Vortex fiber laser based on gold film-assisted metasurface

Abstract

The invention provides a vortex fiber laser based on a gold film auxiliary metasurface. The vortex fiber laser based on the gold film auxiliary metasurface comprises a pump light source, a wavelength division multiplexer, a collimator and the gold film auxiliary metasurface which are arranged in sequence. The gold film auxiliary metamaterial surface comprises a substrate layer, a gold film layer, a dielectric layer and a nano unit layer which are sequentially stacked and connected, one side of the substrate layer is close to the collimator, one side of the nano unit layer is far away from the collimator, and the nano unit layer comprises a plurality of nano columns which are uniformly arranged; the pump light source is used for emitting laser, the pump light source is connected with the wavelength division multiplexer, the wavelength division multiplexer is connected with the collimator through an optical fiber, the laser is transmitted to the collimator, the collimator transmits the laser to the surface of the gold film auxiliary metasurface, and the surface of the gold film auxiliary metasurface outputs vortex light beams.

Description

Technical Field

[0001] The present invention relates to the field of optical technology, and in particular to a vortex fiber laser based on a gold film-assisted metasurface. Background Art

[0002] A vortex beam is a structured beam that carries orbital angular momentum (OAM). The wavefront is spiral, there is a phase singularity at the center of the beam, and the light intensity presents a ring-shaped distribution with zero intensity at the center. Due to these novel characteristics, OAM vortex beams have broad application prospects in many fields. In optical communication applications, the orbital angular momentum in the vortex beam can be used as a new encoding method to achieve information encoding and expand the capacity of optical communication; in the biomedical field, optical tweezers and optical wrenches have been developed using OAM vortex beams to achieve contactless capture and rotation of particles; in the field of laser processing, OAM vortex beams can be used to prepare chiral micro-nano structures on a large scale; in the field of measurement, the rotational Doppler effect of OAM vortex beams can be used to directly measure the angular velocity of rotating bodies.

[0003] The generation methods of OAM vortex beams can be divided into two categories: extracavity regulation (passive method) and intracavity direct excitation of vortex beams (active method). Extracavity regulation mainly converts Gaussian beams, Hermite-Gaussian beams and other forms of beams outside the cavity into OAM vortex beams, while intracavity regulation directly generates OAM vortex beams in the laser resonant cavity.

[0004] Intracavity modulation is to generate OAM vortex beam directly in the laser resonant cavity by performing gain loss control or inserting vortex phase modulation devices in the laser resonant cavity. Inserting modulation devices is one of the most common methods of intracavity modulation. The basic principle is to insert modulation devices such as spiral phase plates, variable spiral plates (VSP) and spatial light modulators into the cavity to achieve phase modulation of the beam, thereby outputting the desired OAM mode. However, the above optical devices often take up a large space, making the structure of the laser not compact enough. Summary of the invention

[0005] In view of this, an embodiment of the present invention provides a vortex fiber laser based on a gold film-assisted metasurface to eliminate or improve one or more defects existing in the prior art.

[0006] One aspect of the present invention provides a vortex fiber laser based on a gold film-assisted metasurface, wherein the vortex fiber laser based on a gold film-assisted metasurface comprises a pump light source, a wavelength division multiplexer, a collimator and a gold film-assisted metasurface arranged in sequence;

[0007] The gold film-assisted metasurface comprises a substrate layer, a gold film layer, a dielectric layer and a nano-unit layer which are sequentially stacked and connected, one side of the substrate layer is close to the collimator, one side of the nano-unit layer is far from the collimator, and the nano-unit layer comprises a plurality of nano-pillars which are evenly arranged;

[0008] The pump light source is used to emit laser, and the pump light source is connected to a wavelength division multiplexer, and the wavelength division multiplexer is connected to a collimator through an optical fiber, and the laser is transmitted to the collimator, and the collimator transmits the laser to the gold film-assisted metasurface, and the gold film-assisted metasurface outputs a vortex beam.

