A grating compressor

Abstract

The present application relates to the field of high-power laser technology, and provides a grating compressor.The grating compressor comprises a first grating, a second grating and a mirror; the first grating has a first grating surface; the second grating has a second grating surface, the plane in which the first grating surface lies and the plane in which the second grating surface lies form an angle, and the first grating surface and the second grating surface are oppositely arranged; and the mirror is located on the light path transmission path of the first grating and the second grating.In this way, the light beam can be transmitted between the first grating surface, the reflecting surface of the mirror and the second grating surface for multiple times to compress the pulse width, and compared with the traditional Treacy 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] This invention relates to the field of high-power laser technology, and in particular to a grating compressor. Background Technology

[0002] High-power ultrashort pulse lasers are widely used in high-energy-density physics, medicine, and precision industrial machining. To improve the output power of lasers, it is essential to suppress nonlinear effects during laser amplification and avoid damage to optical components. Chirped pulse amplification (CPA) and optical parametric chirped pulse amplification (OPCPA) technologies have emerged to address this need. Before the pulse enters the laser amplifier, it is first broadened to the picosecond or nanosecond level in the time domain. Then, the broadened pulse passes through the laser amplifier, resulting in a significant energy boost. Finally, the high-energy pulse passes through a compressor, compressing the pulse width back to the picosecond, sub-picosecond, or femtosecond level to achieve extremely high peak power. In laser systems employing CPA or OPCPA technology, one of the key components is the pulse compressor, which directly affects the final output pulse width and beam quality of the laser.

[0003] The compressor in a laser system typically consists of several gratings. By adjusting the distance between the grating pairs, the second-order dispersion can be effectively controlled. However, the damage threshold of the gratings is limited. With an incident light pulse width of 32 fs and a center wavelength of 800 nm, the damage threshold of a gold dielectric grating is approximately 0.4 J / cm². 2 When the incident light pulse width is 8.6 ps and the center wavelength is 1053 nm, the damage threshold of the multilayer dielectric grating is approximately 2.2 J / cm. 2 This shows that the higher the laser output energy, the larger the required compressor size will be to avoid damage. In picosecond-level petawatt laser systems, the compressor can occupy an area of ​​tens of square meters.

[0004] To reduce the size of the compressor, researchers have explored two approaches. One is to use a chirped volume Bragg grating (CVBG), which provides a large dispersion while maintaining a small size, but its damage threshold is also limited. With a laser pulse width of 3 ns and a center wavelength of 1053 nm, the damage threshold is approximately 10.3 J / cm². 2 Furthermore, once a CVBG is fabricated, the dispersion it provides cannot be flexibly adjusted. Another way to reduce the compressor size is to fold the optical path, for example, by using two roof mirrors and a grating, which can create a two-layer compressor that can compress pulses from picoseconds to femtoseconds. This structure has advantages such as simple calibration, low cost, and convenient 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 this application is to provide a compact grating compressor for high-power laser systems, aiming to solve the problems of existing grating compressors being large in size, lacking flexibility, and having high cost.

[0006] To achieve the above objectives, the technical solution adopted in the embodiments of this application is as follows:

[0007] This application provides a grating compressor for compressing the beam output from a laser amplifier, comprising:

[0008] A first grating, the first grating having a first grating surface;

[0009] The second grating has a second grating surface, the plane containing the first grating surface forms an angle with the plane containing the second grating surface, and the first grating surface and the second grating surface are arranged facing each other;

[0010] A 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 first diffracted light. This first diffracted light is reflected between the mirror and the second grating to form first reflected light. The first reflected light is then diffracted by the second grating to form second diffracted light. This second diffracted light is reflected again by the mirror, forming second reflected light, which serves as the second-stage compressed incident light. The second reflected light is diffracted by the second grating to form third diffracted light. This third diffracted light is reflected between the mirror and the first grating to form third reflected light. This third reflected light is then diffracted by the first grating and output from the compressor.

