All-fiber space-time mode-locked vortex light generation method based on metasurface

Abstract

The invention provides a metasurface-based all-fiber space-time mode-locked pulse vortex light generation method. A laser comprises a single-mode pump, a multi-mode wavelength division multiplexer, a multi-mode isolator, a metasurface saturable absorber, a first multi-mode polarization controller, a multi-mode fiber coupler and a second multi-mode polarization controller which are sequentially connected through multi-mode fibers. Wherein the multi-mode optical fiber coupler and the second multi-mode polarization controller are combined to form an output unit of the laser, the multi-mode optical fiber coupler is used for laser output, and the second multi-mode polarization controller is used for state adjustment of output vortex light beams; the metasurface saturable absorber adopts an integrated form of a metasurface and a multimode optical fiber patch cord, and is used for space-time mode locking and vortex beam generation. The controllable metasurface structure and the multimode optical fiber are combined, pulse output is achieved on the basis of the space-time mode-locked laser, pulse vortex light beam output is obtained through metasurface structure design, and an effective technical means is provided for achieving high-dimension optical information processing and quantum communication.

Description

(I) Technical field

[0001] The present invention relates to the field of laser technology, and in particular to a method for generating all-fiber spatiotemporal mode-locked vortex light based on a metasurface. (II) Background technology

[0002] As an optical element precisely designed and manufactured at the micrometer or nanometer scale, metasurfaces can achieve efficient control of light wavefronts and propagation directions. Based on multimode fiber lasers, based on the characteristics of spatial mode locking and high temporal correlation, metasurface tilted gratings designed on the end face of multimode optical fibers can produce a specific refractive index distribution inside the optical fiber, thereby achieving mode selection and control, and further realizing the generation of ultrafast vortex pulses. The all-fiber spatiotemporally mode-locked vortex optical laser based on metasurface tilted gratings has the advantages of simple structure, small size, high flexibility and strong controllability, providing an effective technical means for realizing high-dimensional optical information processing and quantum communication, and achieving higher pulse energy, better beam quality and wider application potential. (III) Summary of the invention

[0003] In view of this, the purpose of the present invention is to provide a method for realizing an all-fiber space-time mode-locked pulsed vortex beam based on a metasurface, which has a small size, simple structure, high flexibility and can achieve precise control of the topological charge of the vortex beam.

[0004] In the first aspect, an embodiment of the present invention provides a method for generating all-fiber spatiotemporal mode-locked vortex light based on a metasurface, comprising: a single-mode pump, a multi-mode wavelength division multiplexer, a few-mode erbium-doped fiber, a multi-mode isolator, a first multi-mode polarization controller, a metasurface saturable absorber, a multi-mode output coupler, and a second multi-mode polarization controller connected in sequence through optical fibers; wherein the single-mode pump is used to obtain pump light; the multi-mode wavelength division multiplexer is used to couple the pump light with the signal light; the few-mode gain fiber is used to excite the pump light; the multi-mode isolator is used to ensure the unidirectionality of laser operation; the first multi-mode polarization controller is used to adjust the polarization state in the resonant cavity; the metasurface saturable absorber is used to realize the generation of a pulsed vortex beam; the multi-mode output coupler is used to output the above-mentioned pulsed vortex laser to form an all-fiber ring structure; and the second multi-mode polarization controller is used to adjust the output state of the vortex beam.

[0005] In combination with the first aspect, an embodiment of the present invention provides a first possible implementation of the first aspect, wherein the above-mentioned metasurface saturable absorber adopts a metasurface structure prepared on the end face of a multimode optical fiber to achieve the output of all-fiber space-time mode-locked pulses.

[0006] In combination with the first aspect, an embodiment of the present invention provides a second possible implementation method of the first aspect, wherein the above-mentioned metasurface saturable absorber includes structures such as nanorods, nanoeyes, nanorings, nanoblocks, tilted gratings, etc., and precise control of the topological charge of the vortex light beam is achieved by adjusting the design and arrangement parameters of the metasurface.

[0007] In combination with the first aspect, an example of the present invention provides a third possible implementation of the first aspect, wherein the above-mentioned first multimode polarization controller is used to adjust the angle of the input light of the metasurface multimode optical fiber to achieve light beam control.

[0008] In combination with the first aspect, an example of the present invention provides a fourth possible implementation of the first aspect, wherein the above-mentioned laser output unit includes a multimode coupler and a second multimode polarization controller, the multimode coupler is used for pulsed vortex beam output, and the second multimode polarization controller is used for adjusting the output state of the pulsed vortex beam.

[0009] The embodiments of the present invention bring the following beneficial effects:

[0010] The embodiment of the present invention provides a method for generating an all-fiber spatiotemporal mode-locked vortex beam based on a metasurface, using a metasurface structure as a saturable absorber in a multimode fiber laser to achieve ultrafast pulse generation, and adopts a method of adjusting the design parameters of the metasurface structure to achieve precise control of vortex beam generation and topological charge number. The multimode fiber laser is composed of a single-mode pump light, a multimode wavelength division multiplexer, a few-mode erbium-doped fiber, a multimode isolator, a first multimode polarization controller, a metasurface saturable absorber, and a multimode coupler. The output state of the vortex beam is adjusted by using a second multimode polarization controller at the output end.

