components , 502), are arranged so that the profiles of the shifted and modulated pulses overlap by at least 10% of their width at half height.
[Revendication 7] Dispositif selon l’une quelconque des revendications précédentes, caractérisé en ce que l’oscillateur laser (1) est agencé de sorte que l’impulsion initiale comporte une dérive de fréquence pendant la durée de cette impulsion et en ce qu’il comprend au moins un composant optique agencé pour modifier la dérive de fréquence d’une impulsion secondaire se propageant dans l’un des canaux de propagation (41, 42, 43, 44). [Claim 7] Device according to any one of the preceding claims, characterized in that the laser oscillator (1) is arranged so that the initial pulse includes a frequency drift during the duration of this pulse and in that it comprises at least one optical component arranged to modify the frequency drift of a secondary pulse propagating in one of the propagation channels (41, 42, 43, 44).
[Revendication 8] Dispositif selon l’une quelconque des revendications précédentes, caractérisé en ce que au moins l’un des canaux de propagation (41, 42, 43, 44) comporte un composant de modulation en puissance (31, 32, 33, 34, 301, 302, 303, 304) apte à ajuster la puissance de l’impulsion secondaire qui s’y propage. [Claim 8] Device according to any one of the preceding claims, characterized in that at least one of the propagation channels (41, 42, 43, 44) comprises a power modulation component (31, 32, 33, 34, 301, 302, 303, 304) capable of adjusting the power of the secondary pulse which propagates there.
[Revendication 9] Dispositif selon l’une quelconque des revendications précédentes, caractérisé en ce que le composant de séparation (2, 201, 202), les canaux de propagation (41, 42, 43, 44), le composant de modulation (31, 32, 33, 34, 301, 302, 303, 304) et le composant de regroupement (5, 501, 502) forment un premier étage optique du dispositif, en ce qu’il comprend un deuxième étage optique comportant un composant de séparation (202), des canaux de propagation (41, 42, 43, 44), un composant de modulation (303, 304) et un composant de regroupement (502), le deuxième étage optique étant connecté en série avec le premier étage optique de sorte que le composant de séparation (202) du deuxième étage optique reçoive l’impulsion terminale composée par le composant de regroupement (501) du premier étage optique. [Claim 9] Device according to any one of the preceding claims, characterized in that the separation component (2, 201, 202), the propagation channels (41, 42, 43, 44), the modulation component (31 , 32, 33, 34, 301, 302, 303, 304) and the grouping component (5, 501, 502) form a first optical stage of the device, in that it comprises a second optical stage comprising a separation component (202), propagation channels (41, 42, 43, 44), a modulation component (303, 304) and a grouping component (502), the second optical stage being connected in series with the first optical stage of so that the separation component (202) of the second optical stage receives the terminal pulse composed by the grouping component (501) of the first optical stage.
[Revendication 10] Dispositif selon l’une quelconque des revendications précédentes, caractérisé en ce qu’il comporte une enceinte isolante apte à isoler thermiquement et/ou mécaniquement les composants de séparation (2, 201, 202), de modulation (31, 32, 33, 34, 301, 302, 303, 304) et de regroupement (5, 501, 502). [Claim 10] Device according to any one of the preceding claims, characterized in that it comprises an insulating enclosure capable of thermally and/or mechanically isolating the separation components (2, 201, 202), modulation components (31, 32 , 33, 34, 301, 302, 303, 304) and grouping (5, 501, 502).
PCT/EP2024/051581 2023-01-27 2024-01-24 Device for generating stretched laser pulses with a modulated profile WO2024156721A1 (en)

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