A vortex fiber laser based on a full-space all-dielectric metasurface

Abstract

The present invention provides a vortex fiber laser based on a full-space all-dielectric metasurface, comprising a pump light source, a wavelength division multiplexer, a collimator, a Faraday rotator and a full-space all-dielectric metasurface which are arranged in sequence; the pump light source is used to emit laser light, the pump light source is connected to the wavelength division multiplexer, the wavelength division multiplexer is connected to the collimator through an optical fiber, the laser light is transmitted to the collimator, the collimator transmits the laser light to the Faraday rotator, the Faraday rotator outputs a 45° polarized light beam to the full-space all-dielectric metasurface, and the metasurface outputs a vortex light beam; the metasurface is uniformly provided with a plurality of metasurface units, each of the metasurface units comprises two nanocolumns, the y-polarized phase difference of the output light of the two nanocolumns of the metasurface unit is equal to a first set value, and the phase difference cumulative value of the output light of the metasurface unit of the metasurface under x-polarized incidence is a second set value.

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 full-space all-dielectric metasurface. Background Art

[0002] In recent years, vortex beams have attracted widespread attention due to their orbital angular momentum (OAM). The notable feature of vortex beams is that they have a spiral phase that is related to the azimuth and helicity. In the field of optical communications, the topological protection and state-unbounded characteristics of OAM beams add new degrees of freedom to information encoding, which can significantly improve the capacity and spectral efficiency of optical communication systems, especially under the constraints of limited spatial bandwidth of optical channels. In the field of optical tweezers, vortex beams have great potential in the field of optical tweezers because the central light intensity is theoretically close to zero, and even when focused, it is not easy to cause thermal damage to the trapped particles, and it is not easily affected by the relative refractive index of the trapped particles.

[0003] The methods of generating vortex beams are often divided into generating vortex beams inside the cavity and generating vortex beams outside the cavity. The spiral phase plate is one of the most important methods for generating vortex beams outside the cavity. The spiral phase plate has a spiral internal structure, which can convert the incident Gaussian beam into a vortex beam. The topological charge of the generated vortex beam is determined by the specific structure inside the spiral phase plate. The spiral phase plate has the advantages of high precision and high efficiency. Other methods for generating vortex beams outside the cavity include variable vortex plates, spatial light modulators, etc. However, vortex beams generated outside the cavity often have many limitations, such as low purity and poor conversion efficiency. [1] Therefore, the generation of active vortex beams has become one of the research hotspots. The intracavity generation of vortex beams mainly includes solid-state lasers and fiber lasers.

[0004] However, since traditional metasurfaces can only affect the reflection or transmission areas, existing lasers usually need to use polarization beam splitters to separate the Gaussian beam and the vortex beam, which takes up additional space and makes the entire laser cavity less compact. Summary of the invention

[0005] In view of this, an embodiment of the present invention provides a vortex fiber laser based on a full-space all-dielectric 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 full-space all-dielectric metasurface, wherein the vortex fiber laser based on the full-space all-dielectric metasurface comprises a pump light source, a wavelength division multiplexer, a collimator, a Faraday rotator and a full-space all-dielectric metasurface arranged in sequence;

[0007] The pump light source is used to emit laser light, the pump light source is connected to a wavelength division multiplexer, the wavelength division multiplexer is connected to a collimator through an optical fiber, the laser light is transmitted to the collimator, the collimator transmits the laser light to a Faraday rotator, the Faraday rotator converts a 67.5° polarized light beam output by the collimator into a 45° polarized light beam, and the metasurface outputs a vortex light beam;

[0008] The metasurface is evenly provided with a plurality of metasurface units, each of the metasurface units includes two nanocolumns, the y-polarized phase difference of the output light of the two nanocolumns of the metasurface unit is a first set value, and the phase difference cumulative value of the output light of the metasurface unit of the metasurface under x-polarized incidence is a second set value.

