System and method for compressing optical pulses

Abstract

The present invention relates to a system (5) for compressing optical pulses emitted by a light source (2), which is configured to receive an incident optical pulse (100) having a right-angled incident wavefront with positive spectral dispersion, and the dispersion optical system (10) is designed to deliver a temporally compressed optical pulse (110) having an inclined wavefront at an object point (A), and the dispersion optical system (10) is designed to angularly disperse the propagation direction of the incident optical pulse through a maximum of four diffractions according to the spectral dispersion of the incident optical pulse (100) to form an angularly dispersed temporally compressed optical pulse (110) having an inclined wavefront.

Description

Technical Field

[0001] The present invention relates to the field of laser systems, and more particularly, to an optical pulse amplification compression system.

[0002] More specifically, the present invention relates to a system for compressing optical pulses emitted by a light source.

Background Art

[0003] "Chirped Pulse Amplification" (CPA) is a technique commonly used in laser systems involving ultrashort laser pulses. In such a system, an optical pulse is temporally stretched before amplification, increasing the pulse duration. The stretched pulse is then amplified by an optical amplifier. At the output of the optical amplifier, a compressor compresses the amplified pulse to obtain an optical pulse with the same pulse duration as the initial one.

[0004] The temporally stretched optical pulse can be roughly represented by a succession of wavefronts that are temporally shifted (or, according to a commonly used convention, longitudinally shifted). In other words, the wavefronts are successively delayed. Such a rough representation is used herein only for the purpose of explanation and illustration in the accompanying drawings. However, as is well known, since the spectrum of an optical pulse is generally continuous, the stretched optical pulse generally has a wavefront continuum.

[0005] The compression of an optical pulse can also be roughly represented by the spatial and temporal overlap (also called spatial and temporal overlap) of the wavefronts associated with the spectrum of the optical pulse.

[0006] Compressed optical pulses can be used in applications of light-matter interaction, for example, through interaction with a nonlinear optical crystal under specific conditions including, for example, spectral allowable range, pulse tuning, beam quality, and focusing quality. Further, it is desirable that the excitation light wave (or pump light wave) and the generated signal wave overlap spatially (i.e., laterally) or temporally (i.e., longitudinally) with each other as they propagate through the interaction region. However, the process of light-matter interaction is limited by the degradation of spatial and temporal overlap (i.e., “walk-off”) between the excitation light beam wave and other waves of the signal generated, for example, when the light beam propagates in a material.

[0007] Furthermore, the propagation of a time-compressed optical pulse having an ultrashort duration and / or high peak power through different media (solid, liquid, gas) between the compressor and the desired interaction region may be undesirable or may have a harmful effect on the final application targeted by the use of such an optical pulse. This optical pulse propagation at the outlet of the compressor generally causes degradation in the temporal and spatial focusing quality of the light beam and thus in the desired interaction region.

[0008] To compensate for the optical beam propagation between the compressor and the interaction region, it may be necessary to expand the beam size to reduce the energy density up to the point of use. This requires the use of large optical components at the outlet of the compressor. Another solution is to propagate the time-compressed optical pulse in a vacuum, but this complicates the system.

[0009] In other applications for generating terahertz (THz) pulse radiation by the interaction between ultrashort optical pulses and a nonlinear material, the literature by Janos Hebling, Gabor Almasi, Ida Z. Kozma, and Jurgen Kuhl, "Velocity matching by pulse front tilting for large - area THz - pulse generation", Opt. Express Vol.10, no21, 1161 - 1166(2002) proposed introducing a wavefront tilting technique ("pulse wavefront tilt") to optimize the spatial and temporal overlap, limit its degradation, and adjust the THz radiation according to the tilt angle of the wavefront of the optical pulse in the nonlinear material.

[0010] In this publication, a wavefront tilt device is used, which includes a diffraction grating and a device for shaping the tilted wavefront including an optical imaging system, to adapt the size and tilt of the pulse wavefront to the desired application. By tilting the wavefront, it is possible to increase the spatial and temporal overlap between the pump light wave and the signal wave in the nonlinear crystal, and thus exceed the limits of spatial and temporal overlap in the nonlinear crystal.

