Low order aberration compensation structure, double pass active mirror amplifier and laser

Abstract

The application provides a low-order aberration compensation structure, a double-pass active mirror amplifier and a laser. The low-order aberration compensation structure comprises: a first polarization beamsplitter, which can transmit laser of a first polarization direction and reflect laser of a second polarization direction; a wavefront adjustment structure, which can receive the laser of the first polarization direction and change the polarization direction of the laser from the first polarization direction to the second polarization direction through reflection; and a landing point adjustment structure, which is used for receiving the laser of the second polarization direction and reflecting the landing point of the laser of the second polarization direction to the first polarization beamsplitter, so that the landing point area of the laser of the second polarization direction on the first polarization beamsplitter coincides with the transmission area of the laser of the first polarization direction on the first polarization beamsplitter. The technical scheme of the application can solve the problems of complex structure and high cost of the low-order aberration compensation structure in the related art.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of laser amplification, and in particular to a low-order aberration compensation structure, a double-pass active mirror amplifier and a laser. BACKGROUND

[0002] An active mirror is a device that uses stimulated radiation of light to amplify the energy (power) of light. By using an active mirror, high laser energy or power can be obtained while maintaining the quality of the laser (including pulse width, line width, polarization characteristics, etc.).

[0003] The active mirror is a reflective device, and after the laser passes through the active mirror, low-order aberrations are generated, mainly manifested as defocus and astigmatism. The cause of the defocus phenomenon is mainly due to the temperature difference between the upper and lower surfaces of the gain medium of the active mirror, and the reflection of the laser through the gain medium causes the defocus of the laser. The cause of the astigmatism phenomenon is derived from the aspect ratio of the gain medium not being 1 and the oblique incidence of the laser leading to asymmetry in the horizontal and vertical directions of the laser.

[0004] In related technologies, a deformable mirror is generally used to compensate for the low-order aberration of the laser. The overall stroke of the deformable mirror is usually short, and the adjustable low-order aberration is in the order of tens of microns. The effect is not good for a larger low-order aberration of hundreds of microns, and the cost is high, and a feedback control system is needed. The use of a lens group requires a large number of lenses and dynamic changes in position, which is complex to adjust. SUMMARY

[0005] The present application provides a low-order aberration compensation structure, a double-pass active mirror amplifier and a laser to solve the problems of complex structure and high cost of the low-order aberration compensation structure in related technologies.

[0006] In one aspect, the present application provides a low-order aberration compensation structure, comprising: a first polarization beamsplitter capable of transmitting laser of a first polarization direction and reflecting laser of a second polarization direction; a wavefront adjustment structure configured to receive the laser of the first polarization direction and change the polarization direction of the laser from the first polarization direction to the second polarization direction through reflection; and a landing point adjustment structure configured to receive the laser of the second polarization direction and reflect the landing point of the laser of the second polarization direction onto the first polarization beamsplitter, so that the landing point area of the laser of the second polarization direction on the first polarization beamsplitter coincides with the transmission area of the laser of the first polarization direction on the first polarization beamsplitter.

[0007] In some embodiments, the first polarization direction is a horizontal direction, and the second polarization direction is a vertical direction.

[0008] In some embodiments, the wavefront adjustment structure comprises a first mirror and a second mirror, the laser of the first polarization direction transmitted from the first polarizing beam splitter passes through the first mirror and the second mirror in sequence, and the polarization direction of the laser reflected from the second mirror is changed from the first polarization direction to the second polarization direction.

[0009] In some embodiments, the landing point adjustment structure comprises a third mirror and a fourth mirror, the laser of the second polarization direction passes through the third mirror and the fourth mirror in sequence, and the landing point area of the laser reflected from the fourth mirror is located on the first polarizing beam splitter and coincides with the transmission area of the laser of the first polarization direction on the first polarizing beam splitter.

[0010] In some embodiments, the low-order aberration compensation structure of the laser further comprises: a focal length adjustment structure arranged on the optical path of the laser.

[0011] In some embodiments, the focal length adjustment structure comprises a spherical lens.

[0012] In some embodiments, the focal length adjustment structure is arranged between the landing point adjustment structure and the first polarizing beam splitter.

[0013] In another aspect, the present application also provides a double-pass active mirror amplifier, comprising: an active mirror configured to receive laser of a first polarization direction; and a low-order aberration compensation structure arranged at a rear end of the active mirror, the low-order aberration compensation structure being the low-order aberration compensation structure described above, the low-order aberration compensation structure being configured to receive the laser of the first polarization direction transmitted from the active mirror and reflect laser of a second polarization direction to the active mirror.

