Sunlight transversely pumped fiber laser with staggered core arrangement

Abstract

The present invention relates to the field of laser technology, and in particular to a solar light transversely pumped fiber laser with a staggered core arrangement, comprising: a pump cavity, an annular off-axis parabolic mirror, and an optical fiber bundle, wherein the pump cavity comprises a cover plate, a substrate, and a cylindrical base; the outer surfaces of the cover plate, the substrate, and the cylindrical base are all coated with a high-reflectivity film to form a light trap that limits the transmission of solar light; the annular off-axis parabolic mirror has a reflective surface on the side facing the pump cavity; the optical fiber bundle is fixed to the upper surface of the substrate in a longitudinally staggered alternating arrangement; an annular radiation window is formed between the upper surface of the substrate and the lower surface of the cover plate for receiving solar pump light; the annular off-axis parabolic mirror reflects the solar pump light and converges it into the radiation window; after the solar pump light enters the pump cavity through the radiation window, it is absorbed by the staggered cores of the optical fiber bundle under the action of the light trap. The advantage of the present invention is that the light trap is combined with the staggered alternating optical fiber bundle, further optimizing the transverse pumping efficiency.

Description

Technical Field

[0001] The present invention relates to the field of laser technology, and in particular to a sunlight transversely pumped fiber laser with a staggered fiber core arrangement. Background Art

[0002] Solar-pumped fiber lasers, a technology that directly utilizes solar energy to achieve laser output, have garnered widespread attention in recent years. Existing technologies are primarily categorized into two main types, depending on their operating principles: indirect pumping schemes based on energy transfer from sensitizer fluorescence radiation and direct solar pumping schemes.

[0003] The indirect pumping scheme converts sunlight into fluorescent photons that match the absorption band of rare earth ions through a sensitizer. It mainly includes three typical structures:

[0004] Low-concentration-ratio annular lens structure: A toroidal lens focuses sunlight, forming a circular spot on the surface of a neodymium-doped optical fiber immersed in a liquid sensitizer (such as rhodamine 6G). This structure forms a "greenhouse cavity" with gold-plated cavity sidewalls and a high-reflectivity mirror (HR), achieving efficient reflection of fluorescent photons. However, it requires sophisticated optical components and a sun-tracking system, resulting in a complex structure and high cost.

[0005] Liquid LSC structure: Its innovative non-focusing planar design eliminates the need for a focusing system and tracking mechanism. Direct contact between the liquid sensitizer and the multilayer dielectric mirror allows for simultaneous reception of both direct and diffuse light. However, due to the lack of total internal reflection, significant fluorescence photon loss occurs, necessitating the use of longer gain fibers for compensation.

[0006] Solid-state LSC thin film structure: The sensitizer is solidified into a fluorinated polyurethane film, with an air gap between it and the reflector to achieve total internal reflection. Although this solves the stability problem of the liquid structure, the film preparation process is complex and uniformity control is difficult.

[0007] Direct pumping solutions couple sunlight directly into optical fibers through a concentrating system. Representative technologies include an off-axis Fresnel lens and a compound parabolic waveguide structure. This two-stage concentrating system focuses sunlight into a ring-shaped pump cavity. While achieving a 21.4% concentration efficiency, the structure is complex and the optical-to-optical conversion efficiency is only 3.7%.

[0008] Off-axis parabolic mirror array + 3D-CPC structure: This structure uses a multi-mirror array and a composite reflective concentrator to increase pump power, reaching an output of 12.2 W. However, the system is bulky and the efficiency is still less than 2.5%.

[0009] Both of the above solutions have the following problems:

[0010] The indirect pumping scheme is limited by the stability and conversion efficiency of the sensitizer; the direct pumping scheme has a complex focusing system and it is difficult to achieve both high power and high efficiency; the fiber arrangement of the existing lateral pumping structure leads to uneven absorption of the pump light; and the system integration is low, which is not conducive to practical application. Summary of the Invention

[0011] Based on this, the present invention proposes a solar-powered transversely pumped fiber laser with a staggered core arrangement. By staggering and alternating the fiber bundles, a close-packed core arrangement with no gaps is formed in the projection direction, allowing light of any incident angle to intersect the cores and achieve a certain proportion of effective absorption. Compared to a regular rectangular array arrangement, the staggered core arrangement creates multiple, intersecting absorption paths in the incident direction, significantly enhancing the equivalent absorption path length of solar radiation.

