Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
  • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
  • H01S3/005—Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping
  • H01S3/0057—Temporal shaping, e.g. pulse compression, frequency chirping
• • G—PHYSICS
  • G02—OPTICS
  • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
  • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
  • G02F1/35—Non-linear optics
  • G02F1/353—Frequency conversion, i.e. wherein a light beam is generated with frequency components different from those of the incident light beams
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
  • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
  • H01S3/005—Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping
  • H01S3/0092—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
  • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
  • H01S3/02—Constructional details
  • H01S3/025—Constructional details of solid state lasers, e.g. housings or mountings
  • H01S3/027—Constructional details of solid state lasers, e.g. housings or mountings comprising a special atmosphere inside the housing
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
  • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
  • H01S3/23—Arrangements of two or more lasers not provided for in groups H01S3/02 - H01S3/22, e.g. tandem arrangements of separate active media
  • H01S3/2308—Amplifier arrangements, e.g. MOPA

Definitions

• the present invention generally relates to the field of laser systems and in particular to light pulse compression systems.
• Frequency drift amplification (or CPA for “Chirped Power Amplification” according to the Anglo-Saxon designation of origin) is a technique regularly used in laser systems involving ultrashort laser pulses.
• a light pulse is stretched temporally before amplification to cause an extension of the duration of the light pulse.
• the stretched pulse is then amplified in an optical amplifier device.
• a compressor compresses the amplified pulse in order to obtain a light pulse having the same pulse duration as the initial duration.
• a temporally stretched light pulse can be represented very schematically by a series of wave fronts shifted temporally (or longitudinally according to the convention usually used). In other words, the wavefronts lag behind each other.
• Such a schematic representation is used here only for the purposes of explanation and illustration in the appended figures.
• the spectrum of a light pulse being generally continuous, a stretched light pulse generally presents a continuum of wave fronts.
• the compression of a light pulse can also be represented schematically by a spatial and temporal superposition (also called spatial and temporal overlap) of the wave fronts associated with the spectrum of the light pulse.
• a compressed light pulse can be used in light-matter interaction applications, for example by interaction with a nonlinear optical crystal under very specific conditions, in particular spectral acceptance, phase agreement, quality beam and focusing quality. Furthermore, it is desirable that the excitation wave (or pump wave) and the generated signal wave overlap spatially (or transversely) and temporally (or longitudinally) during their propagation. in the interaction zone. However, the light-matter interaction process is limited by a deterioration (or "walk off" in Anglo-Saxon terminology) of the spatial and temporal overlap between the wave of the excitation light beam and another wave, for example of the signal generated as the light beam propagates through the material.
• the propagation of a temporally compressed light pulse of ultra-short duration and/or high peak power in different media (solid, liquid or gas) between the compressor and the desired interaction zone is associated with numerous undesirable or damaging effects for the final application targeted by the use of such light pulses.
• This propagation of the light pulse at the output of the compressor generally induces a degradation of the quality of the light beam and therefore of the quality of temporal and spatial focusing in the desired interaction zone.
• This publication uses a device for tilting the wavefront comprising a diffraction grating and a device for shaping the inclined wavefront comprising an optical imaging system making it possible to adapt the dimension and the inclination of the wavefront of the pulse to the intended application. Tilting the wavefront allows for greater spatial and temporal superposition between the pump wave and the signal in the nonlinear crystal and thus to exceed the limits in spatial and temporal overlap in the nonlinear crystal.
• such a device for tilting the wavefront and shaping has losses which can be of the order of 75%.
• the dimensions of the tilting device by diffraction grating and of the optical imaging system must be adapted to the size of the propagating beam, which increases the total size of the system.
• the present invention proposes to improve light pulse compression systems and in particular to limit the overall losses induced by such a system while reducing the size optical components used and the size of the overall system.
• a system for compressing light pulses emitted by a light source comprising a dispersive optical system adapted to receive an incident light pulse having a straight incident wavefront with positive spectral dispersion , said dispersive optical system being designed to provide at an object point a temporally compressed light pulse having an inclined wavefront, said dispersive optical system being designed to angularly disperse a direction of propagation of the incident light pulse by at most four diffractions as a function of the spectral dispersion of the incident light pulse, so as to form at the object point the temporally compressed light pulse with an inclined wavefront and angularly dispersed.
• the temporally compressed light pulse obtained at the output of the dispersive optical system has both an inclined wavefront and an angular dispersion.
