Photon lantern for double-ring optical fiber laser and manufacturing method

Abstract

The invention provides a photon lantern for a double-ring optical fiber laser and a manufacturing method, and belongs to the field of optical communication. The photon lantern comprises an optical fiber array, a transition area and a few-mode port which are connected in sequence; the optical fiber array is a part which is formed by placing a preset number of 980nm single-mode optical fibers containing claddings and two 1550nm few-mode optical fibers containing claddings in a quartz capillary tube and carrying out heat insulation tapering to a preset stretching length according to a preset stretching ratio and then keeping the shape unchanged; the transition area is a part with the shape changed after tapering, and the die-less port is a port part with the shape changed after tapering. The photon lantern can realize 980 / 1550nm double-ring type, namely, 980nm wavelength mode selective conversion, 1550nm wavelength mode maintenance and low-loss closed-loop transmission, can be used for constructing an optical fiber double-ring laser cavity, provides an effective device for generating a plurality of 1550nm high-order mode lasers, and has the advantages of wide application range and wide application range. When the laser is added into a double-ring optical fiber laser, direct oscillation and controllable output of a plurality of 1550nm high-order transverse mode lasers can be realized.

Description

Technical Field

[0001] The present invention relates to the field of optical communication, and in particular to a photon lantern for a dual-ring optical fiber laser and a manufacturing method thereof. Background Art

[0002] The generation of high-order transverse mode lasers in optical fibers and related application research are currently cutting-edge topics in the field of optics. In optical fiber communication technology, high-order modes can be used as new degrees of freedom to expand communication channels, break through the upper limit of single-mode transmission capacity, and achieve high-bandwidth, large-capacity information transmission. In terms of optical imaging, light beams in high-order modes can break through the diffraction limit and improve the resolution of microscopic imaging. In addition, high-order mode lasers also show important value in many fields such as optical tweezers, laser micromachining, and high-dimensional quantum entanglement.

[0003] For dual-ring fiber lasers, the generation of high-order transverse mode lasers in optical fibers is currently mainly achieved through mode conversion devices. However, due to the structural and performance constraints of existing optical fiber mode conversion devices, only the first few high-order transverse modes can be generated, and the number of controllable transverse modes is very limited. When using dual-ring lasers, how to simply and efficiently generate multiple high-order transverse mode lasers in optical fibers is a problem that needs to be solved. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides a photon lantern for a dual-ring fiber laser and a manufacturing method thereof.

[0005] The present invention provides a photon lantern for a dual-ring fiber laser, comprising: a fiber array, a transition zone and a few-mode port connected in sequence; the fiber array is a portion of a preset number of 980nm single-mode optical fibers containing claddings and two 1550nm few-mode optical fibers containing claddings placed in a quartz capillary, and the shape remains unchanged after adiabatic tapering to a preset stretched length according to a preset stretching ratio; the transition zone is a portion whose shape changes after tapering, and the few-mode port is a port portion whose shape changes after tapering; wherein the stretching ratio is determined according to the normalized frequency of the few-mode optical fibers so that the few-mode port generates a linearly polarized LP mode, and the preset number corresponds to the number of modes applied to the photon lantern.

[0006] According to a photon lantern for a dual-ring fiber laser provided by the present invention, the preset number includes 3, 6, 10 and 15.

[0007] According to a photon lantern for a dual-ring fiber laser provided by the present invention, the optical fiber arrangement before tapering is as follows: the few-mode optical fibers are symmetrical about the center, the periphery of the overall array of the few-mode optical fibers and the single-mode optical fibers is arranged in a regular polygon, and adjacent optical fibers of the single-mode optical fibers are arranged at equal intervals.

[0008] According to a photon lantern for a dual-ring fiber laser provided by the present invention, the LP modes are LP 01 Mode, LP 11a and LP 11b mode, accordingly, the preset number is 3, and the optical fiber arrangement before tapering is as follows: one single-mode optical fiber is located in the center, the remaining optical fibers are arranged in a regular quadrilateral, two few-mode optical fibers are located on the diagonals of the quadrilateral, and adjacent single-mode optical fibers are arranged at equal intervals.