[0012] To achieve the above-mentioned purpose, the technical solution created by the present invention is implemented as follows: a solar light transversely pumped fiber laser with a staggered core arrangement, comprising: a pump cavity, the pump cavity comprising a cover plate, a substrate and a cylindrical base, the cover plate and the substrate being arranged opposite to each other, the cylindrical base being located between the cover plate and the substrate, and the three together forming an annular side surface; the outer surfaces of the cover plate, the substrate and the cylindrical base are all coated with a high reflectivity film to form a light trap that limits the transmission of solar light; an annular off-axis parabolic mirror, the annular off-axis parabolic mirror being arranged on the outside of the pump cavity The annular off-axis parabolic mirror has a reflecting surface on the side facing the pump cavity; the optical fiber bundle is alternately wound on the substrate along the axial offset of the pump cavity; an annular radiation window is formed between the upper surface of the substrate and the lower surface of the cover plate, and the annular radiation window is located in the opening area of ​​the annular side and is used to receive the solar pump light focused by the annular off-axis parabolic mirror; the annular off-axis parabolic mirror reflects the solar pump light and focuses it to the annular radiation window. After the solar pump light enters the pump cavity through the annular radiation window, it is absorbed by the offset core of the optical fiber bundle under the action of the light trap.

[0013] Furthermore, it also includes a packaging structure, which uses ultraviolet curing resin with a high matching refractive index to fill the annular radiation window to suppress Fresnel reflection at the interface between the ultraviolet curing resin and the upper surface of the substrate and the lower surface of the cover plate, and to fix the optical fiber bundle.

[0014] Furthermore, the optical fiber bundle is an active optical fiber bundle with the coating removed, so as to avoid absorption loss and transmission obstruction of the coating material on the pump light.

[0015] Furthermore, the optical fiber bundle adopts neodymium-doped double-clad silica optical fiber.

[0016] Furthermore, the process of winding the optical fiber bundle on the substrate in an axially staggered manner along the pump cavity includes: the first winding forms a reference layer, and the subsequent windings are centered on the reference layer and alternately shifted in the forward and reverse directions along the axial direction, so that the cores of the optical fiber bundle form a gapless array in the projection direction perpendicular to the annular radiation window.

[0017] Furthermore, the fiber bundle is wound in layers radially outward from the inside of the pump cavity, including an inner section comprised of at least two single-layer first fiber coils stacked one on top of the other. An outer section, arranged outside the inner section, comprises at least three double-layer second fiber coils stacked one on top of the other. Each double-layer second fiber coil is composed of two stacked single-layer first fiber coils. Each first fiber coil contains the same number of pre-set fiber coils, and axial displacement control is achieved through a reference layer.

[0018] Furthermore, based on the radial direction of the pump cavity, the inclination angle of each fiber coil group is 1° to 1.5°.

[0019] Furthermore, the calculation formula for the reflection focal length of the annular off-axis parabolic mirror is: ;

[0020] in, f represents the reflection focal length of the annular off-axis parabolic mirror; γ Indicates the half angle of solar divergence; d It represents the diameter of the sun's converging spot, which is equal to the total width of the annular radiation window.

[0021] Furthermore, based on the reflection focal length and field of view of the annular off-axis parabolic mirror, the inner diameter and outer diameter of the annular off-axis parabolic mirror are obtained as follows:

[0022] ;

[0023] ;

[0024] in, D in represents the inner diameter of the annular off-axis parabolic mirror; D out represents the outer diameter of the annular off-axis parabolic mirror; θ represents the half-angle of the field of view of the annular off-axis parabolic mirror; L p Represents the diameter of the pump cavity.

[0025] The invention can achieve the following beneficial effects:

[0026] 1) The composite optical structure consisting of an annular off-axis parabolic mirror and a planar pump cavity significantly improves the light energy utilization efficiency of the sunlight-transversely pumped fiber laser.

[0027] 2) Combining the optical trap with the staggered and alternating optical fiber bundles further optimizes the lateral pumping efficiency.

[0028] 3) The staggered arrangement, based on the random distribution of incident angles of non-sequential light, creates a close-packed, gapless core arrangement in the projection direction, allowing light of any incident angle to intersect the core and be partially absorbed. Compared to a regular rectangular array, the multiple staggered absorption paths significantly extend the equivalent optical path.