[0011] However, such wavefront tilt and shaping devices result in losses of up to 75%. Furthermore, since the size of the tilt device by the diffraction grating and the optical imaging system must be adapted to the size of the propagation beam, the overall footprint of the system becomes large.

Summary of the Invention

Problems to be Solved by the Invention

[0012] To improve the above - mentioned drawbacks of the prior art, the present invention proposes to improve the optical pulse compression system, and in particular to limit the overall losses induced by such a system, while at the same time reducing the size of the optical components used and the overall footprint of the system.

Means for Solving the Problems

[0013] More specifically, a system for compressing optical pulses emitted by a light source has been proposed, which includes a dispersive optical system configured to receive an incident optical pulse having a collinear incident wavefront with positive spectral dispersion, and the dispersive optical system is designed to deliver, at an object point, a temporally compressed optical pulse having an inclined wavefront. The dispersive optical system angularly disperses the propagation direction of the incident optical pulse through up to four diffractions according to the spectral dispersion of the incident optical pulse, and is designed to form, at the object point, an angularly dispersed temporally compressed optical pulse 110 having an inclined wavefront.

[0014] Thus, as an advantage, the temporally compressed optical pulse obtained at the output of the dispersive optical system has both an inclined wavefront and angular dispersion.

[0015] Furthermore, the implementation of the dispersive optical system is simpler than that of conventional compressors because the diffraction included therein is at most four times. As a result, the region in which the optical pulse is compressed is reduced. As an advantage, this reduction or even disappearance of the region in which the pulse is compressed makes it possible to limit the temporal and spatial degradation of the optical beam (thus maintaining the quality of the optical beam and thus greatly limiting the losses of the compression system). This provides greater freedom especially in terms of sizing in the implementation of the compression system. This can ultimately reduce the cost involved in manufacturing such a system and improve the efficiency of the dispersive optical system.

[0016] The other non-limiting and advantageous features of the compression system according to the invention, which can be obtained individually or by any technically possible combination, are as follows.

[0017] - The temporally compressed optical pulse 110 having an inclined wavefront and angularly dispersed at the object point is angularly and temporally dispersed upstream and downstream of the object point. - The dispersive optical system includes three diffraction gratings arranged in series on the incident light pulse path, and each diffraction grating of the dispersive optical system is configured to angularly disperse the propagation direction of the incident light pulse according to the spectral dispersion of the incident light pulse. - Each of the three diffraction gratings has a first degree of dispersion. - The dispersive optical system includes a single diffraction grating and an optical element configured to angularly disperse the propagation direction of the incident light pulse through a maximum of three consecutive diffractions on the diffraction grating. - The optical element includes a retroreflective prism or a mirror optical system. - The mirror is provided at the object point or upstream of the object point, and the mirror is positioned to reflect a temporally compressed light pulse having an inclined wavefront. - Another diffraction grating is provided at the object point or upstream of the object point, and the other diffraction grating is positioned to adjust the tilt angle of the wavefront of the temporally compressed light pulse having an inclined wavefront. - The other grating has a second degree of dispersion. - An optical imaging system is provided at the image point to form an image of the angularly dispersed temporally compressed light pulse having an inclined wavefront, and at this image point, is configured to form a spatially shaped temporally compressed light pulse having an inclined wavefront with a predetermined inclination. - The optical imaging system includes a final diffraction grating arranged at the image point in the plane of the inclined wavefront of the spatially shaped temporally compressed light pulse having an upright wavefront, and the final diffraction grating has a first degree of dispersion.

[0018] The present invention also proposes a chirped pulse laser compression system including an optical pulse source and the aforementioned compression system, and the source includes an optical amplification system arranged upstream of the compression system.

[0019] The present invention also relates to an optical parametric amplification system including an optical parametric amplifier and the aforementioned compression system, and the optical parametric amplifier is arranged upstream of the compression system.