[0014] In some embodiments, the double-pass active mirror amplifier further comprises: a second polarizing beam splitter arranged upstream of the active mirror, the second polarizing beam splitter being capable of transmitting the laser of the first polarization direction and reflecting the laser of the second polarization direction.

[0015] In another aspect, the present application also provides a laser, comprising: a double-pass active mirror amplifier, the double-pass active mirror amplifier being the double-pass active mirror amplifier described above.

[0016] The low-order aberration compensation structure provided by the application can be arranged at the rear end of the active mirror. The laser of the first polarization direction first passes through the active mirror, and low-order aberration is generated, forming laser with the first aberration and the polarization direction being the first polarization direction. After the laser enters the low-order aberration compensation structure, it first transmits through the first polarization beamsplitter, forms a transmission point on the wave surface adjusting structure, and then is reflected by the wave surface adjusting structure. The wave surface and the polarization direction of the laser emitted from the wave surface adjusting structure are changed, and the laser becomes laser with the first aberration and the polarization direction being the second polarization direction. The laser enters the landing point adjusting structure, and the landing point adjusting structure can reflect the landing point of the laser to the first polarization beamsplitter, and make the landing point area of the laser coincide with the transmission area of the laser. Finally, the laser emitted from the low-order aberration compensation structure has a rotating wave surface compared with the incident laser, the polarization direction changes from the first polarization direction to the second polarization direction, the emission direction is opposite to the incident direction of the laser, the aberration condition is the same as that of the incident laser, and the laser still has the first aberration. The above laser can enter the active mirror again along the direction opposite to the incident laser, and generate the second aberration after passing through the active mirror. The second aberration can offset the first aberration, so that the astigmatism phenomenon of the laser emitted from the active mirror is compensated. The low-order aberration compensation structure has low cost, simple structure and convenient processing. BRIEF DESCRIPTION OF DRAWINGS

[0017] The accompanying drawings, which are incorporated into and form a part of the specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the application.

[0018] Figure 1 A perspective view of the low-order aberration compensation structure provided by the embodiment of the application is shown.

[0019] Figure 2 A structure diagram of the double-pass active mirror amplifier is shown, wherein Figure 2 The laser incident light path of the laser double-pass laser active mirror is shown.

[0020] Figure 3 A structure diagram of the double-pass active mirror amplifier is shown, wherein Figure 3 The laser emission light path of the laser double-pass laser active mirror is shown.

[0021] Figure 4 A structure diagram of the double-pass active mirror amplifier is shown, wherein Figure 4 The laser incident light path and the laser emission light path of the laser double-pass laser active mirror are shown.

[0022] BRIEF DESCRIPTION OF DRAWINGS

[0023] 1-laser incident light path; 2-laser emission light path;

[0024] 10 - first polarization beamsplitter;

[0025] 20 - wavefront adjustment structure; 21 - first mirror; 22 - second mirror;

[0026] 30 - spot adjustment structure; 31 - third mirror; 32 - fourth mirror;

[0027] 40 - focal length adjustment structure;

[0028] 50 - low-order aberration compensation structure;

[0029] 60 - activation mirror;

[0030] 70 - second polarization beamsplitter;

[0031] 80 - double-pass activation mirror amplifier.

[0032] The specific embodiments of the present application have been shown and described in the above-described drawings and text by way of illustration. The drawings and description are not intended to limit the scope of the present application in any manner. Various modifications and alterations to this concept will become apparent to those skilled in the art from the text and drawings. DETAILED DESCRIPTION

[0033] The embodiments of the present application will be described in detail below with reference to the drawings, in which the same or similar components have the same or similar reference numerals throughout. The embodiments described below are examples for explaining the present application and are not intended to limit the scope of the present application.

[0034] In the description of the present application, it should be understood that the terms "center", "vertical", "longitudinal", "width", "upper", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only used to facilitate the description of the present application and simplify the description, and therefore cannot be understood as indicating or implying that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0035] In addition, the terms "first", "second", etc. are used only for descriptive purposes and do not connote or imply a relative importance or an ordering between or among the indicated features. Accordingly, a feature defined with "first" or "second" can include at least one of the features. In this application, unless specifically stated and limited otherwise, the terms "mount", "fasten", "connect", "attach", and the like, are used broadly and encompass both direct and indirect mounting, fastening, connecting, and attaching, as well as fixed and removable mounting, fastening, connecting, and attaching, and can include mechanical connection, electrical connection, or communication that is non-mechanical, unless otherwise specifically stated and limited. The terms "mount", "fasten", "connect", "attach", and the like, are to be interpreted broadly to include any connection, coupling, fastening, or attachment between or among two or more elements, whether direct or indirect.