[0009] According to a photon lantern for a dual-ring fiber laser provided by the present invention, the core and cladding refractive indices of the 980nm single-mode optical fiber are 1.45 and 1.444 respectively, the core and cladding refractive indices of the 1550nm few-mode optical fiber are 1.4669 and 1.444 respectively, and the refractive index of the quartz capillary is 1.438.

[0010] According to a photon lantern for a dual-ring fiber laser provided by the present invention, the core and cladding sizes of the 980nm single-mode optical fiber located in the center are 6μm and 125μm respectively, the core and cladding sizes of the two 980nm single-mode optical fibers located in the ring are 4μm and 125μm respectively, and the core and cladding sizes of the 1550nm few-mode optical fiber are 15μm and 125μm respectively.

[0011] According to a photon lantern for a dual-ring fiber laser provided by the present invention, the inner diameter of the quartz capillary is 400 μm and the outer diameter is 415 μm.

[0012] The present invention also provides a method for manufacturing a photon lantern device for a dual-ring fiber laser, comprising: placing a preset number of 980nm single-mode optical fibers containing claddings and two 1550nm few-mode optical fibers containing claddings in a quartz capillary; adiabatically tapering the quartz capillary with the built-in optical fiber to a preset stretched length according to a preset stretching ratio; wherein the stretching ratio is determined based on the normalized frequency of the few-mode optical fiber so that the few-mode port generates an LP mode, the few-mode port being the port portion whose shape is changed after tapering, and the preset number corresponds to the number of modes applied by the photon lantern.

[0013] According to a method for making a photon lantern for a dual-ring fiber laser provided by the present invention, the optical fiber arrangement before taper is as follows: the few-mode optical fiber is symmetrical about the center, the periphery of the few-mode optical fiber and the single-mode optical fiber overall array is arranged in a regular polygon, and the adjacent optical fibers of the single-mode optical fiber are arranged at equal intervals.

[0014] According to a method for manufacturing a photon lantern for a dual-ring fiber laser provided by the present invention, the LP modes are LP 01 Mode, LP 11a and LP 11bmode, accordingly, the preset number is 3, and the optical fiber arrangement before tapering is as follows: one single-mode optical fiber is located in the center, the remaining optical fibers are arranged in a regular quadrilateral, two few-mode optical fibers are located on the diagonals of the quadrilateral, and adjacent single-mode optical fibers are arranged at equal intervals.

[0015] The present invention also provides a dual-ring fiber laser, comprising: a 980nm laser and a photon lantern of the dual-ring fiber laser described in any one of the above items; the 980nm laser is connected to each 980nm single-mode optical fiber of the photon lantern, and the pump light injected by different 980nm single-mode optical fibers passes through the photon lantern to achieve selective excitation of the fundamental mode to a higher-order linear polarization mode; the two 1550nm few-mode optical fibers of the photon lantern are respectively connected to the few-port ring to form a dual-ring laser cavity, and the dual-ring laser cavity is connected with a few-mode erbium-doped optical fiber as a gain optical fiber to convert the wavelength running in the cavity to 1550nm.

[0016] The photon lantern for a dual-ring fiber laser provided by the present invention and the manufacturing method thereof can realize a 980 / 1550nm dual-ring, i.e., selective conversion of a 980nm wavelength mode, retention of a 1550nm wavelength mode, and low-loss closed-loop transmission. The photon lantern can be used to construct a full multimode (few-mode) fiber dual-ring laser cavity, and provide an effective device for generating multiple 1550nm high-order mode lasers. Adding the photon lantern to a dual-ring fiber laser can realize direct oscillation and controllable output of multiple 1550nm high-order transverse mode lasers. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 It is a schematic diagram of the structure of a photon lantern for a dual-ring fiber laser provided by the present invention;

[0019] Figure 2 It is a schematic cross-sectional view of a few-mode port of a 3+2 photon lantern for a dual-ring fiber laser provided by the present invention;

[0020] Figure 3 It is a schematic diagram of the change of the effective refractive index of the mode corresponding to the wavelength of 980nm provided by the present invention;

[0021] Figure 4 It is a schematic diagram of the simulation results of the mode field evolution corresponding to the new 3+2 photon lantern for 980nm wavelength laser transmission provided by the present invention under different taper ratio conditions;