• the implementation of the dispersive optical system is simpler than a conventional compressor because it only involves at most four diffractions. This then makes it possible to minimize the area in which the light pulse is compressed.
• this reduction, or even the disappearance, of the zone in which the pulse is compressed makes it possible to limit the temporal and spatial degradation of the light beam (therefore maintaining the quality of the light beam and therefore strongly limiting the losses of the compression system).
• This then leads to greater freedom in implementing the compression system, particularly with regard to its sizing. That ultimately makes it possible to reduce the costs involved in manufacturing such a system and to improve the efficiency of the dispersive optical system.
• the temporally compressed light pulse with a wavefront inclined at the object point is dispersed angularly and temporally upstream and downstream of the object point;
• the dispersive optical system comprises three diffraction gratings arranged in series on the path of the incident light pulse, each diffraction grating of the dispersive optical system being designed to angularly disperse the direction of propagation of the incident light pulse as a function of the spectral dispersion of the incident light pulse;
• the three diffraction gratings each have a first dispersion
• the dispersive optical system comprises a single diffraction grating and an optical element configured to angularly disperse a direction of propagation of the incident light pulse by at most three successive diffractions on said diffraction grating;
• said optical element comprises a retro-reflector prism or a mirror optical system
• a mirror is provided disposed at the object point or upstream of said object point, said mirror being positioned to reflect the temporally compressed light pulse of inclined wavefront;
• - another diffraction grating is provided arranged at the object point or upstream of said object point, said other diffraction grating being positioned to adjust the angle of inclination of the wave front of the temporally compressed light pulse of front d inclined wave;
• an optical imaging system configured to form an image of the temporally compressed light pulse with an inclined wavefront and dispersed angularly at an image point and to form at this image point a spatially shaped, compressed light pulse temporally and with a wavefront inclined following a determined inclination;
• the optical imaging system comprises a final diffraction grating arranged at the image point in the plane of the inclined wavefront of the shaped light pulse spatially, temporally compressed and with a rectified wavefront, said last diffraction grating presenting the first dispersion.
• the invention also proposes a frequency drift laser amplifier system comprising a source of light pulses and a compression system as defined above, the source comprising an optical amplifier system arranged upstream of the compression system.
• the invention also relates to an optical parametric amplification system comprising an optical parametric amplifier and a compression system as defined above, the optical parametric amplifier being arranged upstream of the compression system.
• the invention also relates to a method for compressing light pulses emitted by a light source comprising steps of:
• a dispersive optical system of a temporally compressed light pulse having an inclined wavefront
• said dispersive optical system being designed to angularly disperse a direction of propagation of the incident light pulse by at most four diffractions depending on of the spectral dispersion of the incident light pulse, so as to form at an object point the temporally compressed light pulse with an inclined wavefront and angularly dispersed.
• Figure 1 is a schematic representation of a system for generating a compressed pulse with an inclined wavefront according to the invention
• Figure 2 schematically represents a first embodiment of a system for generating a compressed pulse with an inclined wavefront according to the invention
• FIG. 3 schematically represents a second embodiment of a system for generating a compressed pulse with an inclined wavefront according to the invention
• FIG. 4 schematically represents a third embodiment of a system for generating a compressed pulse with an inclined wavefront according to the invention
• Figure 5 schematically represents an example of use of a system for generating a compressed pulse with an inclined wavefront according to the invention.
• Figure 1 schematically represents a system 1 for generating a compressed pulse with an inclined wavefront according to the invention.
• This system 1 for generating a compressed pulse with an inclined wavefront comprises a light source 2 and a compression system 5.
• the light source 2 is designed to generate an incident light pulse 100.
• the light source 2 comprises for example an oscillator generating a source pulse, a stretcher and an optical amplifier system.
• Light source 2 generally does not include a compressor.
• the light source 2 may comprise for example an optical parametric amplifier, denoted OPA (for “Optical Parametric Amplifier”) which generates a beam of variable wavelength.
• OPA optical Parametric Amplifier
• the incident light pulse 100 here presents a straight incident wavefront with positive spectral dispersion.
• the incident light pulse 100 is stretched temporally.
• k a direction of propagation
• the wavefronts 1001, 1002, 1003 of the incident light pulse 100 are shifted temporally as a function of the dispersion applied spectral.