[0029] 4) This invention comprehensively considers the impact of solar divergence angle, fiber bend radius, and winding pitch on mode preservation and absorption efficiency. A design with a δ=1.3° tilt angle and 25 turns per group achieves high-density nesting within a limited space, improving effective fiber core coverage per unit volume. Compared to regular rectangular arrays, this solution offers advantages in fiber space utilization, occlusion suppression, and light capture probability, further improving overall pump energy efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The accompanying drawings, which constitute part of the present invention, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0031] Figure 1 2 is a schematic structural diagram of a solar light transversely pumped fiber laser with a staggered core arrangement provided by an embodiment of the present invention;

[0032] Figure 2 is a cross-sectional view of a solar light transversely pumped fiber laser with a staggered core arrangement provided by an embodiment of the present invention along a plane where the axis is located;

[0033] Figure 3 is a schematic diagram of a longitudinally staggered and alternately arranged optical fiber bundle according to an embodiment of the present invention;

[0034] Figure 4 is a schematic structural diagram of a first optical fiber coil group with a single-layer structure according to an embodiment of the present invention;

[0035] Figure 5 It is a structural schematic diagram of 8 groups of optical fiber coils arranged in a staggered alternating manner and in a regular rectangular array according to an embodiment of the present invention.

[0036] The reference numerals include: 1. annular off-axis parabolic mirror; 2. optical fiber bundle; 3. cover plate; 4. substrate; 5. cylindrical base; 6. solar pump light. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not constitute a limitation of the present invention.

[0038] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

[0039] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying 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. In addition, the terms "first", "second" and the like are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, features defined as "first", "second" and the like may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0040] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to internal connections between two components. Those skilled in the art can understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0041] The present invention will be described in detail below with reference to the embodiments.

[0042] like Figures 1 to 5 As shown, an embodiment of the present invention provides a sunlight transversely pumped fiber laser with a staggered core arrangement, comprising: a pump cavity, a ring-shaped off-axis parabolic mirror 1, an optical fiber bundle 2 and a packaging structure.

[0043] The pump cavity includes a cover plate 3, a substrate 4, and a cylindrical base 5. The cover plate 3 and substrate 4 are arranged opposite each other, with the cylindrical base 5 located between them. Together, the three form an annular side surface. The cover plate 3, substrate 4, and cylindrical base 5 are coaxially arranged. Specifically, the cover plate 3 and substrate 4 are made of quartz, which has excellent high-temperature resistance and light transmission properties, and can prevent the material from absorbing and losing solar pump light. The cover plate 3 and substrate 4 have the same structure, both being circular rings with an inner diameter that matches the outer diameter of the cylindrical base 5. The ends of the cylindrical base 5 are respectively located within the circular rings of the cover plate 3 and substrate 4. The upper surface of the cylindrical base 5 is flush with the upper surface of the cover plate 3, and its lower surface is flush with the lower surface of the substrate 4. The cylindrical base 5 is made of a high-strength aluminum alloy, such as 7A09 or 6061.

[0044] The outer surfaces of the cover plate 3, substrate 4 and cylindrical base 5 are coated with a high-reflectivity film to form a light trap that limits the transmission of solar light, thereby extending the transmission path of the solar pump light 6 that is reflected back and forth in the pump cavity, and creating a stable optical transmission environment for improving the core absorption rate of the optical fiber bundle 2.

[0045] The annular off-axis parabolic mirror 1 is arranged outside the pump cavity, and the side of the annular off-axis parabolic mirror 1 facing the pump cavity has a reflecting surface.

[0046] The optical fiber bundle 2 is alternately wound around the upper surface of the substrate 4, staggered along the axial direction of the pump cavity. An annular radiation window is formed between the upper surface of the substrate 4 and the lower surface of the cover plate 3. Located in the opening area of ​​the annular side, the annular radiation window receives solar pump light 6 focused by the annular off-axis parabolic mirror 1. The annular off-axis parabolic mirror 1 reflects and converges the solar pump light 6 into the annular radiation window. After entering the pump cavity through the annular radiation window, the solar pump light 6 is absorbed by the staggered core of the optical fiber bundle 2 due to the optical trapping effect.

[0047] The encapsulation structure uses a UV-curable resin with a highly matched refractive index, filling the annular radiation window. This serves to suppress Fresnel reflections at the interfaces between the UV-curable resin and the upper surface of the substrate 4 and the lower surface of the cover plate 3, as well as to secure the optical fiber bundle 2. In this embodiment, the UV-curable resin is Norland Optical Adhesive (NOA85), which effectively transmits sunlight as a similar medium. The highly matched refractive index of the UV-curable resin closely matches the material properties (refractive index) of the substrate 4 and cover plate 3.