[0009] By adopting the above scheme, this patent can realize the output of vortex beam with the required topological charge by embedding the full-space metasurface assisted by gold film into the laser cavity. This patent proposes a full-space metasurface assisted by gold film, which can realize a semi-transparent and semi-reflective function. This scheme uses the semi-transparent and semi-reflective function of the gold film to set the gold film on one side of the collimator to complete the reflection. And because the gold film still reflects a Gaussian beam with the same polarization, it is convenient to directly couple the beam back into the laser cavity, and no other devices are required to adjust the polarization, so that the laser oscillates back and forth between the metasurface and the fiber reflector, reducing the use of optical components in the entire system, which is conducive to the further integration of the system; and through the scheme of transmitting the gold film, the adjustment of the beam is completed through the nano-unit layer on the other side to complete the output of the vortex beam.

[0010] In some embodiments of the present invention, the gold film-assisted metasurface is disposed on the end face of an optical fiber connected to an output end of a collimator.

[0011] In some embodiments of the present invention, the substrate layer and the dielectric layer are made of silicon dioxide, the nanorods are made of amorphous silicon, and the gold film layer is made of gold.

[0012] In some embodiments of the present invention, the thickness of the gold film layer is 8 to 12 nm.

[0013] In some embodiments of the present invention, the height of the nanorods is 450-550 nm.

[0014] In some embodiments of the present invention, the distribution period of the nanorods on the nanounit layer is 440-460 nm.

[0015] In some embodiments of the present invention, the top-view plane of the metasurface is a rectangle, and the rectangle is divided into a plurality of triangular areas by connecting the center of gravity of the rectangle as one end of a ray, and the cumulative phase difference of the X-polarization of the output light of the metasurface in the plurality of triangular areas is 2π.

[0016] In some embodiments of the present invention, the metasurface includes 8 triangular regions, and the phase difference of the output light of each triangular region under X-polarized incidence is 0.25π.

[0017] In some embodiments of the present invention, the top-view plane of the gold film-assisted metasurface is a rectangle, and the rectangle is divided into a plurality of triangular areas by connecting the center of gravity of the rectangle as one end of a ray, each triangular area has the same angle at the center of gravity of the rectangle, and the structural parameters of the metasurface units within a single triangular area are the same.

[0018] In some embodiments of the present invention, the vortex fiber laser based on the gold film-assisted metasurface further includes a lens, which is disposed between the collimator and the gold film-assisted metasurface to shrink the light beam and converge the light beam onto the gold film-assisted metasurface.

[0019] In some embodiments of the present invention, the vortex fiber laser based on the gold film-assisted metasurface further includes a fiber reflector, and the fiber reflector is connected to a wavelength division multiplexer.

[0020] Additional advantages, purposes, and features of the present invention will be described in part in the following description, and will become apparent to those skilled in the art after studying the following, or may be learned from the practice of the present invention. The purposes and other advantages of the present invention can be specifically pointed out and obtained in the specification and the accompanying drawings.

[0021] Those skilled in the art will appreciate that the objectives and advantages that can be achieved with the present invention are not limited to the above specific description, and the above and other objectives that can be achieved by the present invention will be more clearly understood from the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The drawings described herein are used to provide a further understanding of the present invention, constitute a part of this application, and do not constitute a limitation of the present invention.

[0023] Figure 1 A schematic diagram of an embodiment of a vortex fiber laser based on a gold film-assisted metasurface of the present invention;

[0024] Figure 2 Schematic diagram of the function of the gold film-assisted metasurface in the present invention;

[0025] Figure 3 (a) is a local schematic diagram of the metasurface;

[0026] Figure 3 (b) is a partial schematic diagram of the metasurface from another angle;

[0027] Figure 3(c) Schematic diagram of simulated reflectivity, transmittance, reflection phase and transmission phase of 8 meta-units;

[0028] Figure 3 (d) Schematic diagram of the metasurface arrangement;

[0029] Figure 4 Schematic diagram of SEM image of the metastructure surface;

[0030] Figure 5 (a) is a schematic diagram of the vortex beam intensity distribution diagram, Gaussian beam intensity distribution diagram and interferometric measurement results when l=1;

[0031] Figure 5 (b) is the relationship between the laser output power and the pump power of this scheme;

[0032] Figure 6 This is a connection diagram of the experimental example of this scheme;

[0033] Figure 7 Schematic diagram of placing a gold film-assisted metasurface on the end face of an optical fiber. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments and the accompanying drawings. Here, the illustrative embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention.