• the spectral dispersion (quantified for example in femtosecond squared (fs 2 ) or in picosecond per nanometer (ps/nm)) is here determined as a function of the pulse duration.
• this stretched pulse duration is for example between 100 picoseconds (ps) and 1 nanosecond (ns).
• FIG. 1 shows the incident wavefronts 1001, 1002, 1003 associated respectively with three distinct spectral components of the same incident light pulse 100. It should nevertheless be noted here that the incident wavefronts are made up of a continuum of spectral components (the discretization of the spectral components is carried out here for the sake of understanding the invention).
• spectral component of a light pulse means a part of a light pulse located in a narrow band of wavelength or narrow band of optical frequency determined within the band spectral, respectively of the optical frequency range associated with the light pulse.
• the incident light pulse 100 extends over a wavelength range between 700 and 900 nanometers (nm).
• the compression system 5 comprises a dispersive optical system 10 and, optionally, an optical imaging system 15.
• Figures 2 to 4 represent three examples of embodiment of the compression system 5 conforming to to the invention.
• the dispersive optical system 10 receives as input the incident light pulse 100 emitted by the light source 2.
• the dispersive optical system 10 is designed to provide as output, at an object point A, a temporally compressed light pulse 110 having a inclined emergent wavefront.
• the dispersive optical system 10 is adapted to angularly disperse the direction of propagation of the incident light pulse 100 by at most four successive diffractions.
• the temporally compressed light pulse 110 with an inclined wavefront is formed at an object point A.
• this temporally compressed light pulse 110 with an inclined wavefront is angularly dispersed. More precisely, the temporally compressed light pulse 110 with an inclined wavefront is angularly dispersed upstream and downstream of the object point A and is superimposed at the level of the object point A.
• the wave fonts 1101, 1102, 1103 associated respectively with the different spectral components of the temporally compressed light pulse 110 are superimposed spatially and temporally on the object point A. More precisely, the wave fronts 1101, 1102, 1103, are superimposed in a plane which passes through the object point A. In addition, these wave fronts 1101, 1102, 1103 superimposed spatially and temporally on the object point A, propagate along distinct propagation directions k lt k 2 , k 3 respectively upstream and downstream of point A. Each wave front, respectively 1001, 1102, 1103 is inclined relative to its direction of propagation , respectively /, k 2 , k 3 . In other words, at the output of the dispersive optical system 10, the propagation directions k lt k 2 , k 3 are angularly dispersed as a function of the spectral dispersion of the incident light pulse 100.
• inclined wavefront means a wavefront having an angle other than 90 degrees relative to its direction of propagation.
• a tilted wavefront has an angle of inclination between 10 and 80 degrees relative to its direction of propagation.
• the tilt angle is determined depending on the application and the wavelength of use. For example, in the case of terahertz pulse radiation, this inclination angle is preferably of the order of 25 degrees.
• the dispersive optical system 10 here comprises three diffraction gratings: a first diffraction grating 11, a second diffraction grating 12 and a third diffraction grating 13 These three diffraction gratings 11, 12, 13 are arranged in series on the path of the incident light pulse 100, according to an arrangement defined by the distances between these gratings and the angles of incidence of the beams on each of these gratings.
• Each diffraction grating among the first diffraction grating 11, the second diffraction grating 12 and the third diffraction grating 13 has a first angular dispersion (identical for each of these diffraction gratings), which results in a spectral dispersion due to the optical path differences of the different spectral components.
• the number of lines per millimeter determines the angular dispersion of the diffraction grating.
• the overall dispersion of the dispersive optical system is of opposite sign to the spectral dispersion of the incident pulse.
• the incident light pulse 100 is first modified by diffraction on the first diffraction grating 11 so as to form a first intermediate light pulse 101.
• the first diffraction grating 11 induces an angular dispersion of this first intermediate light pulse 101, more precisely an angular dispersion of the direction of propagation of the wave fronts 1011, 1012, 1013 as a function of the spectral dispersion of the incident light pulse 100 and of the dispersion of first diffraction grating 11.
• Each wavefront 1011, 1012, 1013 of the first intermediate light pulse 101 propagates along a distinct propagation direction. Given the arrangement implemented, each wavefront 1011, 1012, 1013 of the first intermediate light pulse 101 is then inclined here relative to its direction of propagation between the first diffraction grating 11 and the second diffraction grating 12.
• This first intermediate light pulse 101 is then modified by diffraction on the second diffraction grating 12 so as to form a second intermediate light pulse 102.