[0036] In this application, unless specifically stated and limited otherwise, a first feature "on", "above", or "under" a second feature can be directly in contact with the second feature, or indirectly in contact with the second feature through an intermediate medium. Also, a first feature "over", "above", or "on" a second feature can be directly above or obliquely above the second feature, or can only indicate that the first feature is at a higher level than the second feature. A first feature "under", "below", or "underneath" a second feature can be directly below or obliquely below the second feature, or can only indicate that the first feature is at a lower level than the second feature.

[0037] In the description of the specification, the description of the terms "optionally", "optional implementation" and the like means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In the specification, the illustrative description of the above terms is not necessarily directed to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any suitable manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine different embodiments or examples described in the specification and the features of different embodiments or examples, without contradiction.

[0038] In the related art, the activation mirror is a reflective device, and after the laser passes through the activation mirror, low-order aberrations are generated, mainly manifested as defocus and astigmatism. Among them, the cause of the defocus phenomenon is mainly due to the temperature difference between the upper and lower surfaces of the gain medium of the activation mirror, and the reflection of the laser after passing through the gain medium will cause the defocus of the laser. The cause of the astigmatism phenomenon is derived from the aspect ratio of the gain medium not being 1 and the oblique incidence of the laser causing the asymmetry of the laser in the horizontal and vertical directions.

[0039] At present, the low-order aberration of the laser is generally compensated by a deformable mirror. The overall stroke of the deformable mirror is usually short, and the adjustable low-order aberration is in the order of tens of microns. The effect is not good for a larger low-order aberration of hundreds of microns, and the cost is high. A feedback control system is needed, which is complex. If a lens group is used, a large number of lenses are needed, and the position needs to be dynamically changed, which is complex to adjust.

[0040] The application provides a low-order aberration compensation structure to solve the problems of complex structure and high cost of the low-order aberration compensation structure in the related art.

[0041] Figure 1 A perspective view of a low-order aberration compensation structure provided by an embodiment of the application.

[0042] As shown in Figure 1 and Figure 2 , the low-order aberration compensation structure of the embodiment includes a first polarization beamsplitter 10, a wavefront adjustment structure 20, and a landing point adjustment structure 30.

[0043] The first polarization beamsplitter 10 can transmit laser of a first polarization direction and reflect laser of a second polarization direction.

[0044] The wavefront adjustment structure 20 is configured to receive the laser of the first polarization direction and change the polarization direction of the laser from the first polarization direction to the second polarization direction through reflection.

[0045] The landing point adjustment structure 30 is configured to receive the laser of the second polarization direction and reflect the landing point of the laser of the second polarization direction to the first polarization beamsplitter 10, so that the landing point area of the laser of the second polarization direction on the first polarization beamsplitter 10 coincides with the transmission area of the laser of the first polarization direction on the first polarization beamsplitter 10.

[0046] By applying the technical solution of the embodiment, the low-order aberration compensation structure 50 can be arranged at the rear end of the active mirror 60. After the laser of the first polarization direction passes through the active mirror 60, the low-order aberration is generated, and the laser with the first aberration and the polarization direction of the first polarization direction is formed. After the above laser enters the low-order aberration compensation structure 50, it is first transmitted through the first polarization beamsplitter 10 (as shown in Figure 1The laser is reflected by the wave surface adjusting structure 20, and the wave surface and the polarization direction of the laser are changed, and the laser with the first aberration and the second polarization direction is formed. The laser enters the landing point adjusting structure 30, and the landing point adjusting structure 30 can reflect the landing point of the laser on the first polarization beamsplitter 10, and the landing point area of the laser on the first polarization beamsplitter 10 is overlapped with the transmission area of the laser. The laser emitted from the low-order aberration compensation structure 50 is rotated by 90° compared with the incident laser, the polarization direction is changed from the first polarization direction to the second polarization direction, the emission direction is opposite to the incident direction of the laser, and the aberration is the same as the incident laser, still with the first aberration. The above-mentioned laser can enter the active mirror 60 again in the direction opposite to the incident laser, and the second aberration is generated after the second amplification of the active mirror 60, and the second aberration can offset the first aberration, so that the astigmatism of the laser emitted from the active mirror 60 is compensated. The low-order aberration compensation structure has low cost, simple structure and convenient processing.