[0012] The beneficial effects of the embodiments of this application are as follows: The grating compressor provided in this application has two gratings with their grating surfaces facing each other and the planes containing the two grating surfaces forming an angle. A reflector is placed between the first grating and the second grating. In this way, the light beam can be compressed twice between the first grating surface, the reflecting surface of the reflector, and the second grating surface. Furthermore, the grating compressor has a smaller volume and can meet the adaptation requirements of different types of laser systems.

[0013] In some embodiments, the plane containing the first grating surface forms an angle with the plane containing the second grating surface, and the reflecting surface of the mirror faces the first grating surface and the second grating surface.

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

[0015] In some embodiments, both the first grating and the second grating are reflection diffraction gratings, which can be dielectric film gratings, metal film gratings, or hybrid film gratings, etc. The grating constant of the first grating is the same as that 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, the minimum increase in height of the beam in a third direction is greater than the projection height of the beam in a third direction.

[0019] In some embodiments, in a first direction, the distance between the position of the first diffracted light to the mirror and the incident light is greater than zero. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

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

[0022] Figure 2 This is a front view of a grating compressor provided in an embodiment of the present invention;

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

[0024] Figure 4 This is a front view of the equivalent optical path of the grating compressor provided in an embodiment of the present invention.

[0025] In the figure, the reference numerals are as follows: 1. First grating; 1a. First grating surface; 2. Second grating; 2a. Second grating surface; 3. Reflector; 4. Incident beam; 5. First diffracted beam; 6. First reflected beam; 7. Second diffracted beam; 8. Second reflected beam; 9. Third diffracted beam; 10. Third reflected beam; 11. Outgoing beam; First direction y; Second direction x; Third direction z. Detailed Implementation

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

[0027] In the description of this invention, it should be understood that the terms "length", "width", "height", "vertical", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0028] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "multiple" means two or more, unless otherwise explicitly specified.

[0029] Please refer to Figure 1 and Figure 3 This application provides a compact grating compressor for compressing the beam 4 output by a laser amplifier, including 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 surface 2a, the plane containing the first grating surface 1a forms an angle with the plane containing the second grating surface 2a, and the first grating surface 1a and the second grating surface 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 mirror 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 mirror 3 to form the second reflected light 8, which serves as the second-stage compressed incident light. 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 mirror 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 output as beam 11 from the compressor.

[0034] Understandably, a grating is an optical device composed of a large number of parallel slits of equal width and spacing. Therefore, the grating surface is the surface on the grating where the aforementioned parallel slits are arranged.

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

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

[0037] Specifically, the beam 4 emitted by the laser amplifier is the initial beam 4, that is, the uncompressed beam 4. It first diffracts and reflects with the first grating surface 1a of the first grating 1. After diffraction by the first grating surface 1a, it forms the first diffracted light 5. The first diffracted light 5 can undergo multiple diffractions and reflections (6, 7, 8, 9) between the second grating surface 2a and the reflecting surface of the mirror 3. The third reflected light 10 is compressed after diffraction by the grating 1 and outputs the beam 11.

[0038] The compact grating compressor provided in this application arranges two gratings with their grating surfaces facing each other, and the planes containing the two grating surfaces are at an angle. Therefore, in a certain direction, the projection of the first grating 1 and the projection of the second grating 2 can overlap. A reflector is positioned between the first grating 1 and the second grating 2. Thus, the beam 4 can be compressed multiple times between the first grating surface 1a, the reflecting surface of the reflector 3, and the second grating surface 2a. Furthermore, the overall size of this grating compressor is smaller, meeting the adaptation requirements of different types of laser systems.

[0039] For example, such as Figure 2 As shown, in the direction perpendicular to the paper, the projections of the first grating 1 and the second grating 2 partially overlap. Understandably, the length of the grating compressor along the second direction x can be reduced. Meanwhile, as... Figure 1 As shown, in the direction perpendicular to the paper, the plane containing the first grating surface 1a forms an acute angle with the plane containing the second grating surface 2a. Understandably, the width of the grating compressor along the first direction y can be reduced. In summary, the size of this grating compressor can be miniaturized.

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

[0041] Understandably, 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 all perpendicular to each other.