• This second intermediate light pulse 102 no longer presents angular dispersion, but only presents dispersion spatial, more precisely a transverse spatial dispersion of the direction of propagation of the wave fronts 1021, 1022, 1023 as a function of the spectral dispersion of the first intermediate light pulse 101 and the dispersion of the second diffraction grating 12.
• the fronts d The wave 1021, 1022, 1023 of the second intermediate light pulse 102 propagate along propagation directions parallel to each other.
• the directions of propagation of the wave fronts 1021, 1022, 1023 are for example spaced apart spatially (or transversely) from each other while being parallel to each other.
• Each wavefront 1021, 1022, 1023 is for example here orthogonal with respect to its direction of propagation between the second diffraction grating 12 and the third diffraction grating 13.
• This second intermediate light pulse 102 is then in turn modified by diffraction on the third diffraction grating 13 so as to form the temporally compressed light pulse 110 with an inclined wavefront.
• the third diffraction grating 13 makes it possible to form at the object point A the temporally compressed light pulse 110 with an inclined wavefront and dispersed angularly.
• the third diffraction grating 13 diffracts the second intermediate light pulse 102 and forms a third intermediate light pulse 103 between the third grating and the object point A.
• the third intermediate light pulse 103 has wave fronts 1031, 1032 , 1033 which propagate along distinct propagation directions denoted respectively k lt k 2 , k 3 which present an angular dispersion as a function of the spatial (or transverse) dispersion of the second intermediate light pulse 102 and the dispersion of the third network of diffraction 13.
• the propagation directions k lt k 2 , k 3 converge at the object point A to form the temporally compressed light pulse 110 with an inclined wavefront.
• the fronts respective waveforms 1101, 1102, 1103 of the compressed light pulse 110 are superimposed spatially and temporally on the object point A, while being inclined with respect to their respective direction of propagation. More precisely, wavefronts
• each wavefront, respectively 1101, 1102, 1103, is inclined relative to its direction of propagation, respectively k 1 , k 2 , k 3 . It is emphasized that at object point A, the propagation directions k, k 2 , k 3 are angularly dispersed as a function of the transverse spatial spreading and the diffraction gratings used.
• the temporally compressed light pulse 110 obtained at the object point A at the output of the dispersive optical system 10 has both an inclined wavefront and an angular dispersion as a function of the spectral width of the incident light pulse and the dispersion of the first diffraction grating 11, the second diffraction grating 12 and the third diffraction grating 13.
• the wave fronts of the different spectral components of the light pulse 110 are superimposed spatially and temporally, which makes it possible to obtain at the object point A a pulse compressed temporally and having an inclined wave front.
• the position and angle of inclination of the wavefront of the temporally compressed light pulse 110 are determined by the configuration and characteristics of the diffraction gratings 11, 12, 13. However, outside point A, it that is to say upstream and downstream of point A, the light pulse generated by the dispersive system 10 is spatially dispersed in addition to its angular dispersion. For example, the inclination angle is between 10 and 80 degrees relative to the direction of propagation respectively k lt k 2 , k 3 .
• the implementation of the dispersive optical system 10 is better than that of a compressor of the prior art because the arrangement described makes it possible to minimize, or even reduce at a point in space the area in which the light pulse is compressed. In practice, this results from an implementation of the dispersive optical system that is simpler than that of a compressor of the prior art, because the dispersive optical system 10 requires at most four diffraction gratings, and preferably three diffraction gratings. .
• the use of a reduced number of diffraction grating(s) allows a reduction in diffraction losses and improves the efficiency of the dispersive optical system 10.
• the use of a reduced number of diffraction grating(s) also allows a reduction in the costs involved in the manufacture of such a system.
• the three diffraction gratings 11, 12, 13 can be replaced by three prisms or by three grisms or by a combination of three elements chosen from a diffraction grating, a prism and a grism to form at most three spectral dispersions or diffractions of the incident light pulse.
• the three successive dispersive elements each have an identical angular dispersion (as explained above). They thus have a first identical angular dispersion for each of these dispersive elements.
• the dispersive optical system 10 may comprise a single diffraction grating and an associated optical element.
• the optical element associated with a single diffraction grating is for example a prism or a retro-prism.
• the optical element can be formed by at least one mirror.
