Device for generating stretched laser pulses with modulated profile

Abstract

A light device (6) emitting a laser pulse comprising: a laser oscillator (1) emitting a laser pulse, called the initial pulse; a component (2) 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 (41, 42, 43, 44), each propagation channel (41, 42, 43, 44) being arranged to temporally shift the secondary pulse which propagates 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) arranged to adjust the power of at least one of said secondary pulses according to a predetermined setpoint;a pulse grouping component (5, 501, 502) arranged to additively compose said shifted 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. Figure to be published with the abstract: Fig. 1.;

Description

Title of the invention: Device for generating stretched laser pulses with modulated profile Technical field.

[0001] The invention relates to the technical field of laser devices delivering short or ultra-short pulses, and more particularly pulses with a fine spectrum of less than one nanometer and with a pulse duration from 100 picoseconds and up to durations of the order of a nanosecond.

[0002] The subject of the invention is a device for generating laser pulses of duration 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 pulsed laser source adaptable according to the concrete needs of the fields of application. State of the art.

[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 the pulse generation methods commonly implemented, 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 current-modulated semiconductor lasers. Therefore, these laser pulse generation methods do not make it possible to achieve this range of pulse duration or to precisely control the temporal shape of said pulses.

[0004] The so-called "phase mode locking" technique makes it possible, through a stretching system, to generate pulses in the range of interest, namely, from more than 100 picoseconds and up to values ​​of the order of a nanosecond; but does not allow the temporal profile of the pulses to be controlled. In addition, this technique requires a complex stretching system and only works with pulses of relatively broad spectrum, thus making the stretching of pulses with a fine spectrum, in particular of the order of 100 picometers, incompatible.

[0005] Pulse generation by gain switching 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 allow the temporal shape of the pulses or the phases of said pulses to be controlled.

[0006] Furthermore, certain applications requiring laser pulses in this range of duration also require a laser wavelength in the visible or ultraviolet spectrum. These wavelengths are generally achieved by starting with an infrared laser pulse, particularly with a wavelength around 1 micrometer, and using nonlinear crystals to perform wavelength conversion. However, the phase matching achieved in these nonlinear crystals for these conversions has limited spectral acceptance, which can be problematic when the laser source spectrum is too broad. Therefore, it is often necessary to have a narrow spectrum laser source, typically less than 100 picometers FWHM, to be able to effectively use nonlinear crystals for the generation of pulses in the range of 100 picoseconds to 500 picoseconds.

[0007] It is known that the profile of a laser pulse can have a significant impact on its interaction with matter, 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] It is possible to generate very short laser pulses with a square profile using 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] It may be noted as an example that the generation of square pulses is particularly useful for maximizing the efficiency of non-linear conversions.

[0010] The invention therefore falls within this context and seeks to resolve all of the aforementioned drawbacks. Thus, the invention seeks to propose a device for generating, from a laser source delivering short pulses, laser pulses of a duration greater than the duration of the pulses delivered by the source, in particular having a duration greater than 50 picoseconds, or even greater than 100 picoseconds, or even greater than 10 nanoseconds; with control over the time profile of said pulses and with a potentially fine spectrum. Presentation of the invention.

[0011] For these purposes, the invention relates to a light device emitting a laser pulse comprising: • a laser oscillator emitting a laser pulse, called the initial pulse; • 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 shift the secondary pulse which propagates therein by a given amount of time, in particular 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 shifted and modulated secondary pulses into a single pulse, called a terminal pulse; said terminal pulse being a pulse of duration greater than the duration of the initial pulse.

[0012] The invention thus proposes to generate, from an initial pulse of duration D1, a pulse of duration D2 greater than the duration of the initial pulse D1 by combining a set of secondary pulses shifted in time and modulated in power so that the effects of shifting and modulation of each of the secondary pulses combine when grouping the shifted and modulated secondary pulses, in particular in power and / or in spectral characteristics, in order to obtain a terminal pulse having a predefined profile, as well as a duration greater than that of the initial pulse.

[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] In the present invention, the term "spectrum" of a laser pulse means the distribution of the energy of the pulse as a function of the frequency, or equivalently, the distribution of the energy of the pulse as a function of the wavelength.

[0015] In the present invention, the term "frequency drift" of a laser pulse means a change in the frequency of light over time within said pulse. Such a frequency drift may be positive, negative or zero.

[0016] In the present invention, the term "profile" of a laser pulse means the graph of the intensity, or a function thereof, of said laser pulse over time.

[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 is the amount of energy emitted by the laser per unit of time.

[0018] In the present invention, the term "full width at half maximum" of a laser pulse is understood to mean the duration during which its optical power is greater than half of its peak power.

[0019] In the present invention, the term "interference noise" means one or more unwanted interferences that disturb the temporal profile of the terminal pulse with respect to the desired profile.