[0020] The present invention also: - Receiving an incident optical pulse having an upright incident wavefront with positive spectral dispersion; - Generating, by a dispersive optical system, a time-compressed optical pulse having an inclined wavefront, wherein the dispersive optical system is designed to angularly disperse the propagation direction of the incident optical pulse in accordance with the spectral dispersion of the incident optical pulse through up to four diffractions, and to form, at an object point, a time-compressed optical pulse 110 having an inclined wavefront and angular dispersion; The present invention relates to a method for compressing an optical pulse emitted by a light source, including the above steps.

[0021] The present invention can be better understood from the following description of the accompanying drawings, which are presented by way of non-limiting example, and how it can be implemented.

Brief Description of the Drawings

[0022]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0023] Note that in these figures, the same reference numerals may be assigned to structural and / or functional elements common to various alternatives.

[0024] FIG. 1 is a schematic diagram of a system 1 for generating a compressed pulse having an inclined wavefront according to the present invention.

[0025] This system 1 for generating a compressed pulse having an inclined wavefront includes a light source 2 and a compression system 5.

[0026] The light source 2 is designed to generate an incident light pulse 100.

[0027] In certain embodiments, the light source 2 includes, for example, an oscillator, a stretcher, and an optical amplification system that generate light pulses. The light source 2 generally does not have a compressor. Alternatively, the light source 2 can include, for example, an optical parametric amplifier (OPA) that generates an adjustable wavelength beam.

[0028] Generally, the incident light pulse 100 here has an upright wavefront with positive spectral dispersion. In other words, the incident light pulse 100 is temporally stretched. Hereinafter, the propagation direction is defined in relation to the incident light pulse 100,

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[0029] As a non-limiting example, FIG. 1 shows incident wavefronts 1001, 1002, and 1003 associated with three different spectral components of the same incident light pulse 100, respectively. However, it should be noted here that the incident wavefront is composed of a continuum of spectral components (here, the spectral components are separated for the purpose of understanding the invention).

[0030] In this specification, a spectral component is to be understood as a light pulse or a part of a light pulse that is within a predetermined narrow wavelength band or a narrow optical frequency band in a spectral band of an optical frequency range associated with the light pulse.

[0031] For example, the incident light pulse 100 extends over a wavelength range of 700 to 900 nanometers (nm).

[0032] As shown in FIG. 1, the compression system 5 includes a dispersive optical system 10 and, optionally, an optical imaging system 15. FIGS. 2 - 4 show three exemplary embodiments of the compression system 5 according to the present invention.

[0033] The dispersive optical system 10 receives, as an input, the incident light pulse 100 emitted by the light source 2. The dispersive optical system 10 is designed to provide, as an output, a temporally compressed light pulse 110 having an inclined emission wavefront at the object point A. For that purpose, the dispersive optical system 10 is configured to angularly disperse the propagation direction of the incident light pulse 100 through up to four consecutive diffractions.

[0034] Accordingly, at the output of the dispersive optical system 10, a temporally compressed light pulse 110 having an inclined wavefront is formed at the object point A. Further, this temporally compressed light pulse 110 having an inclined wavefront is angularly dispersed. More precisely, the temporally compressed light pulse 110 having an inclined wavefront is angularly dispersed upstream and downstream of the object point A and superimposed at the object point A.

[0035] In other words, the wavefronts 1101, 1102, 1103 associated with the different spectral components of the time-compressed optical pulse 110 are spatially and temporally superimposed at the object point A. More precisely, the wavefronts 1101, 1102, 1103 are superimposed in the plane through which the object point A passes. Further, these wavefronts 1101, 1102, 1103 are spatially and temporally superimposed at the object point A and propagate along different propagation directions upstream and downstream of the point A respectively

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[0036] In this specification, the "tilted wavefront" means a wavefront having an angle other than 90 degrees with respect to its propagation direction. Preferably, the tilt angle of the tilted wavefront is 10 to 80 degrees with respect to its propagation direction. The tilt angle is specified according to the application and the wavelength used. For example, in the case of terahertz pulse radiation, this tilt angle is preferably about 25 degrees

[0037] As shown in the examples depicted in FIGS. 2 to 5, in practice, the dispersive optical system 10 here includes three diffraction gratings, namely, 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 along the path of the incident light pulse 100 according to an arrangement defined by the distance between these gratings and the angle of incidence of the beam on each of these gratings. Each of the first diffraction grating 11, the second diffraction grating 12, and the third diffraction grating 13 has a first angular dispersion (the same for each of these diffraction gratings), and as a result, spectral dispersion is obtained due to the difference in the optical paths of different spectral components. The angular dispersion of the diffraction grating is determined by the number of lines per millimeter. Advantageously, the overall dispersion of the dispersive optical system has a sign opposite to that with respect to the spectral dispersion of the incident light pulse.