• the combination of this single diffraction grating and the optical element is also designed to angularly disperse the direction of propagation of the incident light pulse by at most three successive diffractions on the same diffraction grating (each of the three successive diffractions presenting a identical angular dispersion, here corresponding to the first angular dispersion as explained above.
• each of the three successive diffractions makes it possible to obtain an angular dispersion which is identical for the three successive diffractions), after retro-reflection on the optical element, of so as to form the compressed light pulse with an emerging wave front inclined at an object point A, this compressed pulse having an angular dispersion of its direction of propagation which is a function of the spectral dispersion of the incident light pulse and the dispersion of the single diffraction grating.
• the incident light pulse is modified by diffraction by the single diffraction grating so as to form the first intermediate light pulse.
• the latter is then directed again towards the single diffraction grating using the optical element.
• the first intermediate light pulse is again modified by diffraction by the single diffraction grating so as to form the second intermediate light pulse.
• the optical element also returns the second intermediate light pulse to the single diffraction grating so that it is also modified by diffraction in order to form the temporally compressed light pulse 110 with an inclined wavefront.
• the dispersive optical system can be formed by two diffraction gratings and the optical element previously introduced so as to form the compressed light pulse with an inclined wavefront, by at most four successive diffractions.
• the angular dispersion obtained causes the spatial spreading of the light pulse 110 compressed during its propagation after the object point A.
• the use of a reduced number of optical components makes it possible to minimize, or even reduce to a point in space, the zone in which the light pulse is compressed, and therefore to reduce losses. induced by optical components. This therefore makes it possible to improve the compactness of the compression and spatial shaping system 1.
• the compression system 5 comprises for example a mirror 16.
• This mirror 16 is designed to reflect the light pulse 110 compressed temporally.
• the mirror 16 is positioned at the object point A where the temporally compressed light pulse 110 with an inclined wavefront is formed.
• the mirror 16 can be positioned upstream or downstream of the object point A.
• the mirror 16 deflects the directions of propagation k lt k 2 , k 3 of the compressed pulse 110.
• the mirror 16 is flat.
• the return mirror 16 is optional.
• the angular dispersion of the light pulse 110 compressed locally at point A makes it possible to limit, for the further propagation of the light pulse, the spatial and temporal distortions of the light pulse likely to be induced by nonlinear optical effects in the propagation medium.
• the transverse spatial dispersion or the angular dispersion of the light pulse makes it possible to limit non-linear optical effects and degradations due to propagation in the ambient environment or on the optical components.
• the intensity of the light beam is reduced at every point in space in order to limit, or even avoid, non-linear optical effects. Indeed, in the presence of a transverse spatial dispersion or an angular dispersion of the wavefronts, they cannot superimpose.
• a reflected light pulse 160 is then obtained which is angularly dispersed by reflection of the propagation directions k lt k 2 , k 3 on the mirror 16.
• the reflected light pulse 160 is therefore angularly dispersed.
• the wave fronts 1601, 1602, 1603 of the different spectral components of the reflected light pulse 160 propagate along propagation directions corresponding respectively to the reflection of the propagation directions k lt k 2 , k 3 on the mirror 16.
• mirror 16 can be replaced by a fourth diffraction grating (not shown).
• This fourth diffraction grating makes it possible to adjust the angle of inclination of the wavefront or even to straighten the wavefront (which is therefore no longer inclined).
• This fourth diffraction grating has a dispersion different from that of the first diffraction grating 11, the second diffraction grating 12 and the third diffraction grating 13 previously introduced.
• the fourth diffraction grating is positioned upstream or at the object point A where the temporally compressed light pulse 110 with inclined wavefront is formed. Alternatively, it can be positioned upstream of object point A.
• This fourth diffraction grating deflects the propagation directions k lt k 2 , k 3 of the spectral components of the compressed pulse 110.
• the characteristics of the fourth diffraction grating are adapted to the intended application at the output of the compression system 5.
• the compression system 5 optionally comprises the optical imaging system 15 positioned at the output of the dispersive optical system 10.
• the optical imaging system 15 forms the image of the compressed light pulse 110 and makes it possible to adjust the angle of inclination of the wavefront to obtain the desired spatial and temporal superposition at an image point B distant from the object point A.
• the optical imaging system 15 allows to spatially shape the compressed light pulse with an inclined wavefront according to the intended application.
• the imaging system can for example be a magnification system, the magnification of which has an influence on the angle of inclination of the wavefront.