[0011] The metasurface-based vortex beam control method provided in the embodiment of the present invention uses a large-core multimode optical fiber as a substrate, and prepares the metasurface structure on the end face of the optical fiber, which can realize the output of all-fiber spatiotemporal mode-locked pulsed vortex beams in multimode fiber lasers. Compared with the prior art, the example of the present invention realizes the simultaneous output of spatiotemporal mode-locked pulses and vortex beams, which improves the pulse output energy and increases the polarization and phase information of the beam. Combining the advantages of metasurface technology and spatiotemporal mode-locking technology, it provides a new way for high-dimensional optical information encoding and transmission.

[0012] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention are realized and obtained by the structures particularly pointed out in the description, claims and drawings.

[0013] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. (IV) Description of the drawings

[0014] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0015] Figure 1 A schematic diagram of the structure of a method for generating an all-fiber spatiotemporal mode-locked vortex beam based on a metasurface provided in an embodiment of the present invention;

[0016] Figure 2 A schematic diagram of the structure of a multimode optical fiber metasurface saturable absorber provided in an embodiment of the present invention;

[0017] icon:

[0018] 110-single-mode pump; 120-multimode wavelength division multiplexer; 130-few-mode gain fiber; 140-multimode isolator; 150-first u-multimode polarization controller; 160-multimode coupler; 170-second multimode polarization controller; 200-metasurface saturable absorber; 210-multimode fiber jumper head; 220-multimode fiber jumper end face; 221-multimode fiber core; 222-multimode fiber cladding; 223-metasurface structure example. (V) Specific implementation methods

[0019] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] The present invention provides a method for generating a space-time mode-locked pulse vortex beam in an all-fiber structure based on a metasurface. The method has the advantages of simple structure, high integration, high degree of freedom, and strong adjustability. The method can realize the output of a space-time mode-locked pulse vortex beam by adjusting the design parameters of the metasurface in an all-fiber structure, and can precisely control the topological charge of the vortex beam, thus providing a new solution for high-dimensional optical information processing and quantum communication.

[0021] To facilitate understanding of this embodiment, firstly, a method for generating an all-fiber spatiotemporal mode-locked vortex beam based on a metasurface disclosed in an embodiment of the present invention is described in detail, see Figure 1A schematic diagram of an all-fiber spatiotemporal mode-locked vortex beam laser based on a metasurface is shown, the laser comprising: a single-mode pump 110, a multi-mode wavelength division multiplexer 120, a few-mode gain fiber 130, a multi-mode isolator 140, a metasurface saturable absorber 200, a first multi-mode polarization controller 150, a multi-mode coupler 160, and a second multi-mode polarization controller 170 connected in sequence through optical fibers.

[0022] The single-mode pump 110 is used to output pump light.

[0023] The multimode wavelength division multiplexer 120 is used to couple the pump light and the signal light output by the pump into the multimode optical fiber.

[0024] The few-mode gain fiber 130 is used for absorbing and exciting the pump light to generate signal light.

[0025] The multimode isolator 140 is used to ensure the unidirectionality of laser operation.

[0026] The metasurface saturable absorber 200 is used for beam modulation to generate a pulsed vortex beam.

[0027] The first multimode polarization controller 150 is used to adjust the polarization state of the light beam in the resonant cavity.

[0028] The multimode fiber coupler 160 is used to obtain ultrafast pulse laser based on the signal light and output the ultrafast pulse laser. Specifically, one end is connected to a mode-locking device to maintain the normal operation of the laser, and the other end outputs the ultrafast pulse laser.

[0029] The second multi-mode polarization controller 170 is used to adjust the output state of the pulsed vortex beam.

[0030] The embodiment of the present invention provides a method for generating a spatiotemporal mode-locked pulsed vortex beam based on an all-fiber structure of a metasurface, including a single-mode pump, a multi-mode wavelength division multiplexer, a few-mode gain fiber, a multi-mode isolator, a metasurface saturable absorber, a first multi-mode polarization controller, a multi-mode coupler, and a second multi-mode polarization controller connected in sequence through optical fibers. Specifically, the single-mode pump outputs pump light, which is coupled into the few-mode gain fiber through the wavelength division multiplexer, the multi-mode isolator ensures the unidirectional transmission of the laser, the metasurface saturable absorber is used for mode locking and phase adjustment, the first polarization controller is used to adjust the polarization state of the light beam in the resonant cavity, and the multi-mode coupler separates the light beam in a ratio of 20:80, 80% of the light continues to enter the resonant cavity to maintain the operation of the laser, and 20% of the light beam outputs the laser cavity, and the output light beam state is adjusted by the second polarization controller. The method for generating a spatiotemporal mode-locked vortex beam provided by the example of the present invention not only realizes a high-integration, high-stability output, but also can adjust the topological charge of the vortex beam according to the design of the metasurface structure, providing an effective technical means for realizing high-dimensional optical information processing and quantum communication.