[0009] By adopting the above scheme, the patent designs a laser based on an all-dielectric all-space metasurface, which can realize asymmetric transmission according to the polarization state of the incident light. Since the phase difference cumulative value of the output light of the metasurface unit of the metasurface under x-polarization incidence is a second set value, a vortex beam is transmitted under the incidence of an x-polarized light beam (the polarization states x and y of the light beam are defined according to the structural direction of the metasurface unit). Since the y-polarization phase difference of the output light of the two nanocolumns of the metasurface unit is a first set value, an induced reflection is generated under the incidence of a cross-polarized (y-polarized) light beam, and the metasurface is transformed into a reflective metasurface, reflecting a Gaussian beam, completing the separation of the Gaussian beam and the vortex beam, and being able to directly emit the vortex beam. The structure of this scheme can simultaneously assume the functions of one end of the laser cavity (the reflected Gaussian beam will be coupled back into the cavity to generate oscillation) and the output end of the vortex beam.

[0010] 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, each triangular area has the same angle at the center of gravity of the rectangle, and the structural parameters of the metasurface unit of each triangular area are the same.

[0011] In some embodiments of the present invention, the top-view plane of the metasurface unit is a rectangle composed of two squares of the same area, and in the top-view plane of the metasurface unit, two nanocolumns are respectively within the range of the two squares, and the center of gravity of the rectangle formed by the nanocolumns is the same as the center of gravity of the squares.

[0012] In some embodiments of the present invention, the first set value is π, and the phase difference of the y-polarization of the output light of the two nanorods of the metasurface unit is π.

[0013] In some embodiments of the present invention, the second set value is 2π, and the accumulated phase difference of the output light of the metasurface unit of the metasurface under x-polarization incidence is 2π.

[0014] In some embodiments of the present invention, the top-view plane of the metasurface is a rectangle, and the rectangle is divided into 8 triangular areas by connecting the center of gravity of the rectangle as one end of a ray, and the phase difference of the output light under x-polarization incidence in each triangular area is 0.25π.

[0015] In some embodiments of the present invention, the vortex fiber laser based on the full-space all-dielectric metasurface further includes a first lens and a second lens, wherein the first lens is disposed between the Faraday rotator and the full-space all-dielectric metasurface to shrink the light beam and converge the light beam on the metasurface; the second lens is disposed at the output end of the full-space all-dielectric metasurface to collimate the light beam, and the second lens is disposed outside the laser cavity.

[0016] In some embodiments of the present invention, the vortex fiber laser based on the full-space all-dielectric metasurface further includes a fiber reflector, and the fiber reflector is connected to a wavelength division multiplexer.

[0017] In some embodiments of the present invention, the metasurface unit further includes a base plate, and the two nanopillars are connected to the base plate.

[0018] In some embodiments of the present invention, the base plate is made of silicon dioxide, and the nanorods are made of amorphous silicon.

[0019] In some embodiments of the present invention, the height of the nanorods is 500 nm.

[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 1A schematic diagram of an embodiment of a vortex fiber laser based on a full-space all-dielectric metasurface of the present invention;

[0024] Figure 2 It is a schematic diagram of the connection structure of the experimental example of the present invention;

[0025] Figure 3 The simulation results of the metasurface unit under x-polarized and y-polarized light incident;

[0026] Figure 4 The simulation results of the metasurface under the incidence of 45° linearly polarized Gaussian beam;

[0027] Figure 5 Schematic diagram of metasurface unit and its arrangement. DETAILED DESCRIPTION

[0028] 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.

[0029] 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.

[0030] like Figure 1 As shown, the present invention proposes a vortex fiber laser based on a full-space all-dielectric metasurface, wherein the vortex fiber laser based on the full-space all-dielectric metasurface comprises a pump light source, a wavelength division multiplexer, a collimator, a Faraday rotator and a full-space all-dielectric metasurface which are sequentially arranged;

[0031] The pump light source is used to emit laser light, the pump light source is connected to a wavelength division multiplexer, the wavelength division multiplexer is connected to a collimator through an optical fiber, the laser light is transmitted to the collimator, the collimator emits laser light, the function of the Faraday rotator is to change the polarization state of the light beam, convert the 67.5° polarized light input by the collimator into 45°, change the y-polarized light beam output by the metasurface into 67.5 degrees and couple it back to the collimator, the metasurface outputs a vortex light beam;

[0032] In the specific implementation process, the connection between the various components in the vortex fiber laser adopts polarization-maintaining single-mode fiber to ensure that the light beam in the fiber optical path is linearly polarized LP 01 mold.

