Grating compressor

Abstract

The invention relates to the technical field of high-power laser, and provides a grating compressor. The grating compressor comprises a first grating, a second grating and a reflector. The first grating has a first grating surface; the second grating has a second grating surface, an included angle is formed between the plane of the first grating surface and the plane of the second grating surface, and the first grating surface and the second grating surface are oppositely arranged; and the reflecting mirror is positioned on a light transmission path of the first grating and the second grating. Therefore, the light beam can be transmitted for multiple times among the first grating surface, the reflecting surface of the reflecting mirror and the second grating surface to realize compression of the pulse width, and compared with a traditional Treack type parallel grating pair compressor, the grating compressor is smaller in size and can meet the adaptation requirements of different types of laser systems.

Description

Technical Field

[0001] The invention relates to the technical field of high-power lasers, and in particular provides a grating compressor. Background Art

[0002] High-power ultrashort pulse lasers are widely used in high-energy-density physics, medical and industrial precision processing. In order to increase the output power of the laser, it is necessary to suppress the nonlinear effects in the laser amplification process and avoid damage to optical components. Chirped pulse amplification (CPA) and optical parametric chirped pulse amplification (OPCPA) technologies came into being. Before the pulse enters the laser amplifier, they first stretch the pulse to the picosecond or nanosecond level in the time domain; then, after the stretched pulse passes through the laser amplifier, the energy is greatly improved; finally, the high-energy pulse passes through the compressor, and the pulse width is compressed back to the picosecond, sub-picosecond or femtosecond level to obtain extremely high peak power. In a laser system that uses CPA or OPCPA technology, one of the key components is the pulse compressor, which directly affects the pulse width and beam quality of the final output of the laser.

[0003] The compressor in the laser system is usually composed of several gratings. By adjusting the distance between the grating pairs, the second-order dispersion can be effectively adjusted. However, the damage threshold of the grating is limited. When the incident light pulse width is 32fs and the central wavelength is 800nm, the damage threshold of the gold medium grating is about 0.4J / cm 2 When the incident light pulse width is 8.6ps and the central wavelength is 1053nm, the damage threshold of the multilayer dielectric grating is about 2.2J / cm 2 It can be seen that the higher the laser output energy, the larger the size of the compressor will be required to avoid damage to the compressor. In a picosecond petawatt laser system, the area occupied by the compressor can reach tens of square meters.

[0004] In order to reduce the size of the compressor, researchers have explored two ideas. One is to use a chirped volume Bragg grating (CVBG), which provides a large amount of dispersion while ensuring a small volume, but its damage threshold is also limited. When the laser pulse width is 3ns and the central wavelength is 1053nm, the damage threshold is about 10.3J / cm 2 . In addition, once a CVBG is prepared, the dispersion it provides cannot be flexibly adjusted. Another way to reduce the size of the compressor is to fold the optical path. For example, using two roof mirrors and a grating, a double-layer compressor that compresses pulses from picoseconds to femtoseconds can be constructed. This structure has the advantages of simple calibration, low cost and easy maintenance, but it is difficult to compress large-aperture laser beams due to the obstruction of various optical components. Summary of the invention

[0005] The purpose of the embodiments of the present application is to provide a compact grating compressor for use in a high-power laser system, aiming to solve the problems of existing grating compressors due to their large size, lack of flexibility and high cost.

[0006] To achieve the above purpose, the technical solution adopted in the embodiment of the present application is:

[0007] The embodiment of the present application provides a grating compressor for compressing a light beam output by a laser amplifier, comprising:

[0008] a first grating, the first grating having a first grating plane;

[0009] A second grating, wherein the second grating has a second grating plane, a plane where the first grating plane is located and a plane where the second grating plane is located form an angle, and the first grating plane and the second grating plane are arranged to face each other;

[0010] A reflector, wherein the reflector is located on the optical transmission path of the first grating and the second grating;

[0011] The incident light is diffracted by the first grating to form a first diffracted light, the first diffracted light is reflected between the reflector and the second grating to form a first reflected light, the first reflected light is diffracted by the second grating to form a second diffracted light, the second diffracted light is reflected again by the reflector, and the formed second reflected light is used as the incident light for the second-pass compression. The second reflected light is diffracted by the second grating to form a third diffracted light, the third diffracted light is reflected between the reflector and the first grating to form a third reflected light, the third reflected light is diffracted by the first grating, and is output from the compressor.