[0038] More specifically, as schematically shown in FIGS. 2 to 5, the incident light pulse 100 is first modulated by diffraction in the first diffraction grating 11 to form a first intermediate light pulse 101. The first diffraction grating 11 causes an angular dispersion of this first intermediate light pulse 101, more precisely, an angular dispersion of the propagation directions of the wavefronts 1011, 1012, 1013, according to the spectral dispersion of the incident light pulse 100 and the dispersion of the first diffraction grating 11. Each of the wavefronts 1011, 1012, 1013 of the first intermediate light pulse 101 propagates along different propagation directions. With this arrangement, each of the wavefronts 1011, 1012, 1013 of the first intermediate light pulse 101 is then tilted with respect to its propagation direction between the first diffraction grating 11 and the second diffraction grating 12.

[0039] This first intermediate optical pulse 101 is then modulated by diffraction at the second diffraction grating 12 to form a second intermediate optical pulse 102. This second intermediate optical pulse 102 no longer exhibits angular dispersion and has only spatial dispersion, more precisely a spatial dispersion across the propagation directions of wavefronts 1021, 1022, 1023 corresponding to the spectral dispersion of the first intermediate optical pulse 101 and the dispersion degree of the second diffraction grating 12. The wavefronts 1021, 1022, 1023 of the second intermediate optical pulse 102 propagate along propagation directions parallel to each other. As a non-limiting example, the propagation directions of the wavefronts 1021, 1022, 1023 are, for example, spatially (i.e., laterally) separated from each other and at the same time parallel to each other. Each wavefront 1021, 1022, 1023 is, for example, perpendicular here with respect to its propagation direction between the second diffraction grating 12 and the third diffraction grating 13.

[0040] This second intermediate optical pulse 102 is then also modulated by diffraction at the third diffraction grating 13 to form a time-compressed optical pulse 110 with an inclined wavefront. More precisely, the third diffraction grating 13 makes it possible to form an angularly dispersed time-compressed optical pulse 110 having an inclined wavefront at the object point A. For this purpose, the third diffraction grating 13 diffracts the second intermediate optical pulse 102 to form a third intermediate optical pulse 103 between the third grating and the object point A. The third intermediate optical pulse 103 has an angular dispersion corresponding to the spatial (i.e., lateral) dispersion of the second intermediate optical pulse 102 and the dispersion degree of the third diffraction grating 13, respectively

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[0041] Therefore, according to the present invention, as an advantageous point, the temporally compressed optical pulse 110 obtained at the object point A at the exit of the dispersive optical system 10 has both an inclined wavefront and angular dispersion according to the spectral width of the incident optical pulse and the dispersions of the first diffraction grating 11, the second diffraction grating 12, and the third diffraction grating 13. In other words, at the object point A, the wavefronts of different spectral components of the optical pulse 110 are spatially and temporally superimposed on each other, thereby obtaining a temporally compressed pulse with an inclined wavefront at the object point A. The position and inclination angle of the wavefront of the temporally compressed optical pulse 110 are determined by the configuration and characteristics of the diffraction gratings 11, 12, 13. However, outside the point A, that is, upstream and downstream of the point A, the optical pulse generated by the dispersive system 10 is spatially dispersed in addition to its angular dispersion. For example, the inclination angle is 10 to 80 degrees with respect to the propagation direction, respectively

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[0042] Furthermore, with the above-described arrangement, the region where the optical pulse is compressed can be minimized and even reduced to a single point, so the implementation of the dispersive optical system 10 is better than that of the prior art compressors. In fact, this is because the dispersive optical system 10 requires at most four diffraction gratings, preferably three, so the dispersive optical system is easier to implement than the prior art compressors. By using a smaller number of diffraction gratings, diffraction losses can be reduced and the efficiency of the dispersive optical system 10 can be improved. Also, by using a smaller number of diffraction gratings, it is possible to reduce the cost involved in manufacturing such a system.