[0033] In the specific implementation process, the 976nm pump light is injected into the resonant cavity through a 980 / 1030nm wavelength division multiplexer. The Yb-doped polarization-maintaining fiber is used as the gain medium. The linearly polarized light beam output by the collimator has a polarization angle of 67.5° relative to the x-axis (the x-axis is defined in Figure 1 ), and is converted into linearly polarized light at 45° after passing through a 22.5° Faraday rotator.

[0034] The metasurface is evenly provided with a plurality of metasurface units, each of the metasurface units includes two nanocolumns, the y-polarized phase difference of the output light of the two nanocolumns of the metasurface unit is a first set value, and the phase difference cumulative value of the output light of the metasurface unit of the metasurface under x-polarized incidence is a second set value.

[0035] By adopting the above scheme, the patent designs a laser based on an all-dielectric all-space metasurface, which can realize asymmetric transmission according to the polarization state of the incident light. Since the phase difference cumulative value of the output light of the metasurface unit of the metasurface under x-polarization incidence is a second set value, a vortex beam is transmitted under the incidence of an x-polarized beam (the polarization states x and y of the beam are defined according to the structural direction of the metasurface unit). Since the y-polarization phase difference of the output light of the two nanocolumns of the metasurface unit is a first set value, an induced reflection is generated under the incidence of a cross-polarized (y-polarized) beam, and the metasurface is transformed into a reflective metasurface, reflecting a Gaussian beam, completing the separation of the Gaussian beam and the vortex beam, and being able to directly emit the vortex beam. The metasurface structure of this scheme can simultaneously assume the functions of one end of the laser cavity (the reflected Gaussian beam will be coupled back into the cavity to generate oscillation) and the output end of the vortex beam.

[0036] 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, each triangular area has the same angle at the center of gravity of the rectangle, and the structural parameters of the metasurface unit of each triangular area are the same.

[0037] In some embodiments of the present invention, the top-view plane of the metasurface unit is a rectangle composed of two squares of the same area, and in the top-view plane of the metasurface unit, two nanocolumns are respectively within the range of the two squares, and the center of gravity of the rectangle formed by the nanocolumns is the same as the center of gravity of the squares.

[0038] In some embodiments of the present invention, the first set value is π, and the phase difference of the y-polarization of the output light of the two nanorods of the metasurface unit is π.

[0039] In some embodiments of the present invention, the second set value is 2π, and the accumulated phase difference of the output light of the metasurface unit of the metasurface under x-polarization incidence is 2π.

[0040] like Figure 5 As shown in (d), in some embodiments of the present invention, the top-view plane of the metasurface is a rectangle, and the rectangle is divided into 8 triangular areas by connecting the center of gravity of the rectangle as one end of a ray, and the phase difference of the output light of each triangular area under x-polarization incidence is 0.25π.

[0041] In some embodiments of the present invention, the vortex fiber laser based on the full-space all-dielectric metasurface further includes a first lens and a second lens, wherein the first lens is disposed between the Faraday rotator and the full-space all-dielectric metasurface to shrink the light beam and converge the light beam on the metasurface; the second lens is disposed at the output end of the full-space all-dielectric metasurface to collimate the light beam, and the second lens is disposed outside the laser cavity.

[0042] Figure 1 and 2 The lens 1 and lens 2 in the figure correspond to the first lens and the second lens respectively.

[0043] In some embodiments of the present invention, the vortex fiber laser based on the full-space all-dielectric metasurface further includes a fiber reflector, and the fiber reflector is connected to a wavelength division multiplexer.