[0048] The optical fiber bundle 2, cover plate 3, substrate 4, cylindrical base 5, and packaging structure together form the planar pump cavity. The annular off-axis parabolic mirror 1 forms a continuous annular light band on the annular side of the planar pump cavity, preventing uneven heating. Light is reflected multiple times within the pump cavity (i.e., the annular radiation window formed between the upper surface of substrate 4 and the lower surface of cover plate 3), extending the effective absorption path.

[0049] Furthermore, fiber bundle 2 is an active fiber bundle with the coating removed to avoid absorption loss and transmission obstruction of the pump light by the coating material. In this embodiment, fiber bundle 2 uses neodymium-doped double-clad silica fiber as the gain medium, with the core and inner cladding diameters of the fiber being 5 μm and 125 μm, respectively.

[0050] The process of winding the optical fiber bundle 2 on the substrate 4 along the axial direction of the pump cavity in an alternating manner includes: the first winding forms a reference layer, and the subsequent adjacent optical fiber bundles 2 are alternately shifted in the forward and reverse directions along the axial direction with the reference layer as the center (the vertical displacement difference between adjacent fiber cores is 5μm), so that all the fiber cores form a gapless array in the projection direction perpendicular to the annular radiation window (such as Figure 4 As shown in Figure 2 , the longitudinally staggered alternating arrangement (axially of the pump cavity) significantly improves the energy coupling efficiency of the pump cavity by increasing the number of times light passes through different fiber cores, extending the absorption path, and reducing the light escape gap. The tilt angle δ of the longitudinally staggered alternating arrangement of fiber bundle 2 is 1° to 1.5° relative to the radial direction of the pump cavity. Typically, adjacent fiber loops are tangent to each other.

[0051] To accurately simulate the transmission of sunlight through the longitudinally staggered, alternating arrangement of fiber bundle 2, a large number of light samples were used for non-sequential tracing to characterize the irregular refraction and deflection paths of light within the core array of fiber bundle 2. The longitudinally staggered, alternating arrangement of fiber bundle 2 is based on the random distribution of light. The theoretical analysis simplifies the transmission and deflection of light between the cores of different fiber bundles 2.

[0052] like Figure 3 As shown in (a), during the physical modeling process, the refraction path of any light ray A penetrating the core of fiber bundle 2 may overlap with the initial transmission vector of another light ray B. Therefore, it is reasonable to simplify the multiple complex directional deflections experienced by light rays passing through the core of fiber bundle 2 to improve computational efficiency.

[0053] like Figure 3 As shown in (b) of Figure 1, in the pump cavity, only the reflected propagation path of the light from the initial vector direction through the optical trap is analyzed, ignoring the refractive deflection caused by the light penetrating the fiber core. For a solar ray with a given incident angle, the intersection length of the propagation path with the core of fiber bundle 2 and its proportion of the total optical propagation path are equivalent to the proportion effectively absorbed by the fiber core and are considered the equivalent absorption probability. To improve calculation accuracy, all rays from the time of incidence until they reach the bottom of the pump cavity are considered.

[0054] Furthermore, the optical fiber bundle 2 is wound in layers radially outward from the inside of the pump cavity, comprising an inner section comprised of at least two sets of single-layer first optical fiber coils stacked one on top of the other. An outer section, arranged outside the inner section, comprises at least three sets of double-layer second optical fiber coils stacked one on top of the other. Each double-layer second optical fiber coil is composed of two stacked single-layer first optical fiber coils, each of which includes multiple optical fiber coils stacked one on top of the other.

[0055] In this embodiment, each first fiber coil group is wound radially from the inside outward, consisting of 25 turns (i.e., 25 fiber coils). With the first fiber coil serving as the reference layer, the subsequent 24 fiber coils are centered around the reference layer, alternating between positive and negative vertical offsets along the axial direction, forming a "positive-negative-positive" alternating pattern. This pattern continues until 12 turns of positive offset and 12 turns of negative offset have been achieved. The vertical displacement difference between the cores of adjacent fiber bundles 2 is 5 μm.

[0056] like Figure 4 As shown in , fiber bundle 2 utilizes a longitudinally staggered alternating arrangement, significantly optimizing the spatial utilization of the fiber arrangement, reducing optical obstruction between adjacent fiber cores, and improving the energy coupling efficiency of solar radiation within the pump cavity. The first fiber coil group has a trapezoidal outer profile. Its design parameters include: length L0 along the pump cavity radial direction; top width w1 near the pump cavity; bottom width w2 away from the pump cavity; and inclination angle δ relative to the pump cavity radial direction.