[0035] It should also be noted that, in order to avoid obscuring the present invention due to unnecessary details, only structures and / or processing steps closely related to the solutions according to the present invention are shown in the accompanying drawings, while other details that are not closely related to the present invention are omitted.

[0036] Introduction to existing technology:

[0037] The generation methods of OAM vortex beams can be divided into two categories: extracavity regulation (passive method) and intracavity direct excitation of vortex beams (active method). Extracavity regulation mainly converts Gaussian beams or other forms of beams such as Hermite-Gaussian beams outside the cavity into OAM vortex beams, while intracavity regulation directly generates OAM vortex beams in the laser resonant cavity.

[0038] At first, most of the extracavity control used simple modulation devices such as spiral phase plates and fork-shaped gratings to obtain OAM vortex beams. However, the spiral phase plate has strict requirements on the change of thickness gradient and can only be used in specific bands; although the fork-shaped grating is simple to make and low-cost, its conversion efficiency is not high; with the continuous development of digital customization of light fields, programmable devices such as spatial light modulators have also emerged. In theory, vortex beams of any mode can be flexibly customized through spatial light modulators, but spatial light modulators have shortcomings such as large size, which is not conducive to improving system integration and low efficiency.

[0039] With the rapid development of micro-nano photonics technology, the use of micro-nano optical devices to achieve light field control has become a new research hotspot. Metasurface is an artificially designed two-dimensional planar structure composed of sub-wavelength-scale structural units. It has a high degree of controllability and can finely control the amplitude, phase and polarization of light.

[0040] The existing technology has proposed the concept of metasurface and demonstrated the scheme of generating vortex beams through resonant phase metasurface. Metasurface has the advantages of small size, easy integration and large control freedom.

[0041] Intracavity control is to generate OAM vortex beams directly in the laser resonant cavity by controlling gain and loss or inserting vortex phase modulation devices in the laser resonant cavity. Inserting modulation devices is one of the most common methods of intracavity modulation. The basic principle is to achieve phase control of the beam by inserting modulation devices such as spiral phase plates, variable spiral plates (VSP), spatial light modulators, metasurfaces, etc. in the cavity, so as to output the desired OAM mode. The advantages of intracavity control are: the laser cavity is a natural filter that can be used to eliminate unwanted modes and improve the purity and power of the mode at the same time; the loss associated with external shaping is often not easily overcome, and the loss at the source end can be compensated by increasing the pump power; directly generating OAM vortex beams from the cavity can make the entire system more compact and easy to integrate into other optical components. Prior art 2 combines a multi-task geometric phase metasurface into a laser and uses it as an output coupler to achieve intracavity generation of OAM vortex beams of order 1 to 3. The laser of the third prior art can output a high-purity OAM vortex beam with a topological charge (l) of up to 100, and breaks the symmetry of spin and orbit coupling.

[0042] The vortex lasers introduced above are mostly solid-state lasers. Fiber lasers have the advantages of high gain, good temperature stability and low cost. Prior art four proposes a vortex fiber laser with an adjustable output wavelength of 60nm based on a surface plasmon metasurface. The wavelength adjustable range of this laser is almost twice that of previously reported vortex fiber lasers. In addition, prior art five uses the strong coupling effect of ITO (Indium-Tin-Oxide, ITO) material and metasurface to propose a pulsed vortex fiber laser.