[0044] In the specific implementation process, the OAM beam of the x-polarization component is emitted from the output end, the Gaussian beam of the y-polarization component is reflected by the metasurface, and converted into 67.5° linear polarized light by the Faraday rotator, and finally coupled back into the collimator. The fiber reflector and the metasurface serve as the two ends of the laser cavity to ensure that the Gaussian beam can oscillate back and forth in the linear cavity. Therefore, the transverse intensity distribution and polarization state characteristics of the beam can form self-consistent transmission in the cavity, and the polarization-maintaining gain fiber and related optical elements ensure that the laser emission is around 1030nm, corresponding to the design wavelength of the metasurface.

[0045] In some embodiments of the present invention, the metasurface unit further includes a base plate, and the two nanopillars are connected to the base plate.

[0046] In some embodiments of the present invention, the base plate is made of silicon dioxide, and the nanorods are made of amorphous silicon.

[0047] In some embodiments of the present invention, the height of the nanorods is 500 nm.

[0048] In the specific implementation process, the optical metasurface is an optical element composed of sub-wavelength artificial atoms. Compared with traditional optical elements, the metasurface has the advantages of extremely thin thickness and extremely low weight. The metasurface can modulate the amplitude, phase and polarization of the incident light beam at the same time with low loss.

[0049] In the specific implementation process, the principle of the metasurface designed in this scheme is based on the anomalous diffraction of induced reflection. Assuming a periodic metaatomic array with a phase gradient of ξ, the state of the output light can usually be described by the generalized Snell's law (GSL), that is, k out =k in +ξ, where k out and k in are the transverse momentum of the outgoing light and the incident light, respectively, and ξ is the phase gradient between the meta-units. However, when the phase gradient is greater than the wave vector in free space, GSL will not apply to this meta-surface. This condition is called the critical angle condition, and the formula describing the outgoing light field needs to be replaced by K out =k in +ξ+(n-1)G; This formula is the diffraction law of parity inversion. In this formula, n represents the diffraction order of the outgoing light field, and G is the reciprocal lattice vector of the metasurface unit structure, which is usually equivalent to ξ in value.

[0050] If the number of times light propagates back and forth in a meta-unit is set to δ, then δ can be expressed as δ=m+n, where m represents the number of nanopillars in a meta-unit. When the number of nanopillars contained in the basic unit of the metasurface is 2, such as Figure 5 As shown in (c), as long as the critical condition is met, direct transmission cannot occur (δ=1), but reflection is induced (δ=2), and the reflected light accounts for the vast majority of the energy.

[0051] Experimental example

[0052] The experimental example of a vortex fiber laser based on a full-space all-dielectric metasurface connected to a CCD camera

[0053] Based on the above characteristics, the basic unit of the metasurface in this scheme is composed of SiO 2 It consists of two amorphous silicon nanorods on a substrate. Figure 5 As shown in (a) and (b), Figure 5(a), (b) and (c) are schematic diagrams of the structure of the metasurface unit. The length (L) and width (W) of each nanocolumn are adjustable, and the height is uniformly set to H = 500nm. The period of a single nanocolumn is P = 450nm. Amorphous silicon has a high refractive index and low absorptivity at the operating wavelength (1030nm), so this metasurface usually behaves as a transmissive metasurface. When y-polarized light is incident on the metasurface, the critical angle condition is broken and the metasurface exhibits the characteristics of a reflective metasurface. Due to the birefringence of amorphous silicon nanocolumns, each basic unit of the metasurface can independently adjust the phase of reflection and transmission. According to the requirements of the vortex laser, the metasurface needs to exhibit the characteristics of mirror reflection when y-polarized light is incident, and at the same time, it can output a vortex beam when x-polarized light is incident. The length and width of the silicon nanopillars were scanned step by step at 1030 nm using the finite difference time domain method (FDTD), and 8 groups of nanopillars were finally selected. The specific geometric parameters are shown in Table 1. Table 1 records the specific structural parameters of the 8 groups of nanopillars. The phase relationship design satisfies as well as in represents the phase of x-polarized incident on a nanorod in the same metasurface unit, represents the phase of another nanorod in the same metasurface unit with x-polarization incident on it; represents the phase of the y-polarized incident nanorod in the same metasurface unit, represents the phase of another nanorod in the same metasurface unit under y-polarized incident. The transmittance or reflectivity and phase delay of the selected nanorod under x- or y-polarized incident are shown in Figure 3 (a) and 3(b), Figure 3 (a) Schematic diagram of transmittance and transmission phase of 8 meta-units when x-polarized light is incident at a wavelength of 1030 nm; Figure 3 (b) Schematic diagram of the reflectivity and reflection phase of 8 meta-units under y-polarized light with a wavelength of 1030nm. For x-polarized light, the diffraction mechanism of the output light follows GSL. Phase shift of the transmitted light Almost equal to and A high transmittance greater than 0.85 is obtained. For y-polarized incidence, since the critical angle condition is satisfied Most of the light field is reflected. At the same time, for these 8 groups of nanounits, when y-polarized incident light is incident, the reflection phases are guaranteed to be close to the same, provided that the critical angle condition is met. When x-polarized incident light is incident, the reflection phases are guaranteed to be close to the same, provided that the critical angle condition is met. Under the premise of , the transmission phase between each group differs by π / 4.