[0020] Advantageously, the shifting of the secondary pulses can be achieved by means of optical fibers of distinct lengths. Indeed, the travel time of the length of an optical fiber is directly proportional to the length of said fiber.

[0021] Advantageously, the different propagation channels may 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 propagates, thus making it possible to appropriately shift the secondary pulses.

[0022] Preferably, the propagation channels may be optical fibers made of glass, plastic or silica.

[0023] Advantageously, the separation component, the propagation channels, the modulation component and the regrouping 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] If desired, one or more of the secondary pulses may 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 also capable of generating replicas of said initial pulse.

[0025] 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] Advantageously, the grouping component may comprise flat or concave reflection mirrors, converging or diverging lenses, separating blades, optical fibers, components based on optical fibers such as fiber couplers.

[0027] 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] 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] Advantageously, the spectrum of the terminal pulse has a half-width of less than 100 picometers. By doing so, wavelength conversion in non-linear crystals is achieved efficiently.

[0030] 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 the order of ten nanoseconds with a controlled shape, and thus to eliminate in particular undesirable effects such as the Brillouin effect in optical fibers. Embodiments of the invention

[0031] In one embodiment of the invention, the laser oscillator comprises a distributed feedback laser diode.

[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] In an alternative embodiment of the invention, the laser oscillator comprises a mode-locked laser pulse source.

[0034] 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] 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] 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 of substantially 1.5 micrometers, in particular 1550 nanometers, or 2 micrometers, in particular 2100 nanometers.

[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 of substantially 1030 nanometers or 1064 nanometers.

[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 by laser pulses of these wavelengths.

[0039] 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] Advantageously, laser pulses whose wavelength is in the visible spectrum are particularly advantageous for micromachining plastic.

[0042] Advantageously, the laser pulses with a wavelength of 1030 nanometers and those of 1064 nanometers have the property of being weakly attenuated in the optical fibers, which makes these wavelengths particularly interesting for preserving the power along 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, in particular the cutting and modification of materials such as glass, metal, and plastic.

[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 for said laser oscillator, said control signal being an instruction for generating said initial pulse.

[0044] Advantageously, the oscillator controller 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] 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 and modulated secondary pulses is free of interference noise.

[0046] Advantageously, the suppression of interference noise makes it possible to improve the profile and stability of the terminal pulse.

[0047] In one embodiment of the invention, alternative or cumulative, 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] Advantageously, the combination of the continuous and discontinuous periodic components makes it possible to separate long-term and short-term effects, making it possible to optimize the operating parameters of the laser oscillator and the performance of the latter, in particular by adjusting the frequency and amplitude of the periodic component.

[0049] Advantageously, the combination of the continuous and discontinuous periodic components makes it possible to synchronize the laser oscillator with other systems by 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 regrouping components are arranged so that the profiles of the shifted and modulated pulses overlap by at least 10% of their width at half-maximum.

[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-maximum, it is ensured that their superposition is sufficiently low to minimize these undesirable effects.

[0052] In an alternative or cumulative embodiment of the invention, the laser oscillator is arranged so that the initial pulse comprises a frequency drift during the duration of this pulse. Where appropriate, 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] Advantageously, the modification of the frequency drift of a secondary pulse provides an additional means of modulating the terminal pulse, resulting from the grouping of all the shifted and modulated secondary pulses.

[0054] Advantageously, the modification of the frequency drift of a secondary pulse may in particular be obtained by using diffraction gratings, prisms, dispersive fibers or variable pitch Bragg gratings.

[0055] In an alternative or cumulative embodiment of the invention, each transmission channel comprises at least one optical fiber.

[0056] Advantageously, the optical fibers generate a very low power loss and a low degradation of the laser pulse which propagates therein, which makes it possible to efficiently transmit said laser pulses over long distances. Thus, in the case where the pulse shift is obtained by using channels of different lengths, the use of propagation channels made of optical fibers makes it possible to preserve the quality and the power of the secondary pulses until the moment when the latter will be grouped by the grouping component.

[0057] Advantageously, 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] 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 chosen power gain or loss so that the terminal pulse has a predetermined profile.

[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 temporal profile of the terminal pulse obtained during the additive composition of these secondary pulses. It is understood, 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] 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] Advantageously, this embodiment makes it possible to reduce the size of the device by combining the separation and modulation components previously mentioned in a single component.

[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] Advantageously, the fact of introducing the modulation component within one of the propagation channels makes it possible to carry out the modulation at 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] Advantageously, the power modulation component may in particular be arranged to increase or decrease the power of the secondary pulse on which it acts.

[0065] Advantageously, the propagation channel comprises several modulation components along the propagation channel.