[0047] As shown in Figure 1 In the embodiment, the first polarization direction is horizontal, and the second polarization direction is vertical. The first polarization direction and the second polarization direction form a vertical relationship.

[0048] The first polarization beamsplitter 10 can transmit the laser of the first polarization direction and reflect the laser of the second polarization direction. When the laser of the first polarization direction falls on the first polarization beamsplitter 10, the first polarization beamsplitter 10 can transmit the laser. When the polarization direction of the laser is changed from the first polarization direction to the second polarization direction, the laser can be reflected by the first polarization beamsplitter 10, so that the laser entering the low-order aberration compensation structure 50 and the laser reflected from the low-order aberration compensation structure 50 have the properties of coaxial, reverse and polarization direction change.

[0049] Specifically, the 90° rotation of the laser wave surface exchanges the horizontal and vertical directions of the laser entering the active mirror 60 and the laser emitted from the active mirror 60, and the aberration superposition caused by the twice through the amplifier realizes the self-compensation of the horizontal astigmatism. This compensation of the astigmatism is independent of the size of the astigmatism, and can realize the dynamic compensation in the full range.

[0050] The principle is as follows:

[0051] Zernike polynomial is a commonly used aberration representation method, for example, low-order aberration horizontal astigmatism Defocus The expressions in polar coordinates (r, θ) are respectively:

[0052]

[0053] Therefore, for only horizontal astigmatism The active mirror amplifier, let its first aberration be:

[0054]

[0055] After rotating 90° in the second pass, the second aberration is:

[0056]

[0057] The total aberration is:

[0058] S(r,θ)=S1(r,θ)+S2(r,θ)=0

[0059] Furthermore, such as Figure 1 As shown, in this embodiment, the wavefront adjustment structure 20 includes a first reflector 21 and a second reflector 22. The laser light with a first polarization direction transmitted through the first polarizing beam splitter 10 passes through the first reflector 21 and the second reflector 22 in sequence. The polarization direction of the laser light reflected from the second reflector 22 changes from the first polarization direction to the second polarization direction.

[0060] The wavefront adjustment structure 20 consists of two reflectors, which is simple in structure and low in cost.

[0061] Specifically, after the laser beam with the first polarization direction passes through the first reflecting mirror 21 and the second reflecting mirror 22 in sequence, the wavefront rotates by 90°. Correspondingly, the rotation of the wavefront also causes a rotation of the polarization direction. The laser beam changes from horizontal polarization to vertical polarization.

[0062] like Figure 1 As shown, in this embodiment, the landing point adjustment structure 30 includes a third reflector 31 and a fourth reflector 32. The laser with the second polarization direction passes through the third reflector 31 and the fourth reflector 32 in sequence. The landing point of the laser reflected from the fourth reflector 32 is located on the first polarization beam splitter 10 and coincides with the transmission point of the laser with the first polarization direction on the first polarization beam splitter 10.

[0063] The landing point adjustment structure 30 consists of two reflectors, which are easy to process and have low production costs.

[0064] Specifically, the laser emitted from the wavefront adjustment structure 20 has a vertical polarization direction. After passing through the third reflector 31 and the fourth reflector 32 in sequence, the vertically polarized laser returns to the first polarizing beam splitter 10, and the laser's landing area on the first polarizing beam splitter 10 coincides with the laser's transmission area on the first polarizing beam splitter 10. This results in the laser emitted from the low-order aberration compensation structure 50 forming a laser with opposite directions and a 90° rotation in both the wavefront and polarization direction compared to the incident laser.

[0065] As shown in Figure 1 In the embodiment, the low-order aberration compensation structure 50 of the laser further comprises a focal length adjustment structure 40, which is arranged on the light path of the laser.

[0066] The first polarization beamsplitter 10, the wavefront adjustment structure 20 and the landing point adjustment structure 30 can solve the problem of horizontal astigmatism in the low-order aberration, and the problem of defocus in the low-order aberration needs to be adjusted by the focal length adjustment structure 40. Therefore, the low-order aberration compensation structure 50 of the application further comprises a focal length adjustment structure 40, which only needs to be arranged on the light path of the laser to achieve the adjustment effect of the focal length.

[0067] Preferably, as shown in Figure 1 In the embodiment, the focal length adjustment structure 40 comprises a spherical lens.