[0022] Figure 5 It is a schematic diagram of the new 3+2 photon lantern few-mode end face for 1550nm laser transmission provided by the present invention;

[0023] Figure 6 It is a schematic diagram of the change of the effective refractive index of the 1550nm mode provided by the present invention with the taper ratio;

[0024] Figure 7 It is a schematic diagram of the simulation results of the mode field evolution corresponding to the new 3+2 photon lantern of 1550nm laser transmission provided by the present invention under different taper ratio conditions;

[0025] Figure 8 It is a schematic flow chart of a method for making a photon lantern for a dual-ring fiber laser provided by the present invention;

[0026] Fig. 9 It is a schematic diagram of a dual-ring fiber laser provided by the present invention;

[0027] Explanation of the reference numerals: 1, optical fiber array; 2, transition zone; 3, few-mode port; 1-1, 980 nm single-mode optical fiber; 1-2, 1550 nm few-mode optical fiber; 101 (102, 103), 980 nm single-mode optical fiber; 200 (201), 1550 nm few-mode optical fiber. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. 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.

[0029] In order to solve the problem of the small number of laser transverse modes in dual-ring fiber lasers, the present invention proposes a self-matching photon lantern device and a manufacturing method. For 980nm band lasers, it can selectively excite multiple high-order transverse modes and has mode selection characteristics; for 1550nm band lasers, it can enable multiple high-order transverse modes to be transmitted in a closed loop and has a self-cavity characteristic. The above 980 / 1550nm dual-band multiplexing characteristics make the self-matching photon lantern particularly suitable for constructing a full few-mode fiber ring cavity laser, realizing the generation and flexible switching of multiple high-order transverse mode lasers at 1550nm.

[0030] The dual-ring fiber laser based on the new n+2 photon lantern device can generate high-order transverse mode lasers, which have three major performances: 980 / 1550nm dual-band multiplexing, 980nm wavelength mode selection, and 1550nm wavelength few-mode fiber self-cavity. Finally, multiple 1550nm high-order transverse mode lasers can be directly oscillated and controllably output in the full few-mode fiber dual ring cavity. The present invention has significant advantages such as a large number of output transverse mode lasers, high mode conversion efficiency, low transmission loss, and no reliance on wavelength division multiplexing devices.

[0031] Combine the following Figure 1-Figure 9 The present invention describes a photon lantern for a dual-ring fiber laser and a method for making the same. Figure 1 Schematic diagram of the photon lantern structure of the dual-ring fiber laser provided by the present invention, such as Figure 1 As shown, the photon lantern of the dual-ring fiber laser provided by the present invention comprises: a fiber array 1, a transition zone 2 and a few-mode port 3 connected in sequence; the fiber array 1 is a portion of a preset number of 980nm single-mode optical fibers 1-1 containing cladding and two 1550nm few-mode optical fibers 1-2 containing cladding placed in a quartz capillary, and the shape remains unchanged after adiabatic tapering to a preset stretched length according to a preset stretching ratio; the transition zone 2 is a portion whose shape changes after tapering, and the few-mode port 3 is a port portion whose shape changes after tapering; wherein the stretching ratio is determined according to the normalized frequency of the few-mode optical fiber, so that the few-mode port 3 generates a linearly polarized LP mode, and the preset number corresponds to the number of modes applied by the photon lantern.

[0032] Among them, the taper ratio is the ratio of the cross-sectional diameter of the coupling zone after taper to the cross-sectional diameter before taper, and the taper length is the length added after taper. The taper ratio is closely related to the normalized frequency of the few-mode port of the photon lantern, and ultimately determines the mode of the few-mode port. The preset taper ratio and the preset taper length can be obtained through simulation results, such as beam propagation method and finite element analysis, or through experiments.

[0033] The fiber array gradually merges into one during the adiabatic taper process, and the 980nm single-mode fiber core and the 1550nm few-mode fiber core gradually become thinner until they lose their ability to bind light. The original cladding in the fiber array becomes the new fiber core, and the low-refractive-index quartz sleeve outside becomes the new cladding. When the taper is stretched to a certain length according to the preset taper ratio, the taper is stopped, and a new few-mode waveguide is finally formed, namely the few-mode port 3, whose parameters are similar to those of the 1550nm few-mode fiber, supporting mode closed-loop low-loss transmission.