[0043] According to a variant of the present disclosure, the three diffraction gratings 11, 12, 13 can be replaced by three prisms, three gratings, or a combination selected from diffraction gratings, prisms, and gratings that form at most three spectral dispersions or diffractions of the incident optical pulse. In these variants, each of the three consecutive dispersive elements has the same angular dispersion (as described above). They therefore have the same first angular dispersion degree for each of these dispersive elements.

[0044] Alternatively, the dispersive optical system 10 can include a single diffraction grating and an output element associated therewith. The optical element associated with the diffraction grating is, for example, a prism or a retroprism. Alternatively, the optical element can be formed of at least one mirror. This combination of a single diffraction grating and an optical element is also designed to angularly disperse the propagation direction of the incident optical pulse by at least three consecutive diffractions at the same diffraction grating (each of the three consecutive diffractions has, here as described above, the same angular dispersion degree according to the first angular dispersion degree. Thus, each of the three consecutive diffractions can obtain the same angular dispersion after recursive reflection on the optical element so that a compressed light with an inclined emission wavefront is formed on the object point A, and this compressed pulse has an angular dispersion in its propagation direction according to the spectral dispersion of the incident optical pulse and the dispersion of the single diffraction grating.

[0045] In fact, according to this alternative, the incident light pulse is modulated by diffraction by a single diffraction grating, and a first intermediate light pulse is formed. This is then directed back to the single diffraction grating by the optical element. This first intermediate light pulse is modulated again by diffraction by the single diffraction grating, and a second intermediate light pulse is formed. The optical element also returns the second intermediate light pulse to the single diffraction grating so that a time-compressed light pulse 110 with an inclined wavefront is formed, and it is also modulated by diffraction.

[0046] As an alternative, the dispersive optical system can be formed by two diffraction gratings and the aforementioned optical element so as to form a compressed light pulse with an inclined wavefront through up to four consecutive diffractions.

[0047] At the exit of the dispersive optical system 10, due to the resulting angular dispersion, the compressed light pulse 110 spreads spatially during the propagation of the compressed light pulse 110 behind the object point A.

[0048] As an advantage, by using a smaller number of optical components, the region where the light pulse is compressed can be minimized and even reduced to a single point in space, thus reducing the losses induced by the optical components. This makes it possible to improve the compactness of system 1 for compression and spatial shaping.

[0049] As shown in FIGS. 3 to 5, the compression system 5 includes, for example, a mirror 16. This mirror 16 is designed to reflect the time-compressed light pulse 110.

[0050] In fact, the mirror 16 is positioned at the object point A where an angularly dispersed time-compressed light pulse 110 with an inclined wavefront is formed. As an alternative, the mirror 16 can be positioned upstream or downstream of the object point A. The mirror 16 is in the propagation direction of the compressed pulse 110

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[0051] Advantageously, according to this embodiment, due to the angular dispersion of the locally compressed optical pulse 110 at point A, for the tracking of optical pulse propagation, the spatial and temporal dispersion of the optical pulse that is likely to be induced by the nonlinear optical effect in the propagation medium can be restricted. Outside point A, it is possible to limit the nonlinear optical effects and degradation due to propagation in the surrounding environment or on the optical components by the lateral spatial dispersion or angular dispersion of the optical pulse. In particular, the intensity of the optical beam is reduced at any point in space, and the nonlinear optical effects are restricted or avoided. In fact, when there is a lateral spatial dispersion or angular dispersion of the wavefront, these cannot be superimposed. Then, at the exit of the mirror 16, the propagation direction on the mirror 16

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[0052] Alternatively, the mirror 16 can be replaced by a fourth diffraction grating (not shown). With this fourth diffraction grating, it is possible to adjust the tilt angle of the wavefront and further to straighten the wavefront (therefore, it is in a non-tilted state). This fourth diffraction grating has a different dispersion degree from that of the aforementioned first diffraction grating 11, second diffraction grating 12, and third diffraction grating 13.