[0043] It is worth mentioning that the metasurfaces in the above-mentioned prior art can only work efficiently in pure reflection or pure transmission mode, which means that they can only effectively manipulate the reflected wavefront or the transmitted wavefront, leaving half of the space unutilized. The full-space metasurface can regulate both the reflection and transmission parts at the same time. Therefore, the research on full-space metasurfaces is of great significance for building highly integrated and compact optical systems. At present, many studies based on full-space metasurfaces have been carried out. Prior art six proposes the use of dielectric metasurfaces to achieve efficient and multifunctional control of visible light in the entire space, which has greatly promoted the research on multifunctional metasurfaces.

[0044] Based on the above background, this paper proposes a gold film-assisted full-space metasurface and a vortex fiber laser based on this metasurface. Compared with the existing vortex fiber laser based on intracavity metasurface, this design can reduce the use of optical devices in the laser cavity, which helps the performance of vortex fiber laser to develop towards miniaturization and lightweight.

[0045] like Figure 1 , Figure 2 , Figure 3 (a) and Figure 3 (b) shows that the present invention proposes a vortex fiber laser based on a gold film-assisted metasurface, wherein the vortex fiber laser based on a gold film-assisted metasurface comprises a pump light source, a wavelength division multiplexer, a collimator and a gold film-assisted metasurface which are sequentially arranged;

[0046] The gold film-assisted metasurface comprises a substrate layer, a gold film layer, a dielectric layer and a nano-unit layer which are sequentially stacked and connected, one side of the substrate layer is close to the collimator, one side of the nano-unit layer is far from the collimator, and the nano-unit layer comprises a plurality of nano-pillars which are evenly arranged;

[0047] In a specific implementation process, the substrate layer and the dielectric layer are made of silicon dioxide, the nanorods are made of amorphous silicon, and the gold film layer is made of gold.

[0048] The pump light source is used to emit laser, and the pump light source is connected to a wavelength division multiplexer, and the wavelength division multiplexer is connected to a collimator through an optical fiber, and the laser is transmitted to the collimator, and the collimator transmits the laser to the gold film-assisted metasurface, and the gold film-assisted metasurface outputs a vortex beam.

[0049] In the specific implementation process, single-mode polarization-maintaining fiber is used to connect various devices in the gold film-assisted metasurface vortex fiber laser.

[0050] By adopting the above scheme, this patent can realize the output of vortex beam with the required topological charge by embedding the full-space metasurface assisted by gold film into the laser cavity. This patent proposes a full-space metasurface assisted by gold film, which can realize a semi-transparent and semi-reflective function. This scheme uses the semi-transparent and semi-reflective function of the gold film to set the gold film on one side of the collimator to complete the reflection. And because the gold film still reflects a Gaussian beam with the same polarization, it is convenient to directly couple the beam back into the laser cavity, and no other devices are required to adjust the polarization, so that the laser oscillates back and forth between the metasurface and the fiber reflector, reducing the use of optical components in the entire system, which is conducive to the further integration of the system; and through the scheme of transmitting the gold film, the adjustment of the beam is completed through the nano-unit layer on the other side to complete the output of the vortex beam.

[0051] In some embodiments of the present invention, the substrate layer and the dielectric layer are made of silicon dioxide, the nanorods are made of amorphous silicon, and the gold film layer is made of gold.

[0052] In some embodiments of the present invention, the thickness of the gold film layer is 8 to 12 nm.

[0053] In a specific implementation process, the thickness of the gold film layer is 10 nm.

[0054] The above scheme is adopted. In this scheme, a metal film is plated on the bottom of the metasurface. The metal film can make the incident light reflect partly and transmit partly, and will not affect the phase of the reflected light and the transmitted light. Since the vortex fiber laser operates in the 1μm band, the metal material used should have a higher reflectivity near this band, such as gold, silver or aluminum. Considering that gold has excellent optical properties, stable structure and advantages in preparation and processing in micro-nano structure design, this scheme adopts gold film for design. After simulation, it is obtained that the optimal value of the gold film thickness that meets the requirements is 10nm. When the incident light passes through the 10nm gold film, the transmitted part passes through the Si nanocolumn to introduce the corresponding phase delay, and the phase control of the transmitted part can be realized.