[0012] Beneficial effects of the embodiments of the present application: The grating compressor provided by the present application sets the grating planes of the two gratings facing each other, and the planes where the two grating planes are located are at an angle, and the reflector is set between the first grating and the second grating. In this way, the light beam can be compressed twice between the first grating plane, the reflective surface of the reflector and the second grating plane, and the grating compressor has a smaller volume and can meet the adaptation requirements of different types of laser systems.

[0013] In some embodiments, a plane where the first grating plane is located forms an angle with a plane where the second grating plane is located, and a reflecting surface of the reflector faces the first grating plane and the second grating plane.

[0014] In some embodiments, a reflective surface of the reflector faces toward the second grating surface, and in the first direction, the reflector is located between the first grating and the second grating.

[0015] In some embodiments, the first grating and the second grating are both reflective diffraction gratings, which may be dielectric film gratings, metal film gratings, or hybrid film gratings, etc. The grating constant of the first grating is the same as the grating constant of the second grating;

[0016] The reflector is a dielectric film reflector.

[0017] In some embodiments, the incident angle of the light beam on the first grating includes a horizontal incident angle and a vertical incident angle, the light beam is diffracted in the horizontal incident direction, and the light beam is reflected in the vertical incident direction.

[0018] In some embodiments, a minimum increased height of the light beam in the third direction is greater than a projection height of the light beam in the third direction.

[0019] In some embodiments, in the first direction, a distance between the position of the first diffracted light to the reflector and the incident light is greater than zero. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 A top view of a grating compressor provided by an embodiment of the present invention;

[0022] Figure 2 A front view of a grating compressor provided by an embodiment of the present invention;

[0023] Figure 3 A top view of an equivalent optical path of a grating compressor provided by an embodiment of the present invention;

[0024] Figure 4 A front view of the equivalent optical path of the grating compressor provided by an embodiment of the present invention.

[0025] Among them, the figure marks in the figure are: 1. first grating; 1a. first grating plane; 2. second grating; 2a. second grating plane; 3. reflector; 4. incident light beam; 5. first diffracted light; 6. first reflected light; 7. second diffracted light; 8. second reflected light; 9. third diffracted light; 10. third reflected light; 11. outgoing light beam; first direction y; second direction x; third direction z. DETAILED DESCRIPTION

[0026] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0027] In the description of the present invention, it is necessary to understand that the terms "length", "width", "height", "vertical", "horizontal", "inside", "outside", etc. indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0028] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0029] Please refer to Figure 1 and Figure 3 An embodiment of the present application provides a compact grating compressor for compressing a light beam 4 output by a laser amplifier, comprising a first grating 1, a second grating 2 and a reflector 3.

[0030] The first grating 1 has a first grating surface 1a;

[0031] The second grating 2 has a second grating plane 2a, the plane where the first grating plane 1a is located and the plane where the second grating plane 2a is located form an angle, and the first grating plane 1a and the second grating plane 2a are arranged facing each other;

[0032] The reflector is located on the optical transmission path of the first grating 1 and the second grating 2;

[0033] The incident light 4 is diffracted by the first grating 1 to form the first diffracted light 5, the first diffracted light 5 is reflected between the reflector 3 and the second grating 2 to form the first reflected light 6, the first reflected light 6 is diffracted by the second grating 2 to form the second diffracted light 7, the second diffracted light 7 is reflected again by the reflector 3, and the formed second reflected light 8 is used as the incident light of the second-pass compression. The second reflected light 8 is diffracted by the second grating 2 to form the third diffracted light 9, the third diffracted light 9 is reflected between the reflector 3 and the first grating 1 to form the third reflected light 10, the third reflected light 10 is diffracted by the first grating 1, and the light beam 11 is output from the compressor.

[0034] It can be understood that a grating is an optical device composed of a large number of parallel slits of equal width and equal spacing. Then, the grating plane is the surface of the grating on which the above parallel slits are arranged.

[0035] The first grating plane 1a and the second grating plane 2a are arranged opposite to each other, which means that the grating planes of the two gratings are arranged opposite to each other, so that the light beam 4 can be transmitted multiple times between the two grating planes. At the same time, the first grating plane 1a and the second grating plane 2a are arranged at an angle, which means that the planes where the two planes are located are at an angle, that is, it can be an acute angle, a right angle or an obtuse angle.

[0036] The reflector 3 is arranged on the optical transmission path of the first grating 1 and the second grating 2 , which means that the light beam 4 can be transmitted between the reflector and the first grating 1 , or the light beam 4 can also be transmitted between the reflector and the second grating 2 .