[0053] The fourth diffraction grating is positioned upstream of or at the object point A at which the temporally compressed optical pulse 110 having an inclined wavefront is formed. As an alternative, this can be positioned upstream of the object point A.

[0054] The fourth diffraction grating deflects the propagation directions

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[0055] As shown in FIGS. 4 and 5, the compression system 5 optionally includes an optical imaging system 15 positioned at the output of the dispersive optical system 10. The optical imaging system 15 forms an image of the compressed optical pulse 110, thereby making it possible to adjust the inclination angle of the wavefront and obtain a desired spatial and temporal overlap at the image point B away from the object point A. In other words, the optical imaging system 15 can spatially shape the temporally compressed optical pulse 110 having an inclined wavefront according to the target application.

[0056] The imaging system can be, for example, a magnification system, and its magnification affects the inclination angle of the wavefront.

[0057] The reflected optical pulse 160 then propagates towards the optical imaging system 15 downstream of the mirror 16 (or, as an alternative, the fourth diffraction grating). More precisely, the reflected optical pulse 160 propagates to the optical system 17 (FIGS. 4 and 5) included in the optical imaging system 15. This optical system 17 is designed to shape the reflected optical pulse 160 so that it can be used for the target application at the output of the compression system 5.

[0058] The optical system 17 includes, for example, an optical system based on lenses or mirrors. The optical components included in the optical system 17 are, for example, spherical optical components that focus on a point or cylindrical optical components that focus on a line. Cylindrical optical components that enable mounting in the outside air are particularly advantageous (in contrast, in the case of spherical optical components, working in a vacuum atmosphere is required).

[0059] The optical system 17 includes, for example, two optical components, each optical component is positioned in a different plane, and these two planes are orthogonal to each other.

[0060] More precisely, the inclination angle of the wavefront at the image point B can be adjusted by the optical magnification of the optical system 17. In other words, the optical system 17 moves the time-compressed pulse from the object point A to the image point B, rotates the plane of the inclined wavefront of the time-compressed pulse, and arranges and overlaps it at the location required for the application. Between the object point A and the image point B, the optical pulse remains spatially dispersed, thereby avoiding the occurrence of undesirable effects during the propagation of the optical pulse between these two points.

[0061] Advantageously, the mirror 16 (or, as an alternative, a fourth diffraction grating) and the optical system 17 of the optical imaging system 15 can spatially and temporally overlap the components of the reflected optical pulse 160 at the image point B. In particular, at the image point B, the shaped optical pulse 150 is compressed, spatially and temporally recombined, and has an inclined emission wavefront. More precisely, the wavefronts 1501, 1502, 1503 overlap in the plane passing through the image point B. In the absence of other optical components (in particular, as described later, the diffraction grating 18), outside the image point B, these wavefronts 1501, 1502, 1503 are at the entrance of the optical imaging system 15, each propagation direction

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[0062] The shaped compressed optical pulse 150 with an inclined wavefront can be used for the target application at the image point B. In other words, the shaped compressed optical pulse 150 with an inclined wavefront can be used at the image point B away from the object point A without generating an undesirable nonlinear optical effect between the object point A and the image point B.

[0063] Figure 5 shows a second example of the compression system 5 according to the present invention. In this example, the optical imaging system further includes a final diffraction grating 18. This final diffraction grating 18 is positioned at the exit of the optical system 17 in the optical imaging system 15. This final diffraction grating 18 has the same dispersion degree as that of the aforementioned first diffraction grating 11, second diffraction grating 12, and third diffraction grating 13. The final diffraction grating 18 thus receives the shaped optical pulse 150 obtained at the exit of the other optical element 17.

[0064] More precisely, the final diffraction grating 18 is positioned at the aforementioned image point B, that is, at the place where the shaped optical pulse 150 is compressed, spatially and temporally recombined, and has an inclined emission wavefront. Advantageously, the final diffraction grating 18 is flat. The final diffraction grating 18 is inclined so that the plane of the final diffraction grating coincides with the plane of the inclined wavefront of the shaped compressed optical pulse 150.