[0055] like Figure 7 As shown, in some embodiments of the present invention, the gold film-assisted metasurface is disposed on the end face of the optical fiber connected to the output end of the collimator.

[0056] In some embodiments of the present invention, the height of the nanorods is 450-550 nm.

[0057] In a specific implementation process, the height of the nanocolumn is 500 nm.

[0058] In some embodiments of the present invention, the distribution period of the nanorods on the nanounit layer is 440-460 nm.

[0059] In a specific implementation process, the distribution period of the nano-columns on the nano-unit layer is 450 nm.

[0060] In some embodiments of the present invention, the top-view plane of the metasurface is a rectangle, and the rectangle is divided into a plurality of triangular areas by connecting the center of gravity of the rectangle as one end of a ray, and the cumulative phase difference of the X-polarization of the output light of the metasurface in the plurality of triangular areas is 2π.

[0061] like Figure 3 (c) and Figure 3 (d) In some embodiments of the present invention, the metasurface includes 8 triangular regions, and the phase difference of the output light of each triangular region under X-polarized incidence is 0.25π.

[0062] In some embodiments of the present invention, the top-view plane of the gold film-assisted metasurface is a rectangle, and the rectangle is divided into a plurality of triangular areas by connecting the center of gravity of the rectangle as one end of a ray, each triangular area has the same angle at the center of gravity of the rectangle, and the structural parameters of the metasurface units within a single triangular area are the same.

[0063] Using the above scheme, the gold film-assisted metasurface belongs to a transmission phase-type metasurface. Since the Si material has a high refractive index, the truncated waveguide principle can be used to describe the metaatoms. At this time, the nanocolumns are regarded as waveguides truncated up and down, supporting resonant modes with low quality factors, and phase control is achieved through the phase accumulation process of the incident light as a waveguide during propagation.

[0064] In the specific implementation process, the shape and size of the nanorods change, and the equivalent refractive index n of light propagating in the meta-atom eff will change, thus causing the output phase to change, playing a role in phase regulation. Assuming the height of the meta-atom is h, and the wavelength of the incident light in free space is λ0, the phase change can be expressed as:

[0065]

[0066] It can be seen from the above formula that the phase change can be made to cover the range of 0 to 2π by changing the equivalent refractive index.

[0067] Based on the above characteristics, this scheme designs a metasurface suitable for vortex fiber lasers. Table 1 lists the eight metaunits required for the metasurface design, with different geometric parameters. Figure 3 As shown in (c), the transmission phase of the eight meta-units is The size of the nanorods increases gradually, achieving phase coverage from -π to π, and the reflection phase is almost fixed at -π. The transmittance value is about 40%, and the reflectance value is about 60%. Figure 3 (d) By arranging them in sequence, the phase of the transmitted light beam can cover a range from -π to π, satisfying the phase requirement of the OAM vortex light beam with a topological charge number l equal to 1.

[0068] Table 1

[0069] Unit Number Length(nm) Width(nm) 1 200 300 2 230 240 3 230 340 4 350 350 5 160 140 6 150 320 7 170 340 8 200 250

[0070] Scanning Electron Microscopy (SEM) of the gold film-assisted metastructure surface Figure 4 shown.

[0071] In some embodiments of the present invention, the vortex fiber laser based on the gold film-assisted metasurface further includes a lens, which is disposed between the collimator and the gold film-assisted metasurface to shrink the light beam and converge the light beam onto the gold film-assisted metasurface.

[0072] In some embodiments of the present invention, the output end of the vortex fiber laser is connected to another lens to collimate the light beam and output it to the CCD camera.

[0073] In some embodiments of the present invention, the vortex fiber laser based on the gold film-assisted metasurface further includes a fiber reflector, and the fiber reflector is connected to a wavelength division multiplexer.