[0057] In this embodiment, δ = 1.3° (i.e., adjacent fiber coils are tangent), w1 = 0.135 mm, w2 ≈ 0.2637 mm, and L0 ≈ 2.8352 mm. Fiber bundle 2 is 190 m long, with the first coil wound around a 300 mm diameter. Calculations indicate a total of approximately 200 coils, with each coil group consisting of 25 coils. Eight coil groups (two single-layer first coil groups and three double-layer second coil groups) are arranged radially along the pump cavity, ensuring seamless overlap of the fiber cores of fiber bundle 2 perpendicular to the annular radiation window.

[0058] To evaluate the effect of the arrangement optimization, a regular rectangular array arrangement of fiber bundle 2 was simultaneously designed in the same pump cavity structure. The purpose was to intuitively compare the differences in the solar radiation energy absorption characteristics of the two fiber arrangements.

[0059] The staggered, alternating arrangement of fiber bundle 2 and the eight fiber coils in the regular rectangular array all follow a uniform numbering convention, numbered A, B, C1, C2, D1, D2, E1, and E2 from the inside out along the radial direction of the pump cavity. A and B are single-layer fiber coils, while C1 / C2, D1 / D2, and E1 / E2 are double-layer fiber coils.

[0060] like Figure 5 As shown in (a), fiber bundle 2 is arranged in an alternating, staggered configuration: the cores of adjacent fiber coils are offset both radially and longitudinally within the pump cavity, ensuring that incident light travels through different cores multiple times, increasing the absorption path length. Furthermore, a double-layer arrangement (e.g., C1 / C2, D1 / D2, etc.) ensures tight radial coverage of fiber bundle 2, minimizing gaps for light escape.

[0061] like Figure 5 As shown in (b), the fiber bundles 2 are arranged in a regular rectangular array. This arrangement involves the fiber bundles 2 being arranged in a regular, uniform pattern, with adjacent fiber coils adhered to the top surface of substrate 4 in parallel and equidistant from each other. The cores of all fiber bundles 2 projected onto the annular radiation window form a regular rectangular grid, with fixed gaps between adjacent cores. The core centers of the fiber bundles 2 are strictly aligned, with no vertical offset. Due to this regular arrangement, light may pass directly through the gaps between the fibers, reducing the effective absorption rate.

[0062] In each fiber coil group, the fiber is wound gradually from the inside to the outside along the radial direction of the pump cavity to 25 coils. The total radial depth of the pump cavity is L t (i.e. the annular width of the cover plate 3). The total width w of the pumping area that transmits sunlight t The pump cavity window width w m It is determined by the thickness of the substrate 4 and the cover plate 3 on both sides. In this embodiment, the thickness of the substrate 4 and the cover plate 3 are both 1 mm thick quartz plates.

[0063] L t =5L0=14.176mm, w t =w m +2mm=2.778mm. In this embodiment, the pump cavity window width w m =0.778.

[0064] Furthermore, the calculation formula for the reflection focal length of the annular off-axis parabolic mirror 1 is: ;

[0065] in, f is the reflection focal length of the annular off-axis parabolic mirror 1; γ Diverge half an angle for the sun; d is the diameter of the sun's converging spot, which is equal to the total width of the annular radiation window.

[0066] In this embodiment, the solar divergence half angle γ ≈0.265°, d= w t =2.778mm, f ≈300.31mm.

[0067] Based on the reflection focal length and field angle of the annular off-axis parabolic mirror 1, the inner diameter and outer diameter of the annular off-axis parabolic mirror 1 are obtained as follows:

[0068] ;

[0069] ;

[0070] in, D in represents the inner diameter of the annular off-axis parabolic mirror 1; D out represents the outer diameter of the annular off-axis parabolic mirror 1; θ represents the field of view half angle of the annular off-axis parabolic mirror 1; L p represents the diameter of the pump cavity, which is L p =2L t +Diameter of the cylindrical base 5.

[0071] In this embodiment, the field of view half angle θ When ±30° is selected, the inner diameter of the annular off-axis parabolic mirror 1 is D in 0.68m ， Outer diameter of annular off-axis parabolic mirror 1 D out It is 1.37m.