[0065] This final diffraction grating 18 straightens different spectral components of the shaped optical pulse 150 so that they have the same propagation direction

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[0066] The shaped compressed optical pulse 180 with an inclined wavefront can be used at any point along the propagation direction from the image point B

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[0067] In the case of applications involving experiments carried out in vacuum or in a specific medium, for example a gas, only the final diffraction grating 18 is placed in the experimental chamber 30 filled with vacuum or a gaseous medium. However, the other optical components of the compression system 10 and the optical imaging system 15 can be placed outside the chamber 30. In fact, due to the angular dispersion of the compression pulse in front of the image point B, the risk of generating unwanted non-linear optical effects (for example in air) is limited. Furthermore, this configuration allows the size of the instrument, particularly the vacuum chamber 30, to be reduced and thus the associated costs to be cut. Furthermore, the integrity of the compressed optical pulse 180 with an inclined wavefront is improved because the optical path of the image B and the desired interaction region are shorter than those of prior art compression systems.

[0068] As an advantage, the compression and spatial shaping system according to the present invention can generate ultrashort, i.e., amplified optical pulses with a duration of 5 femtoseconds to 10 picoseconds, especially femtosecond pulses, by incorporating them into a chirped pulse amplifier instead of a conventional compressor. The compression system of the present disclosure can be used in particular in titanium-sapphire lasers, rare-earth-doped glass matrix lasers such as ytterbium-YAG lasers (Yb:YAG), neodymium-YAG lasers (Nd:YAG), thulium-YAG lasers (Tm-YAG), or erbium-YAG lasers (Er-HAG), or neodymium-doped yttrium lithium fluoride lasers (Nd:YLF), or fiber lasers.

[0069] The compression and spatial shaping system according to the present invention can also be combined with an optical parametric amplifier to generate variable wavelength radiation by sum frequency generation (i.e., SFG). In fact, in this case, the angular dispersion of the beam makes it easier to separate the different harmonics generated.

[0070] The compression and spatial shaping system can also be used for the generation of terahertz radiation by the interaction of a tilted wavefront time-compressed pulse with a nonlinear optical component.

[0071] The compression and spatial shaping system can also be advantageously used for inverse Compton scattering (or Thomson scattering), in which case the tilt of the wavefront allows for better overlap with the electron beam since the beams cross at a high angle of incidence.

[0072] The compression and spatial shaping system can also be used for dielectric laser acceleration (i.e., DLA).

[0073] The above-described compression and spatial shaping system 1 can perform the following method for the compression and spatial shaping of an optical pulse with a tilted wavefront.

[0074] According to the method according to the invention, the light source 2 generates an incident light pulse 100. This incident light pulse 100 has an upright incident wavefront with positive spectral dispersion.

[0075] This incident light pulse 100 propagates towards the compression system 5, more specifically towards the dispersive optical system 10 of the compression system 5

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[0076] Optionally, the method continues with the step of the dispersive optical system 10 receiving the incident light pulse 100. The dispersive optical system 10 then provides, as output, a temporally compressed light pulse 110 with an inclined wavefront at the object point A via a maximum of four consecutive diffractions of the incident light pulse 100. At the exit of the dispersive optical system 10, a compressed light pulse 110 with an inclined wavefront is formed at the object point A. In other words, the wavefronts 1101, 1102, 1103 associated with the compressed light pulse 110 are spatially and temporally superimposed at the object point A. More precisely, the wavefronts 1101, 1102, 1103 overlap spatially and temporally in a plane passing through the object point A. Furthermore, these wavefronts 1101, 1102, 1103 that spatially and temporally overlap at the object point A each have a different propagation direction

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[0077] The method then continues with the step in which the compressed optical pulse 110 is spatially shaped by the optical imaging system 15 and an image of the compressed optical pulse 110 having an inclined wavefront is formed at the image point B according to the desired tilt angle. The optical pulse obtained at the exit of the optical imaging system 15 is a spatially shaped time-compressed optical pulse 150 having an inclined wavefront at the image point B which is the image of the object point A. The optical imaging system enables the shaped time-compressed optical pulse 150 to be positioned so as to superimpose it at the desired image point B depending on the application. The tilt angle of the wavefront at the image point B depends in particular on the orientation of the deflection mirror 16 and / or the optical magnification of the optical system 17.