[0074] like Figure 6 As shown in the figure, in the specific implementation process, the laser with a wavelength of 976nm generated by the pump source is coupled to the laser cavity through a 980 / 1030nm wavelength division multiplexer. In the laser cavity, this solution uses single-mode polarization-maintaining fiber as the gain medium, and uses a collimator to couple the Gaussian beam in the fiber to free space. All devices in the laser need to be connected with single-mode polarization-maintaining fiber to ensure that the output beam is linearly polarized LP 01A mode Gaussian beam is then focused onto the metasurface using a lens with a focal length of f = 50 mm. After the beam passes through the metasurface, it transmits an OAM vortex beam with the same polarization and reflects a Gaussian beam with the same polarization. In this way, the reflected Gaussian beam with the same polarization can be directly coupled back into the laser cavity. This scheme uses a fiber mirror in the cavity so that the laser can oscillate back and forth between the metasurface and the fiber mirror, ultimately forming self-consistent transmission. The beam transmitted from the metasurface is then collimated by a lens with a focal length of f = 50 mm and observed on a CCD camera, and the intensity distribution diagram of the vortex beam can be directly obtained. Figure 5 (a) shows the intensity distribution of the generated OAM vortex beam with l = 1. Figure 5 The white dashed line in (a) is used to mark the Figure 5 It can be seen from (a) that the generated vortex beam has a uniform annular intensity distribution with a dark spot in the center, while the intensity distribution of the reflected part is similar to that of a Gaussian beam, which meets the design requirements of this scheme. At the same time, this scheme measured the transmittance and reflectivity of the metasurface, which were 37% and 39% respectively. This value is consistent with the simulated transmittance (32.4%) and reflectivity (41.3%) obtained by this scheme using the finite difference time domain method (FDTD). In order to further confirm that the beam output by the laser is an OAM vortex beam with l=1, this scheme also conducted a self-interference experiment, and the results are shown in Figure 2. Figure 5 As shown in (a), a fork-shaped stripe is generated, which can confirm that the topological charge of the vortex beam is l = 1. In order to measure the purity of the OAM vortex beam, this scheme uses a lens with a focal length of f = 50mm to focus the OAM vortex beam onto a spatial light modulator loaded with vortex phases of different orders. By measuring the intensity of the central light field, it can be determined that the purity of the OAM vortex beam is 87.8%.

[0075] Figure 5 (b) shows the relationship between the output power of the laser and the pump power, and also presents the spectral characteristics of the output OAM beam in the working state. As the pump power increases to 90mW, the laser begins to oscillate, and the corresponding slope efficiency is 13.8%. Figure 5 (b) It can be seen that the central operating wavelength of the laser is close to 1030nm.

[0076] In summary, this scheme can achieve the output of OAM beams with the required topological charge by embedding the gold film-assisted full-space metasurface into the laser cavity. Compared with the method of generating OAM beams outside the cavity, this design adopts the method of intra-cavity generation, which can improve the purity and power of the mode and make the entire system more compact and efficient. Compared with solid-state lasers, vortex fiber lasers have the advantages of high gain, good temperature stability and low cost. In addition, this scheme proposes a gold film-assisted full-space metasurface, which can realize a semi-transparent and semi-reflective function. Since the gold film still reflects a Gaussian beam with the same polarization, it is convenient to directly couple the beam back into the laser cavity, so that the laser oscillates back and forth between the metasurface and the fiber reflector, reducing the use of optical components in the entire system and facilitating further integration of the system. In addition, due to the unique properties of the gold film-assisted metasurface, it is also possible to further consider directly processing the metasurface on the end face of the optical fiber, such as Figure 7 As shown, the fiber laser that generates a vortex beam in the cavity is made lighter and more compact. Although the experimental results show a vortex fiber laser with a topological charge of l = 1, the metasurface and laser cavity structure design proposed in this scheme are still applicable to other vortex fiber lasers with larger topological charges.