[0031] In order to facilitate the understanding of the method for generating a spatiotemporal mode-locked pulsed vortex beam based on an all-fiber structure of a metasurface provided in the above embodiment, the present invention also provides a reference Figure 2 The structure schematic diagram of the metasurface saturable absorber shown in the figure includes: a multimode fiber jumper 210, a multimode fiber end face metasurface structure 220, a multimode fiber core 221, a multimode fiber cladding 222, and a metasurface structure 223.

[0032] The multimode fiber jumper 210 is used as the supporting substrate of the metasurface to realize a pulsed vortex beam of an all-fiber structure.

[0033] The metasurface 220 on the end face of the multimode optical fiber is used for beam conditioning.

[0034] The multimode optical fiber core 221 is used for signal light transmission.

[0035] The multimode optical fiber cladding 222 is used to function as an optical waveguide, limiting the propagation path of light inside the fiber core.

[0036] The metasurface structure 223 is used for beam adjustment, and the topological charge of the vortex beam is adjusted through the structural design of the metasurface.

[0037] In summary, the embodiment of the present invention provides a method for generating a pulsed vortex beam based on a metasurface-based all-fiber structure with spatiotemporal mode-locking, which uses a spatiotemporal mode-locked laser structure based on a multimode fiber, including a single-mode pump, a multimode wavelength division multiplexer, a few-mode gain fiber, a multimode isolator, a metasurface saturable absorber, a multimode polarization controller, and a multimode coupler to achieve pulsed vortex beam output in an all-fiber system. By preparing the metasurface material on the end face of a large-core multimode fiber, a specific refractive index distribution is generated inside the optical fiber, which effectively solves the shortcoming that the contact area of ​​the light beam in the single-mode fiber is too small to generate phase modulation, and the design parameters of the metasurface structure are adjusted to achieve precise control of the pulsed vortex beam. The present invention combines the advantages of metasurfaces and spatiotemporal mode-locking, and provides a new way for high-dimensional optical information encoding and transmission.

[0038] Technicians in the relevant field can clearly understand that, for the convenience and simplicity of description, the specific working process of the space-time mode-locked pulse vortex beam based on the metasurface described above can refer to the corresponding device in the aforementioned embodiment, and will not be repeated here.

[0039] In addition, in the description of the embodiments of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0040] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the 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 limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0041] Finally, it should be noted that the above-described embodiments are only specific implementations of the present invention, which are used to illustrate the technical solutions of the present invention, rather than to limit them. The protection scope of the present invention is not limited thereto. Although the present invention is described in detail with reference to the above-described embodiments, ordinary technicians in the field should understand that any technician familiar with the technical field can still modify the technical solutions recorded in the above-described embodiments within the technical scope disclosed by the present invention, or can easily think of changes, or make equivalent replacements for some of the technical features therein; and these modifications, changes or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A method for generating all-fiber spatiotemporal mode-locked vortex light based on a metasurface, characterized in that: include: A single-mode pump, a multi-mode wavelength division multiplexer, a few-mode gain fiber, a multi-mode isolator, a metasurface saturable absorber, a first multi-mode polarization controller, a multi-mode output coupler, and a second multi-mode polarization controller are sequentially connected through optical fibers; the multi-mode wavelength division multiplexer, the few-mode gain fiber, the multi-mode polarization-independent isolator, the first multi-mode polarization controller, the multi-mode metasurface tilted grating saturable absorber, and the multi-mode output coupler are sequentially connected end to end through a multi-mode optical fiber to form a time-space mode-locked fiber laser; the second multi-mode polarization controller is connected to a laser detection instrument to detect the output laser characteristics.

2. The laser according to claim 1, characterized in that: The few-mode gain fiber is used to generate signal light based on pump light, wherein the few-mode gain fiber can be a few-mode erbium-doped fiber, a few-mode ytterbium-doped fiber, a few-mode thulium-doped fiber, etc.

3. The laser according to claim 1, characterized in that: The metasurface saturable absorber is a metasurface material prepared on the end face of an optical fiber jumper, wherein the metasurface material is a device for generating a pulsed vortex light beam.

4. The laser according to claim 1, characterized in that The output unit includes a multimode fiber coupler and a second polarization controller connected in sequence through a multimode fiber; wherein, The second polarization controller is used for adjusting the output state of the spatiotemporal mode-locked pulse vortex beam.

5. The laser according to claim 3, wherein the metasurface material in the metasurface saturable absorber is gold, silver, etc.; the metasurface structure is nanorods, nanohole rings, nanocubes, tilted gratings, etc.

6. The system according to claim 1, characterized in that The single-mode pump light source is a laser diode or a continuous light laser.

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