[0078] Optionally, the method diffracts the shaped compressed optical pulse 150 at the image point B on a diffraction grating arranged in the plane of the inclined wavefront of the shaped compressed optical pulse 150, so that the spectral components of the shaped compressed optical pulse 150

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Claims

1. A system (5) for compressing an optical pulse emitted by a light source (2), comprising a dispersive optical system (10) adapted to receive an incident optical pulse (100) having a plane wavefront of positive spectral dispersion incident perpendicularly, wherein the dispersive optical system (10) is designed to deliver a temporally compressed optical pulse (110) having an inclined wavefront at an object point (A), and the dispersive optical system (10) angularly disperses the propagation direction of the incident optical pulse through up to four diffractions according to the spectral dispersion of the incident optical pulse (100), and is designed to form the angularly dispersed temporally compressed optical pulse (110) having an inclined wavefront at the object point (A).

2. The dispersive optical system (10) includes three diffraction gratings (11, 12, 13) arranged in series on the incident optical pulse path (100), and each diffraction grating (11, 12, 13) of the dispersive optical system (10) is configured to angularly disperse the propagation direction of the incident optical pulse (100) according to the spectral dispersion of the incident optical pulse (100). The compression system (5) according to Claim 1.

3. Each of the three diffraction gratings (11, 12, 13) has a first degree of dispersion. The compression system according to Claim 2.

4. The dispersive optical system (10) includes a single diffraction grating and an optical element configured to angularly disperse the propagation direction of the incident optical pulse through up to three successive diffractions on the diffraction grating. The compression system (5) according to Claim 1.

5. The optical element includes a retroreflective prism or a mirror optical system. The compression system (5) according to Claim 4.

6. Including a mirror (16) disposed at or upstream of the object point (A), the mirror (16) being positioned to reflect the temporally compressed optical pulse (110) having the inclined wavefront. The compression system (5) according to any one of Claims 1 to 5.

7. Including another diffraction grating disposed at or upstream of the object point (A), the other diffraction grating being positioned to adjust the inclination angle of the wavefront of the temporally compressed optical pulse (110) having the inclined wavefront. The compression system (5) according to any one of Claims 1 to 5.

8. The other grating has a second degree of dispersion. The compression system (5) according to Claim 7. **Claim 9** The compression system (5) according to any one of claims 1 to 8, comprising an optical imaging system (15) configured to form an image of the temporally compressed optical pulse (110) having the tilted wavefront at an image point (B), and at this image point (B), to form a spatially shaped temporally compressed optical pulse (150) having a tilted wavefront corresponding to a predetermined tilt angle. **Claim 10** The compression system (5) according to claim 9, which depends on claim 3, wherein the optical imaging system (15) includes a final diffraction grating (18) disposed at the image point (B) in the plane of the tilted wavefront of the spatially shaped temporally compressed optical pulse (150) having an upright wavefront, and the final diffraction grating (18) has the first degree of dispersion. **Claim 11** A chirped pulse laser amplification system comprising an optical pulse source (2) and the compression system (5) according to any one of claims 1 to 10, wherein the source (2) includes an optical amplification system disposed upstream of the compression system (5). **Claim 12** An optical parametric amplification system comprising an optical parametric amplifier and the compression system (5) according to any one of claims 1 to 10, wherein the optical parametric amplifier is disposed upstream of the compression system (5). **Claim 13** - Receiving an incident optical pulse (100) having an upright incident wavefront with positive spectral dispersion; - Generating a temporally compressed optical pulse (110) having a tilted wavefront by a dispersive optical system (10), wherein the dispersive optical system (10) angularly disperses the propagation direction of the incident optical pulse (100) in accordance with the spectral dispersion of the incident optical pulse (100) through a maximum of four diffractions, and is designed to form the temporally compressed optical pulse (110) having a tilted wavefront and angular dispersion at an object point (A); A method for compressing an optical pulse emitted by a light source (2), comprising the above steps.

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