[0042] The reflecting surface of the reflector 3 faces the first grating surface 1a and the second grating surface 2a, thereby folding the optical path three times according to the actual use, which further reduces the overall length of the grating compressor.

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

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

[0045] Understandably, the first direction y can be 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 all perpendicular to each other.

[0046] Optionally, the angle between the plane containing the first grating surface 1a and the plane containing the second grating surface 2a is zero, that is, the two grating surfaces 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 that of the second grating 2;

[0048] The reflector is a dielectric film reflector.

[0049] Understandably, the grating can cause the light beam to diffract or reflect as it passes through, thereby enabling the adjustment and control of the light beam 4.

[0050] Dielectric mirrors utilize the principles of reflection and refraction of dielectric films to achieve high reflectivity for light within a specific wavelength range. Typically, dielectric mirrors consist of a substrate material and a dielectric film covering its surface. By precisely controlling the thickness and refractive index of the dielectric film, selective enhancement or suppression of specific wavelengths of light 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 diffracts in the horizontal incident direction and is reflected in the vertical incident direction.

[0052] Understandably, the incident angle of the light beam 4 emitted by the laser amplifier on the first grating surface 1a has two components, including the horizontal incident angle and the vertical incident angle.

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

[0054] Specifically, as shown in the figure, the plane containing the first direction y and the second direction x is a plane perpendicular to the grating lines on the grating surface. Similarly, the plane containing the second direction x and the third direction z is a plane parallel to the grating lines on the grating surface. The horizontal angle of incidence is denoted as γ, and the vertical angle of incidence is denoted as Γ. Furthermore, within the plane containing the first direction y and the second direction x, beam 4 diffracts on the first grating surface 1a, while within the plane containing the second direction x and the third direction z, beam 4 is only reflected on the first grating surface 1a.

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

[0056]

[0057] In the formula, 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 is given by θ, where 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-hand side of the equation represents the phase generated by the optical path length, and the second term represents the phase generated by grating diffraction.

[0058] The group delay dispersion is the second derivative of the total phase shift. Since the grating compressor in this application compresses the incident light twice, the group delay dispersion of the grating compressor is derived from the following equation:

[0059]

[0060] In the formula, λ represents the incident light wavelength. In this embodiment, the incident light is a circular Gaussian spot with a diameter of 20 mm, a center wavelength of 1053 nm, a spectral width of 18 nm, a pulse width of 2 ns, and a grating constant of 1 / 1740 mm. To compress the incident light to 100 fs, the second-order dispersion compensation required by the grating compressor is -6.54 × 10⁻⁶. 7 fs 2 .

[0061] Optionally, in one 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 approximately 4485.713 cm³. 3 It is two-thirds the size of a conventional compressor structure.

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

[0063] Understandably, the minimum increase in height of the incident beam 4 in the third direction z is greater than the projection height of the incident beam 4 in the third direction z, which allows the outgoing beam 11 to separate from the incident beam 4.

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

[0065] Understandably, the distance between the position of the first diffracted light 5 and the mirror and the beam 4 is greater than zero, which can separate the first diffracted light 5 from the incident beam 4.

[0066] The above are merely 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 within the protection scope of the present invention.

Claims

1. A grating compressor for compressing a light beam emitted from a laser amplifier, characterized by: A first grating, the first grating having a first grating surface; The second grating has a second grating surface, and both the first grating and the second grating are reflection diffraction gratings; the plane containing the first grating surface forms an angle with the plane containing the second grating surface, and the first grating surface and the second grating surface are arranged facing each other; A reflector is located on the optical transmission path of the first grating and the second grating; in a first direction, the reflector is disposed between 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 mirror 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 mirror, and the second reflected light is used as the second-stage compressed incident light. The second reflected light is diffracted by the second grating to form a third diffracted light. The third diffracted light is reflected between the mirror and the first grating to form a third reflected light. The third reflected light is diffracted by the first grating and output from the compressor. The first diffracted light is first reflected by the mirror and then diffracted at the second grating. The third diffracted light is first reflected by the mirror and then diffracted at the first grating.

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

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

4. 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 diffracts in the horizontal incident direction and is reflected in the vertical incident direction.

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

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

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