[0072] The above specific embodiments do not limit the scope of protection of the present invention. Those skilled in the art will appreciate that various modifications, combinations, sub-combinations, and substitutions may be made based on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention are intended to be included within the scope of protection of the present invention.

Claims

1. A solar light transversely pumped fiber laser with staggered core arrangement, characterized in that: include: A pump cavity, comprising a cover plate, a substrate, and a cylindrical base, wherein the cover plate and the substrate are arranged opposite each other, and the cylindrical base is located between the cover plate and the substrate, and the three together form an annular side surface; the outer surfaces of the cover plate, the substrate, and the cylindrical base are coated with a high-reflectivity film to form a light trap that limits the transmission of sunlight; An annular radiation window is formed between the upper surface of the substrate and the lower surface of the cover plate, and the annular radiation window is located in the opening area of ​​the annular side surface and is used to receive the solar pump light concentrated by the annular off-axis parabolic mirror; an annular off-axis parabolic mirror, the annular off-axis parabolic mirror being arranged outside the pump cavity, and the side of the annular off-axis parabolic mirror facing the pump cavity having a reflecting surface; an optical fiber bundle, wherein the optical fiber bundle is staggered and alternately wound on the substrate along the axial direction of the pump cavity; The annular off-axis parabolic mirror reflects the solar pump light and converges it to the annular radiation window. After the solar pump light enters the pump cavity through the annular radiation window, it is absorbed by the dislocated core of the optical fiber bundle under the action of the light trap.

2. The solar light transversely pumped fiber laser with staggered core arrangement according to claim 1, characterized in that: It also includes a packaging structure, which uses ultraviolet curing resin with a high matching refractive index to fill the annular radiation window, so as to suppress Fresnel reflection at the interface between the ultraviolet curing resin and the upper surface of the substrate and the lower surface of the cover plate, and to fix the optical fiber bundle.

3. The solar light transversely pumped fiber laser with staggered core arrangement according to claim 1, characterized in that: The optical fiber bundle is an active optical fiber bundle with the coating removed, so as to avoid absorption loss and transmission obstruction of the coating material on the pump light.

4. The solar light transversely pumped fiber laser with staggered core arrangement according to claim 3, characterized in that: The optical fiber bundle adopts neodymium-doped double-clad quartz optical fiber.

5. The solar light transversely pumped fiber laser with staggered core arrangement according to claim 1, characterized in that: The process of winding the optical fiber bundle on the substrate in an axially staggered manner along the pump cavity includes: the first winding forms a reference layer, and the subsequent windings are centered on the reference layer and alternately perform forward and reverse staggered displacements along the axial direction, so that the cores of the optical fiber bundle form a gapless array in the projection direction perpendicular to the annular radiation window.

6. The solar light transversely pumped fiber laser with staggered core arrangement according to claim 5, characterized in that: The optical fiber bundle is wound in layers from inside to outside along the radial direction of the pump cavity, including: Inner section: It is composed of at least two groups of single-layer first optical fiber coils arranged in sequence; Outer section: sleeved outside the inner section, consisting of at least three groups of double-layer second optical fiber coils sleeved in sequence; The second optical fiber coil group with a double-layer structure is formed by stacking two first optical fiber coil groups with a single-layer structure; each of the first optical fiber coil groups includes a plurality of optical fiber coils sequentially arranged from the inside to the outside along the radial direction of the pump cavity.

7. The solar light transversely pumped fiber laser with staggered core arrangement according to claim 6, characterized in that: Based on the radial direction of the pump cavity, the inclination angle of the first optical fiber coil group is 1° to 1.5°.

8. The solar light transversely pumped fiber laser with staggered core arrangement according to claim 1, characterized in that: The calculation formula of the reflection focal length of the annular off-axis parabolic mirror is: ； in, f represents the reflection focal length of the annular off-axis parabolic mirror; γ Indicates the half angle of solar divergence; d It represents the diameter of the sun's focused spot, which is equal to the total width of the annular radiation window.

9. The solar light transversely pumped fiber laser with staggered core arrangement according to claim 8, characterized in that: Based on the reflection focal length and field angle of the annular off-axis parabolic mirror, the inner diameter and outer diameter of the annular off-axis parabolic mirror are obtained as follows: ； ； in, D in represents the inner diameter of the annular off-axis parabolic mirror; D out represents the outer diameter of the annular off-axis parabolic mirror; θ represents the field of view half angle of the annular off-axis parabolic mirror; L p Represents the diameter of the pump cavity.

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