[0037] Specifically, the light beam 4 emitted by the laser amplifier is the initial light beam 4, that is, the uncompressed light beam 4, which is first diffracted and reflected by the first grating plane 1a of the first grating 1. After diffraction by the first grating plane 1a, a first diffracted light 5 is formed. The first diffracted light 5 can be diffracted and reflected multiple times between the second grating plane 2a and the reflecting surface of the reflector 3 (6, 7, 8, 9). After the third reflected light 10 is diffracted by the grating 1, compression is completed and an output light beam 11 is emitted.

[0038] The compact grating compressor provided by the present application sets the grating planes of the two gratings facing each other, and the planes where the two grating planes are located are at an angle, so that in a certain direction, the projection of the first grating 1 and the projection of the second grating 2 can overlap. The reflector is set between the first grating 1 and the second grating 2, so that the light beam 4 can be compressed multiple times between the first grating plane 1a, the reflection surface of the reflector 3 and the second grating plane 2a, and the overall volume of the grating compressor is smaller, which can meet the adaptation requirements of different types of laser systems.

[0039] For example, Figure 2 As shown in the figure, in the direction perpendicular to the paper surface, the projection of the first grating 1 and the projection of the second grating 2 partially overlap. It can be understood that the length of the grating compressor along the second direction x can be reduced. At the same time, Figure 1 As shown in the figure, in the direction perpendicular to the paper, the plane where the first grating plane 1a is located and the plane where the second grating plane 2a is located form an acute angle. It can be understood that the width of the grating compressor along the first direction y can be reduced. In summary, the volume of the grating compressor can be developed towards miniaturization.

[0040] Specifically, Figure 1As shown, in some embodiments, the plane where the first grating plane 1a is located forms an acute angle with the plane where the second grating plane 2a is located, the reflecting surface of the reflector 3 faces the first grating plane 1a and the second grating plane 2a, and, in the first direction y, the projection of the first grating 1 partially overlaps with the projection of the second grating 2.

[0041] It can be understood that the first direction y is the width direction of the grating compressor, the second direction x is the length direction of the grating compressor, and the third direction z is the height direction of the grating compressor. The first direction y, the second direction x and the third direction z are perpendicular to each other.

[0042] The reflecting surface of the reflecting mirror 3 faces the first grating surface 1a and the second grating surface 2a, so that the optical path is folded three times according to actual use conditions, so that the overall length of the grating compressor is further reduced.

[0043] Figure 1 and Figure 2 Please refer to the equivalent optical path diagram Figure 3 and Figure 4 The reflector here only plays the role of "making the laser enter the compressor twice".

[0044] Please refer to Figure 3 and Figure 4 In some embodiments, the reflective surface of the reflector faces the second grating plane 2a, and the reflector is located between the first grating 1 and the second grating 2 in the first direction y.

[0045] It can be understood that the first direction y is the width direction of the grating compressor, the second direction x is the length direction of the grating compressor, and the third direction z is the height direction of the grating compressor. The first direction y, the second direction x and the third direction z are perpendicular to each other.

[0046] Optionally, the angle between the plane where the first grating plane 1a is located and the plane where the second grating plane 2a is located is zero, that is, the two grating planes are arranged in parallel.

[0047] In some embodiments, the first grating 1 and the second grating 2 are both reflective diffraction gratings, and the grating constant of the first grating 1 is the same as the grating constant of the second grating 2;

[0048] The reflector is a dielectric film reflector.

[0049] It can be understood that the grating can cause the light beam to diffract or reflect when passing through, thereby achieving adjustment and control of the light beam 4.

[0050] Dielectric film reflectors are reflectors that use the principles of reflection and refraction of dielectric films to achieve higher reflectivity for light within a specific wavelength range. Usually, dielectric film reflectors are composed of a substrate material and a dielectric film covering its surface. By precisely controlling the thickness and refractive index of the dielectric film, selective increase or suppression of light of a specific wavelength can be achieved.

[0051] Please refer to Figures 1 to 4 In some embodiments, the incident angle of the light beam 4 on the first grating 1 includes a horizontal incident angle and a vertical incident angle, the light beam 4 is diffracted in the horizontal incident direction, and the light beam 4 is reflected in the vertical incident direction.

[0052] It can be understood that the incident angle of the light beam 4 emitted by the laser amplifier on the first grating plane 1 a has two components, including a horizontal incident angle and a vertical incident angle.

[0053] The horizontal incident angle is the incident angle formed by the light beam 4 in the plane where the first direction y and the second direction x are located and the first grating surface 1a; the vertical incident angle is the incident angle formed by the light beam 4 in the plane where the second direction x and the third direction z are located and the first grating surface 1a.