• the reflected light pulse 160 then propagates downstream of the mirror 16 (or the fourth diffraction grating as a variant) towards the optical imaging system 15. More precisely, the reflected light pulse 160 propagates up to an optical system 17 included in the optical imaging system 15 ( Figures 4 and 5).
• This optical system 17 is designed to shape the reflected light pulse 160 so that it can be used for the intended applications at the output of the compression system 5.
• the optical system 17 comprises for example an optical system with lens(es) or mirror(s).
• the optical components included in the optical system 17 are for example spherical optical components for focusing on a point or cylindrical optical components for focusing on a line. Cylindrical optical components are particularly advantageous because they allow implementation in the open air (while spherical optical components require working in a vacuum atmosphere).
• the optical system 17 comprises for example two optical components, each optical component being positioned in a different plane, the two planes being orthogonal to each other.
• the optical magnification of the optical system 17 makes it possible to adjust the angle of inclination of the wavefront at the image point B.
• the optical system 17 moves the temporally compressed pulse from the object point A at image point B and rotates the plane of the inclined wavefront of the temporally compressed pulse to arrange and superimpose it at the desired location depending on the application.
• the light pulse remains spatially dispersed, which makes it possible to avoid the generation of undesirable effects during the propagation of the light pulse between these two points.
• the mirror 16 (or the fourth diffraction grating as a variant) and the optical system 17 of the optical imaging system 15 make it possible to spatially and temporally superimpose the components of the reflected light pulse 160 at a point.
• image B the shaped light pulse 150 is compressed, spatially and temporally recombined and presents an inclined emerging wave front. More precisely, the wavefronts 1501, 1502, 1503 are superimposed in a plane which passes through the image point B.
• each wave front d The wave, respectively 1501, 1502, 1503, is inclined relative to its direction of propagation.
• the shaped and temporally compressed light pulse 150 also has an inclined wavefront and a dispersion angular of its direction of propagation as a function of the spectral dispersion of the incident light pulse.
• the shaped and compressed light pulse 150 can be used for the application referred to in image point B.
• the shaped and compressed light pulse 150, with an inclined wavefront inclined waveform can be used at image point B at a distance from object point A, without generating undesirable non-linear optical effects between object point A and image point B.
• Figure 5 represents a second example of a compression system 5 according to the invention.
• the optical imaging system further comprises a last diffraction grating 18.
• This last diffraction grating 18 is positioned in the optical imaging system 15 at the output of the optical system 17.
• This last diffraction grating 18 has the same dispersion as the first diffraction grating 11, the second diffraction grating 12 and the third diffraction grating 13 previously introduced.
• the last diffraction grating 18 therefore receives a shaped light pulse 150 obtained at the output of the other optical element 17.
• the last diffraction grating 18 is positioned at the level of the image point B described above, that is to say at the place where the shaped light pulse 150 is compressed, spatially and temporally recombined and presents a tilted emergent wavefront.
• the last diffraction grating 18 is planar.
• the last diffraction grating 18 is inclined so that the plane of the last diffraction grating coincides with the plane of the inclined wavefront of the shaped and compressed light pulse 150.
• This last diffraction grating 18 makes it possible to rectify the different spectral components of the shaped light pulse 150 so that they propagate along the same direction of propagation k s .
• the wave fonts 1501, 1502, 1503 superimposed spatially and temporally at the image point B propagate along the same direction of propagation k s at the output of the last diffraction grating 18.
• Each wave front, respectively 1501, 1502 , 1503 is inclined by the same non-zero angle with respect to the direction of propagation k s .
• the direction of propagation k s of the shaped and temporally compressed light pulse 180 presents no angular dispersion.
• the wavefront of pulse 180 is rectified. [0071]
• the light pulse shaped 180 and compressed with an inclined wavefront can be used from the image point B following the direction of propagation k s at any point.
• the compression and spatial shaping system according to the invention can be integrated into a frequency drift amplifier, instead of a conventional compressor, in order to generate ultra-short amplified light pulses , in particular pulses in femtosecond mode, that is to say of duration between 5 femtoseconds and 10 picoseconds.
• the compression system of the present disclosure finds applications in particular in a titanium-sapphire laser, a rare earth doped glass matrix laser, for example a ytterbium-YAG laser (Yb:YAG), a neodymium-YAG laser (Nd: YAG), a thulium-YAG laser (Tm-YAG) or an erbium-YAG laser (Er-YAG) or a neodymium-doped yttrium lithium fluoride (Nd:YLF) laser, or even in a fiber laser.