[0054] Table 1

[0055] Unit Number <![CDATA[Nano-column L 1 Length (nm)]]> <![CDATA[Nano-column W 1 Width (nm)]]> <![CDATA[Nano-pillar L 2 Length (nm)]]> <![CDATA[Nano-column W 2 Width (nm)]]> 1 170 215 150 350 2 200 200 170 320 3 220 195 185 315 4 235 190 200 290 5 260 185 225 270 6 310 175 250 265 7 350 170 290 250 8 130 230 145 355

[0056] according to Figure 5 (d) The arrangement of Figure 5 (d) is a schematic diagram of the distribution of metasurface units on the metasurface. These eight groups of nanounits are arranged so that when y-polarized light is incident on the metasurface, the phase and amplitude of the reflected light are almost the same fixed value, ensuring that the reflected light beam is as close to the Gaussian light beam as possible. When x-polarized light is incident, the phase of the transmitted light beam increases by π / 4 successively, so that the change in the light beam phase accumulates to 2π, thereby outputting an OAM light beam with a topological charge of 1.

[0057] The present invention simulates the far-field distribution of transmission and reflection of a metasurface under 45° linearly polarized light incidence. Figure 4 shows the output of the metasurface, Figure 4 (a) is the intensity distribution diagram of the reflected beam; Figure 4 (b) Vortex light intensity distribution diagram when the transmitted topological charge is 1; Figure 4 (c) Phase distribution diagram of reflected beam; Figure 4 (d) Phase distribution of the vortex beam with a topological charge of 1. The intensity at the center of the transmitted light field is close to 0, and the phase distribution is basically consistent with the OAM beam with a topological charge of 1. At the same time, the reflected light field is almost a perfect Gaussian beam. The transmittance and reflectivity are close, 45.3% and 41.2% respectively, which meets the design goal.

[0058] This patent realizes a compact vortex fiber laser by embedding a full-space metasurface into the laser cavity. The laser consists of multiple key components, including a 976nm laser pump source, a polarization-maintaining ytterbium-doped fiber, a metasurface, a 22.5° Faraday rotator, and other standard optical elements. Through clever optical path design, we have utilized the anomalous diffraction phenomenon of the metasurface inside the fiber laser for the first time, providing a novel method for directly emitting vortex beams through fiber lasers. The high gain and mode filtering mechanism of the fiber laser cavity and the multifunctionality and high degree of freedom of the metasurface make it possible for the laser cavity to directly output high-purity and high-power vortex beams. At the same time, due to the high degree of freedom of the metasurface, the design concept of the proposed fiber laser has commonality. For example, similar laser cavities can be used to output vortex beams with other topological charges or other scalar structure beams that can be obtained through phase control. All that needs to be changed is the structural arrangement of the eight groups of nanocolumns. At the same time, similar design methods can not only be used for the operating wavelength of ytterbium-doped fiber lasers, but can also be applied to fiber lasers with other operating wavelengths, such as erbium-doped fiber lasers, etc.