[0068] Specifically, in the embodiment, the focal length adjustment structure 40 only comprises one lens.

[0069] Further preferably, as shown in Figure 1 In the embodiment, the focal length adjustment structure 40 is arranged between the landing point adjustment structure 30 and the first polarization beamsplitter 10.

[0070] The space between the landing point adjustment structure 30 and the first polarization beamsplitter 10 is relatively sufficient, so the focal length adjustment structure 40 can be arranged between the landing point adjustment structure 30 and the first polarization beamsplitter 10.

[0071] On the other hand, the application also provides a double-pass active mirror amplifier.

[0072] Figure 2 The structure schematic diagram of the double-pass active mirror amplifier provided by the embodiment of the application is shown, wherein Figure 2 The laser incident light path 1 of the laser double-pass laser active mirror is shown; Figure 3 The structure schematic diagram of the double-pass active mirror amplifier provided by the embodiment of the application is shown, wherein Figure 3 The laser exit light path of the laser double-pass laser active mirror is shown; Figure 4 The structure schematic diagram of the double-pass active mirror amplifier provided by the embodiment of the application is shown, wherein Figure 4 The laser incident light path 1 and the laser exit light path 2 of the laser double-pass laser active mirror are shown.

[0073] As shown in Figures 2 to 4 The double-pass active mirror amplifier of the embodiment comprises an active mirror 60 and a low-order aberration compensation structure 50.

[0074] The active mirror 60 is used to receive the laser with the first polarization direction; the low-order aberration compensation structure 50 is arranged at the rear end of the active mirror 60, the low-order aberration compensation structure 50 is the low-order aberration compensation structure 50 described above, and the low-order aberration compensation structure 50 is used to receive the laser with the first polarization direction transmitted from the active mirror 60 and reflect the laser with the second polarization direction to the active mirror 60.

[0075] Specifically, the low-order aberration compensation structure 50 is arranged at the rear end of the active mirror 60, and the laser with the first polarization direction first passes through the active mirror 60 to generate a low-order aberration, thereby forming the laser with the first aberration and the first polarization direction. After the above laser enters the low-order aberration compensation structure 50, it is first transmitted through the first polarization beamsplitter 10, forms a transmission area on the wave surface adjustment structure 20, and then passes through the reflection of the wave surface adjustment structure 20. The wave surface and the polarization direction of the laser emitted from the wave surface adjustment structure 20 are changed, and the laser with the first aberration and the second polarization direction is formed. The above laser enters the landing point adjustment structure 30, and the landing point adjustment structure 30 can reflect the landing point of the above laser to the first polarization beamsplitter 10, and make the landing point area of the laser on the first polarization beamsplitter 10 coincide with the transmission area of the laser. Finally, the laser emitted from the low-order aberration compensation structure 50 is compared with the incident laser, the wave surface is rotated by 90°, the polarization direction is changed from the first polarization direction to the second polarization direction, the emission direction is opposite to the incident direction of the laser, the aberration is the same as the incident laser, and still has the first aberration. The above laser can enter the active mirror 60 again along the direction opposite to the incident laser, and generate a second aberration after passing through the active mirror 60. The second aberration can be offset with the first aberration, so that the astigmatism of the laser emitted from the active mirror 60 is compensated.

[0076] As shown in Figures 2 to 4 In this embodiment, the double-pass active mirror amplifier further includes a second polarization beamsplitter 70, which is arranged at the front end of the active mirror 60 and can transmit the laser with the first polarization direction and reflect the laser with the second polarization direction.

[0077] The second polarization beamsplitter 70 has the same function as the first polarization beamsplitter 10, that is, it can transmit laser light of the first polarization direction and reflect laser light of the second polarization direction. Laser light of the first polarization direction falls on the second polarization beamsplitter 70 from the working direction of the second polarization beamsplitter 70, and is transmitted through the second polarization beamsplitter 70 into the active mirror 60 for first amplification, and then enters the low-order aberration compensation structure 50 to change the polarization direction from the horizontal direction to the vertical direction, and then returns to the active mirror 60 in the direction opposite to the incident direction for second amplification. At this time, the laser low-order aberration is compensated, and the polarization direction is vertical. The above-mentioned laser light falling on the second polarization beamsplitter 70 can be reflected by the second polarization beamsplitter 70 to change direction and enter other optical devices for subsequent adjustment.