• Yb:YAG a ytterbium-YAG laser
• Nd neodymium-YAG laser
• Tm-YAG thulium-YAG laser
• Er-YAG erbium-YAG laser
• Nd:YLF neodymium-doped yttrium lithium fluoride
• the compression and spatial shaping system according to the invention can also be combined with an optical parametric amplifier for the generation of radiation of variable wavelength by generation of sum frequency (or SFG for "Sum frequency”). generation” in English terminology). Indeed, in this case, the angular dispersion of the beams makes it easier to separate the different harmonics generated.
• the compression and spatial shaping system also finds applications for the generation of terahertz radiation by interaction between a temporally compressed pulse with an inclined wavefront and a non-linear optical component.
• the compression and spatial shaping system finds advantageous applications for inverse Compton diffusion (or Thomson diffusion), where the beams cross with a high angle of incidence, so that the inclination of the front d The wave allows better superposition with a bunch of electrons.
• inverse Compton diffusion or Thomson diffusion
• the compression and spatial shaping system finds other applications for dielectric laser acceleration (or DLA for “dielectric laser acceleration” in English terminology).
• the compression and spatial shaping system 1 described above makes it possible to implement the following method of compression and spatial shaping of light pulses with an inclined wavefront.
• the light source 2 generates an incident light pulse 100.
• This incident light pulse 100 has a straight incident wavefront with positive spectral dispersion.
• This incident light pulse 100 propagates in the direction of the compression system 5, and more particularly in the direction of the dispersive optical system 10 of the compression system 5 in a direction of propagation, denoted k.
• the incident wavefront associated with each spectral component of the incident light pulse is orthogonal to the direction of propagation k.
• the incident wavefronts 1001, 1002, 1003 are orthogonal to the direction of propagation k.
• the method continues with a step during which the dispersive optical system 10 receives the incident light pulse 100.
• the dispersive optical system 10 then provides output, by at most four successive diffractions of the light pulse incident 100, the temporally compressed light pulse 110 having an inclined wavefront at an object point A.
• the temporally compressed light pulse 110 with an inclined wavefront is formed at the object point A
• the wave fronts 1101, 1102, 1103 associated with the compressed light pulse 110 are superimposed spatially and temporally at the object point A. More precisely, the wave fronts 1101, 1102, 1103 are superimposed spatially and temporally in a plane which passes through the object point A.
• wave fronts 1101, 1102, 1103 superimposed spatially and temporally at the object point A, propagate along distinct propagation directions k 1 , k 2 , k 3 respectively.
• Each wavefront, respectively 1101, 1102, 1103, is inclined relative to its direction of propagation, respectively k lt k 2 , k 3 . Consequently, this temporally compressed light pulse 110 with inclined wavefront is angularly dispersed.
• the method then continues with a step during which the compressed light pulse 110 is spatially shaped by the optical imaging system 15 in order to form an image of this temporally compressed light pulse 110 at a wave front. inclined at an image point B following a desired inclination angle.
• the light pulse obtained is the light pulse 150 shaped spatially and compressed temporally, and which has a wave front inclined at the image point B, which is the image of the point object A.
• the optical imaging system makes it possible to position the wavefront of the shaped and temporally compressed light pulse 150 to superimpose it on the desired image point B according to the application.
• the angle of inclination of the wavefront at the image point B depends in particular on the orientation of the return mirror 16 and/or the optical magnification of the optical system 17.
• the method further comprises an additional step consisting of diffracting the light pulse 150 shaped and compressed at the image point B on a diffraction grating arranged in the plane of the inclined wave front of the light pulse 150 shaped and compressed, so as to superimpose the spectral components of the light pulse 150 shaped and compressed in the same direction of propagation k s .

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• 2022
  • 2022-06-27 FR FR2206406A patent/FR3137221A1/fr active Pending
• 2023
  • 2023-06-27 KR KR1020257001829A patent/KR20250025010A/ko active Pending
  • 2023-06-27 EP EP23735324.8A patent/EP4544646A1/de active Pending
  • 2023-06-27 JP JP2024576427A patent/JP2025520785A/ja active Pending
  • 2023-06-27 WO PCT/EP2023/067504 patent/WO2024003068A1/fr not_active Ceased
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