[0054] Specifically, as shown in the figure, the plane where the first direction y and the second direction x are located is a plane perpendicular to the grating lines on the grating surface, and as shown in the figure, the plane where the second direction x and the third direction z are located is a plane parallel to the grating lines on the grating surface. At the same time, the horizontal incident angle is recorded as γ, and the vertical incident angle is recorded as Γ. At the same time, in the plane where the first direction y and the second direction x are located, the light beam 4 is diffracted on the first grating surface 1a, and in the plane where the second direction x and the third direction z are located, the light beam 4 is only reflected on the first grating surface 1a.

[0055] The total phase shift of the grating compressor provided by this application is:

[0056]

[0057] Where ω is the angular frequency and G is Figure 3 and Figure 4 The vertical distance between the first grating 1 and the second grating 2 in the equation, θ is the angle between the horizontal incident angle and the diffraction angle, c is the speed of light, and d is the grating constant. The first term on the right side of the equal sign in the equation represents the phase generated by the optical path, and the second term represents the phase generated by the grating diffraction.

[0058] The group delay dispersion is the second-order derivative of the total phase shift, and the grating compressor of the present application compresses the incident light twice, so the group delay dispersion of the grating compressor is obtained by the following formula:

[0059]

[0060] Where λ is the wavelength of the incident light. In this embodiment, the incident light is a circular Gaussian spot with a diameter of 20 mm, a central wavelength of 1053 nm, a spectrum width of 18 nm, a pulse width of 2 ns, and a grating constant of 1 / 1740 mm. If the incident light is compressed to 100 fs, the second-order dispersion that needs to be compensated by the grating compressor is -6.54×10 7 fs 2 .

[0061] Optionally, in a specific embodiment, the horizontal incident angle is 70.4°, the vertical incident angle is 0.3°, and the total volume of the grating compressor is about 4485.713 cm 3 , which is two-thirds of the conventional compressor structure.

[0062] In some embodiments, the minimum increased height of the incident light beam 4 in the third direction z is greater than the projection height of the incident light beam 4 in the third direction z.

[0063] It can be understood that the minimum increased height of the incident light beam 4 in the third direction z is greater than the projection height of the incident light beam 4 in the third direction z, so that the outgoing light beam 11 can be separated from the incident light beam 4.

[0064] In some embodiments, in the first direction y, the distance between the position of the first diffracted light 5 to the reflector and the light beam 4 is greater than zero.

[0065] It can be understood that the distance between the position of the first diffracted light 5 to the reflector and the light beam 4 is greater than zero, so that the first diffracted light 5 can be separated from the incident light beam 4.

[0066] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A grating compressor for compressing a light beam emitted by a laser amplifier, the characteristics of which include: a first grating having a first grating plane; A second grating, wherein the second grating has a second grating plane, a plane where the first grating plane is located and a plane where the second grating plane is located form an angle, and the first grating plane and the second grating plane are arranged to face each other; A reflector, wherein the reflector is located on the optical transmission path of the first grating and the second grating; The incident light is diffracted by the first grating to form a first diffracted light, the first diffracted light is reflected between the reflector and the second grating to form a first reflected light, the first reflected light is diffracted by the second grating to form a second diffracted light, the second diffracted light is reflected again by the reflector, and the formed second reflected light is used as the incident light for the second pass compression; The second reflected light is diffracted by the second grating to form a third diffracted light, the third diffracted light is reflected between the reflector and the first grating to form a third reflected light, and the third reflected light is diffracted by the first grating and output from the compressor.

2. The grating compressor according to claim 1, characterized in that: The plane where the first grating surface is located forms an angle with the plane where the second grating surface is located, and the reflection surface of the reflection mirror faces the first grating surface and the second grating surface.

3. The grating compressor according to claim 1, characterized in that: In a first direction, the reflector is located between the first grating and the second grating.

4. The grating compressor according to claim 1, characterized in that: The first grating and the second grating are both reflective diffraction gratings, and the grating constant of the first grating is the same as the grating constant of the second grating; The reflector is a dielectric film reflector.

5. The grating compressor according to claim 1, characterized in that: The incident angle of the light beam on the first grating includes a horizontal incident angle and a vertical incident angle. The light beam is diffracted in the horizontal incident direction, and the light beam is reflected in the vertical incident direction.

6. The grating compressor according to claim 1, characterized in that: The minimum increased height of the light beam in the third direction is greater than the projection height of the light beam in the third direction.

7. The grating compressor according to claim 1, characterized in that: In the first direction, a distance between the position of the first diffracted light to the reflector and the incident light is greater than zero.

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