[0066] Advantageously again, the power modulation component may in particular be a passive optical component such as a partially reflecting mirror, a section of optical fiber subjected to mechanical disturbance, a partially reflecting Bragg grating, a passive optical assembly such as an “L / 2 wave plate + polarizer” assembly or an active component such as a liquid crystal modulator, an electro-optical modulator, an acousto-optical modulator or even a semiconductor modulator.

[0067] In an alternative or cumulative embodiment of the invention, at least one of the propagation channels comprises an intensity filter for the secondary pulse which propagates there.

[0068] Advantageously again, the intensity filter may 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] Advantageously, the intensity filters may in particular be manufactured from 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] In an alternative or cumulative embodiment of the invention, at least one of the propagation channels comprises a spectral filter.

[0071] Advantageously, a propagation channel comprising a spectral filter makes it possible to select a precise wavelength range of the secondary pulse which propagates therein, in particular adapted to finely control the spectrum of the final pulse resulting from the grouping of the shifted and modulated secondary pulses.

[0072] In an alternative or cumulative embodiment of the invention, the separation component, the propagation channels, the modulation component and the regrouping component form a first optical stage of the device, such that a second optical stage comprises: a separation component, propagation channels, a modulation component and a regrouping component, the second optical stage being connected in series with the first optical stage such that the separation component of the second optical stage receives the terminal pulse composed by the regrouping component of the first optical stage.

[0073] 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] Advantageously, the invention may comprise a number N of optical stages connected in a network and such that a terminal pulse of a given stage serves as the initial pulse of another stage. The N stages may be arranged in any network configuration, comprising all or part of the network in series and / or parallel connection.

[0075] In an alternative or cumulative embodiment of the invention, the device makes it possible to modulate the secondary pulses in phase and / or in amplitude through at least one disturbing element of the propagation channels, in particular in the case of propagation channels made of 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 the secondary pulses allows for increased flexibility in applications where these pulses are used.

[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 component and the grouping component.

[0077] The propagation of secondary pulses in different propagation channels occurs with slightly different phase variations, these variations can be amplified by disturbances, in particular thermal ones, which can cause interference and significant modifications of the terminal pulse.

[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 disturbances, in particular radiative and / or convective. Furthermore, the thermal insulation makes it possible to improve the quality of the terminal pulse by avoiding amplifying interference effects intrinsic to the device.

[0079] Advantageously, the insulating enclosure may in particular be made of heat-resistant materials, in particular sheets or plates of aluminum and / or copper, ceramics such as alumina and silicon carbide or even composite materials, in particular based on carbon fibers. Advantageously, the insulating enclosure may in particular be made of pressure-resistant materials and may be designed to minimize external vibrations and shocks, in particular rubber and / or foam, for example, in the form of pads or pads.

[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] 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 may in particular carry out a frequency doubling.

[0082] The foregoing description clearly explains how the invention makes it possible to achieve the objectives it has set itself, namely to produce a laser pulse of length between 100 picoseconds and 500 picoseconds with control over the pulse profile and without limitation of the spectrum. Brief description of the figures.

[0083] Other advantages and characteristics of the present invention are now described with the aid of examples which are purely illustrative and in no way limitative of the scope of the invention, and from the appended drawings, drawings in which the various figures represent:

[0084] [Fig. 1] represents, schematically and partially, a light device delivering a laser pulse according to an embodiment of the 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] represents, schematically and partially, a time graph describing the typical profile of the terminal laser pulse, according to an embodiment of the invention.

[0087] [Fig.4] represents, schematically and partially, a light emitting device a laser pulse and comprising two optical stages according to one embodiment of the invention.

[0088] In the following description, elements that are identical, by structure or by function, appearing in different figures retain, unless otherwise specified, the same references. Description of the embodiments.

[0089] [Fig.l] shows, according to one embodiment of the invention, a light device 6 emitting a laser pulse comprising:

[0090] a laser oscillator 1 emitting an initial pulse;

[0091] a separation component 2 of the initial pulse into four pulses is secondary; each of said secondary pulses is transmitted to a dedicated propagation channel 41, 42, 43, 44; each of said propagation channels is arranged to time shift the secondary pulse propagating therein for a given amount of time;

[0092] four power modulation components 31, 32, 33, 34 arranged to adjust the power of the secondary pulses according to a predetermined setpoint;

[0093] a grouping component 5 arranged to additively compose said shifted 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] This example is given as a non-limiting example; other geometric configurations may be designed without departing from the scope of the present invention. In particular, the number of propagation channels and the number of power modulation components, their arrangement with respect to the separation component and / or the grouping component, may be varied.

[0095] In the example described, the laser oscillator 1 comprises a distributed feedback laser diode.

[0096] Without restricting the scope of the invention, the laser oscillator 1 may alternatively comprise a mode-locked laser pulse source.

[0097] 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 may be substantially equal to 1064 nm.