[0059] Using the above scheme, the present invention proposes a vortex fiber laser based on an all-dielectric full-space metasurface. This scheme uses the full-space metasurface to directly output a vortex beam in a compact and simple laser cavity. The metasurface is reasonably designed, and the degree of freedom of the metasurface to manipulate the light beam is introduced from a single side into the full space by using anomalous diffraction, so that the metasurface has the function of reflecting Gaussian beams and transmitting vortex beams at the same time according to the polarization state of the incident light. This scheme provides a novel method for fiber lasers to directly emit vortex beams, expands the design of vortex lasers, and can become an ideal light source in the fields of optical communications, optical tweezers, and special processing.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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 full-space all-dielectric metasurface, characterized in that: The vortex fiber laser based on the full-space all-dielectric metasurface comprises a pump light source, a wavelength division multiplexer, a collimator, a Faraday rotator and a full-space all-dielectric metasurface which are arranged in sequence; The pump light source is used to emit laser light, the pump light source is connected to a wavelength division multiplexer, the wavelength division multiplexer is connected to a collimator through an optical fiber, the laser light is transmitted to the collimator, the collimator transmits the laser light to a Faraday rotator, the Faraday rotator outputs a 45° polarized light beam to the full-space all-dielectric metasurface, and the metasurface outputs a vortex light beam; 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, the angle of each triangular area at the center of gravity of the rectangle is the same, and the structural parameters of the metasurface unit of each triangular area are the same; the metasurface is evenly provided with a plurality of metasurface units, each of the metasurface units includes two nanocolumns, the phase difference of the output light of the two nanocolumns of the metasurface unit under y-polarization incidence is equal to a first set value, and the accumulated value of the phase difference of the output light of the metasurface unit of the metasurface under x-polarization incidence is a second set value; the top-view plane of the metasurface unit is a rectangle composed of two squares of the same area, and the two nanocolumns are respectively within the range of the two squares in the top-view plane of the metasurface unit, and the center of gravity of the rectangle composed of the nanocolumns is the same as the center of gravity of the square.

2. The vortex fiber laser based on the full-space all-dielectric metasurface according to claim 1 is characterized in that: The first set value is π, and the phase difference of the y-polarization of the output light of the two nanorods of the metasurface unit is equal to π.

3. The vortex fiber laser based on the full-space all-dielectric metasurface according to claim 1 is characterized in that: The second set value is 2π, and the phase difference accumulation value of the output light of the metasurface unit of the metasurface under x-polarization incidence is 2π.

4. The vortex fiber laser based on the full-space all-dielectric metasurface according to claim 2, characterized in that: The top-view plane of the metasurface is a rectangle, and the rectangle is divided into 8 triangular areas by connecting the center of gravity of the rectangle as one end of a ray. The phase difference of the output light of each triangular area under x-polarization incidence is 0.25π.

5. The vortex fiber laser based on the full-space all-dielectric metasurface according to claim 1, characterized in that: The vortex fiber laser based on the full-space all-dielectric metasurface also includes a first lens and a second lens. The first lens is arranged between the Faraday rotator and the full-space all-dielectric metasurface to shrink the light beam and converge the light beam on the metasurface. The second lens is arranged at the output end of the full-space all-dielectric metasurface to collimate the light beam. The second lens is arranged outside the laser cavity.

6. The vortex fiber laser based on the full-space all-dielectric metasurface according to claim 1, characterized in that: The vortex fiber laser based on the full-space all-dielectric metasurface also includes a fiber reflector, which is connected to the wavelength division multiplexer.

7. The vortex fiber laser based on the full-space all-dielectric metasurface according to claim 1, characterized in that: The metasurface unit further includes a base plate, and the two nanopillars are connected to the base plate.

8. The vortex fiber laser based on the full-space all-dielectric metasurface according to claim 7, characterized in that: The base plate is made of silicon dioxide, and the nanorods are made of amorphous silicon.

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