[0077] It should be understood by those skilled in the art that the exemplary components, systems and methods described in conjunction with the embodiments disclosed herein can be implemented in hardware, software or a combination of the two. Whether it is performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention. When implemented in hardware, it can be, for example, an electronic circuit, an application specific integrated circuit (ASIC), appropriate firmware, a plug-in, a function card, etc. When implemented in software, the elements of the present invention are programs or code segments used to perform the required tasks. The program or code segment can be stored in a machine-readable medium, or transmitted on a transmission medium or a communication link via a data signal carried in a carrier.

[0078] It should be clear that the present invention is not limited to the specific configuration and processing described above and shown in the figures. For the sake of simplicity, a detailed description of the known method is omitted here. In the above embodiments, several specific steps are described and shown as examples. However, the method process of the present invention is not limited to the specific steps described and shown, and those skilled in the art can make various changes, modifications and additions, or change the order between the steps after understanding the spirit of the present invention.

[0079] In the present invention, features described and / or illustrated for one embodiment may be used in the same or similar manner in one or more other embodiments, and / or combined with features of other embodiments or replace features of other embodiments.

[0080] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the embodiments of the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A vortex fiber laser based on a gold film-assisted metasurface, characterized in that: The vortex fiber laser based on the gold film-assisted metasurface comprises a pump light source, a wavelength division multiplexer, a collimator and a gold film-assisted metasurface which are arranged in sequence; The gold film-assisted metasurface comprises a substrate layer, a gold film layer, a dielectric layer and a nano-unit layer which are sequentially stacked and connected, one side of the substrate layer is close to the collimator, one side of the nano-unit layer is far from the collimator, and the nano-unit layer comprises a plurality of nano-pillars which are evenly arranged; The pump light source is used to emit laser, and the pump light source is connected to a wavelength division multiplexer, and the wavelength division multiplexer is connected to a collimator through an optical fiber, and the laser is transmitted to the collimator, and the collimator transmits the laser to the gold film-assisted metasurface, and the gold film-assisted metasurface outputs a vortex beam.

2. The vortex fiber laser based on gold film-assisted metasurface according to claim 1, characterized in that: The substrate layer and the dielectric layer are made of silicon dioxide, the nanocolumns are made of amorphous silicon, and the gold film layer is made of gold.

3. The vortex fiber laser based on gold film-assisted metasurface according to claim 1, characterized in that: The thickness of the gold film layer is 8-12 nm.

4. The vortex fiber laser based on gold film-assisted metasurface according to claim 1, characterized in that: The height of the nanocolumn is 450-550 nm.

5. The vortex fiber laser based on gold film-assisted metasurface according to claim 1, characterized in that: The gold film-assisted metasurface is arranged on the end face of the optical fiber connected to the output end of the collimator.

6. The vortex fiber laser based on gold film-assisted metasurface according to claim 1, characterized in that: The top-view plane of the metasurface is a rectangle, and the rectangle is divided into a plurality of triangular regions by connecting the center of gravity of the rectangle as one end of a ray. The accumulated phase difference of the X-polarization of the output light of the metasurface in the plurality of triangular regions is 2π.

7. The vortex fiber laser based on gold film-assisted metasurface according to claim 1, characterized in that: The metasurface includes 8 triangular regions, and the phase difference of the output light of each triangular region under X-polarization incidence is 0.25π.

8. The vortex fiber laser based on gold film-assisted metasurface according to claim 1, characterized in that: The angles of the corners of each triangular region at the position of the center of gravity of the rectangle are the same, and the structural parameters of the metasurface units within a single triangular region are the same.

9. The vortex fiber laser based on gold film-assisted metasurface according to claim 1, characterized in that: The vortex fiber laser based on the gold film-assisted metasurface also includes a lens, which is arranged between the collimator and the gold film-assisted metasurface to shrink the light beam and converge the light beam on the gold film-assisted metasurface.

10. The vortex fiber laser based on gold film-assisted metasurface according to claim 9, characterized in that: The vortex fiber laser based on the gold film-assisted metasurface also includes a fiber reflector, which is connected to the wavelength division multiplexer.

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