[0098] The light device 6 comprises a controller of the laser oscillator 1 (not shown) arranged to generate a control signal for said laser oscillator 1, said control signal being an instruction for generating the initial pulse.

[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 of interference noise.

[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] The propagation channels 41, 42, 43, 44 and the separation 2 and regrouping 5 components are arranged so that the profiles of the shifted and modulated pulses overlap by at least 10% of their width at half-height.

[0102] The laser oscillator 1 is arranged so that the initial pulse has a frequency drift during the duration of this pulse.

[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] Each transmission channel 41, 42, 43, 44 comprises at least one optical fiber.

[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] The propagation channels 41, 42, 43, 44 comprise an intensity filter (not shown) of the secondary pulse which propagates there.

[0107] The propagation channels 41, 42, 43, 44 comprise a spectral filter (not shown) of the secondary pulse which propagates there.

[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] [Fig.2] shows the time graph describing the typical profile of the initial laser pulse, according to one embodiment of the invention. The pulse profile may in particular take the form of a Gaussian distribution, a hyperbolic secant, or more generally a Gumbel or Weibull distribution.

[0110] The initial pulse profile has a half-height duration of approximately 50 picoseconds and has a rising edge with a slope significantly lower than that of the falling edge.

[0111] This typical profile corresponds to the profile of a laser pulse emitted by the laser oscillator 1 and has a wavelength of substantially 1030 nanometers according to one embodiment of the invention or 1064 nanometers according to another embodiment.

[0112] [Fig.3] shows the time graph describing the typical profile of the terminal laser pulse, according to one embodiment of the invention.

[0113] The profile of the terminal pulse of [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 of [Fig. 3] does not include interference noise and is of a shape substantially similar to a square pulse of 180 picoseconds duration, a duration notably greater than the duration of the initial pulse represented in [Fig. 2].

[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 free of interference noise because, 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 time-shifted secondary pulses.

[0115] [Fig.4] shows a light device emitting a laser pulse and comprising two optical stages according to one embodiment of the invention.

[0116] The separation component 201, the propagation channels (not shown), the modulation components 301, 302 and the regrouping component 501 form a first optical stage of the device, such that a second optical stage comprises a separation component 202, propagation channels (not shown), two modulation components 303, 304 and a regrouping component 502, the second optical stage being connected in series with the first optical stage such that the separation component 202 of the second optical stage receives the terminal pulse composed by the regrouping component 501 of the first optical stage.

[0117] The light device of [Fig.4] also comprises a receiver 600 of the terminal pulse.

[0118] The optional features of the device of [Fig.l] previously described are also applicable to the device of [Fig.4].

[0119] The device comprises an insulating enclosure (not shown) capable of thermally and / or mechanically insulating the separation 201, 202, modulation 301, 302, 303, 304 and grouping 501, 502 components.

[0120] In any event, 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, other geometric arrangements of the components of the device may be considered, as well as other laser emission sources and other materials for producing the propagation channels.

Claims

Claims

1. Light device (6) emitting a laser pulse comprising: a. a laser oscillator (1) emitting a laser pulse, called the initial pulse, the laser oscillator (1) being arranged so that the initial pulse has a frequency drift during the duration of this 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 therein by a given amount of time, in particular distinct from those of the other propagation channels (41, 42, 43, 44); c. 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. 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); e. a pulse grouping component (5) arranged to additively compose said shifted and modulated secondary pulses into a single pulse, called a terminal pulse; said terminal pulse being a laser pulse of duration greater than the duration of the initial pulse characterized in that the separation component, the propagation channels, the modulation component and the regrouping component are arranged so that the polarizations of the terminal pulse and the secondary pulses are identical to the polarization of the initial pulse and in that the light device comprises a controller of the laser oscillator, arranged to generate a control signal defining a time profile of the initial pulse such that the additive composition, performed by the grouping component, of the shifted and modulated secondary pulses is free from interference noise.

2. 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 spectrum whose width at half-maximum is less than 1 nm.

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 of substantially 1.5 micrometers or 2 micrometers or 1030 nanometers or 1064 nm.

4. Device according to one of the preceding claims, characterized in that the laser oscillator (1) comprises a distributed feedback laser diode.

5. Device according to any one of the preceding claims, characterized in that each propagation channel (41, 42, 43, 44) comprises at least one optical fiber.

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 regrouping (5, 501, 502) components are arranged so that the profiles of the shifted and modulated pulses overlap by at least 10% of their width at half-height.

7. 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 therein.

8. 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 regrouping 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 regrouping 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 component grouping (501) of the first optical stage.

9. Device according to any one of the preceding claims, characterized in that it comprises an insulating enclosure capable of thermally and / or mechanically insulating the separation (2, 201, 202), modulation (31, 32, 33, 34, 301, 302, 303, 304) and grouping (5, 501, 502) components.

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