[0078] The application also provides a laser (not shown in the figure), which comprises a double-pass active mirror amplifier 80, which is the double-pass active mirror amplifier described above. Since the double-pass active mirror amplifier has the advantages of simple structure, good low-order aberration compensation effect and low cost, the laser with the double-pass active mirror amplifier also has the above-mentioned advantages.

[0079] The double-pass active mirror amplifier 80 in the related art usually first amplifies laser light by the double-pass active mirror amplifier to generate aberration. A mirror is arranged at the rear end of the double-pass active mirror amplifier, and the laser light changes the optical path after being reflected by the mirror and enters the double-pass active mirror amplifier again for second amplification. For the ordinary mirror method, the aberration of the laser light passing through the amplifier twice is the same, that is, the double-pass aberration is twice the single-pass aberration. In the application, the low-order aberration compensation structure 50 is used instead of the mirror, which realizes 90° rotation of the laser wave surface and 90° rotation of the polarization direction, and enables the laser light to be emitted in the direction opposite to the incident direction. The astigmatism of the laser light passing through the double-pass amplifier twice is mutually compensated, and then the defocus is compensated by the spherical lens to realize full compensation of the low-order aberration.

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the application, and not to limit them. Although the application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for part or all of the technical features. Such modifications or substitutions do not change the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the application.

Claims

1. A low-order aberration compensation structure, characterized by, Comprising: a first polarization beamsplitter (10) capable of transmitting laser light of a first polarization direction and reflecting laser light of a second polarization direction; a wavefront adjusting structure (20) configured to receive laser light of the first polarization direction and change the polarization direction of the laser light from the first polarization direction to the second polarization direction by reflection; a spot adjusting structure (30) configured to receive laser light of the second polarization direction and reflect the spot of the laser light of the second polarization direction onto the first polarization beamsplitter (10) so that the spot area of the laser light of the second polarization direction on the first polarization beamsplitter (10) coincides with the transmission area of the laser light of the first polarization direction on the first polarization beamsplitter (10); the wavefront and polarization direction of the laser light exiting the low-order aberration compensation structure are rotated by 90°, so that the laser light can exit in the opposite direction of the incident direction.

2. The low-order aberration compensation structure of claim 1, wherein, The first polarization direction is the horizontal direction, and the second polarization direction is the vertical direction.

3. The low-order aberration compensation structure of claim 1, wherein, The wavefront adjusting structure (20) comprises a first mirror (21) and a second mirror (22), and the laser light of the first polarization direction transmitted from the first polarization beamsplitter (10) passes through the first mirror (21) and the second mirror (22) in sequence, and the polarization direction of the laser light reflected from the second mirror (22) is changed from the first polarization direction to the second polarization direction.

4. The low-order aberration compensation structure of claim 1, wherein, The spot adjusting structure (30) comprises a third mirror (31) and a fourth mirror (32), and the laser light of the second polarization direction passes through the third mirror (31) and the fourth mirror (32) in sequence, and the spot area of the laser light reflected from the fourth mirror (32) is located on the first polarization beamsplitter (10) and coincides with the transmission area of the laser light of the first polarization direction on the first polarization beamsplitter (10).

5. The low-order aberration compensating structure (50) according to any one of claims 1 to 4, characterized in that The low-order aberration compensation structure (50) of the laser light further comprises: a focal length adjusting structure (40) disposed on the optical path of the laser light.

6. The low-order aberration compensation structure (50) according to claim 5, characterized in that The focal length adjusting structure (40) comprises a spherical lens.

7. The low-order aberration compensating structure (50) according to claim 5, characterized in that The focal length adjusting structure (40) is disposed between the spot adjusting structure (30) and the first polarization beamsplitter (10).

8. A two-pass activated mirror amplifier characterized by, Comprising: an activation mirror (60) for receiving laser light of a first polarization direction; a low-order aberration compensation structure (50) disposed at the rear end of the activation mirror (60), the low-order aberration compensation structure (50) being the low-order aberration compensation structure (50) of any one of claims 1 to 7, the low-order aberration compensation structure (50) for receiving laser light of the first polarization direction transmitted from the activation mirror (60) and reflecting laser light of a second polarization direction to the activation mirror (60).

9. The two-pass active mirror amplifier of claim 8, wherein, The double-pass activation mirror amplifier further comprises: a second polarization beamsplitter (70) disposed upstream of the activation mirror (60), the second polarization beamsplitter (70) capable of transmitting laser light of a first polarization direction and reflecting laser light of a second polarization direction.

10. A laser, characterized by Comprising: A double-pass active mirror amplifier (80) as claimed in any one of claims 8 to 9.

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