[0034] The photon lantern of the dual-ring fiber laser of the present invention can realize the 980 / 1550nm dual-ring, that is, the selective conversion of the 980nm wavelength mode, the retention of the 1550nm wavelength mode, and low-loss closed-loop transmission. It can be used to construct a full multimode (few-mode) fiber dual-ring laser cavity, and provide an effective device for the generation of multiple 1550nm high-order mode lasers. Adding it to the dual-ring fiber laser can realize the direct oscillation and controllable output of multiple 1550nm high-order transverse mode lasers.

[0035] In one embodiment, the preset number n of 980 nm single mode optical fibers includes 3, 6, 10, and 15.

[0036] In one embodiment, the optical fiber arrangement before tapering is as follows: the few-mode optical fibers are symmetrical about the center, the periphery of the overall array of the few-mode optical fibers and the single-mode optical fibers is arranged in a regular polygon, and adjacent optical fibers of the single-mode optical fibers are arranged at equal intervals.

[0037] Taking into account that the structure of the high-order transverse mode is a symmetrical structure, when arranging the embodiment of the present invention, the outer periphery of the optical fiber array is equally spaced, and the structure is a regular polygon, so that the effect of generating high-order modes is better, and when arranging, the few-mode optical fiber is arranged in a centrally symmetrical manner. When the above conditions are met, the adjacent single-mode optical fibers are arranged at equal intervals, thereby improving the coupling efficiency of the few-mode optical fiber.

[0038] In one embodiment, the LP modes are LP 01 Mode, LP 11a and LP 11b mode, accordingly, the preset number is 3, and the optical fiber arrangement before tapering is as follows: one single-mode optical fiber is located in the center, the remaining optical fibers are arranged in a regular quadrilateral, two few-mode optical fibers are located on the diagonals of the quadrilateral, and adjacent single-mode optical fibers are arranged at equal intervals.

[0039] Take the new 3+2 photon lantern as an example. The schematic diagram of the new 3+2 photon lantern is as follows: Figure 1 The few-mode port can selectively excite the three linear polarization modes of LP01, LP11a and LP11b. The number of single-mode fibers in the corresponding 980nm single-mode fiber cluster is 3. The three 980nm single-mode fibers correspond to Figure 1 100, 101 and 102 in the figure. Correspondingly, the 1550nm few-mode optical fiber can use three-mode optical fiber corresponding to 200 and 201 in the figure.

[0040] According to the relationship between the geometric arrangement of optical fibers in photon lanterns and the effect on mode conversion, for photon lanterns that support the propagation and conversion of LPmn modes (m is the radial order of the mode field, n is the angular order of the mode field), the optical fiber array should be arranged in the form of m concentric circles. The number of optical fibers on each ring should be N = 2nmax +1, thereby achieving selective excitation of the modes in the photon lantern. When the modes supported by the photon lantern are LP01, LP11a and LP11b, m = 1, n max =1, N=3, three 980nm single-mode optical fibers should be distributed on a ring.

[0041] In the embodiment of the present invention, in order to combine the mode field evolution of the few-mode fiber, and considering that the three-mode fiber used to transmit the 1550nm laser is also a part of the new 3+2 photon lantern, but it does not inject the 980nm light beam itself, the five optical fibers can be arranged in the manner of the above embodiment, that is, in the embodiment of the present invention, a single-mode fiber is located in the center, and the remaining optical fibers form a regular quadrilateral. Naturally, since the few-mode fiber is symmetrical about the center, the few-mode fiber is located on the diagonal of the regular quadrilateral, and the two outer single-mode fibers are naturally located on the other diagonal, while ensuring that the adjacent single-mode fibers are equally spaced to support the functional requirements of the new 3+2 photon lantern for 980 / 1550nm dual-band mode multiplexing.

[0042] In one embodiment, the core and cladding refractive indices of the 980nm single-mode optical fiber are 1.45 and 1.444, respectively, and the core and cladding refractive indices of the 1550nm few-mode optical fiber are 1.4669 and 1.444, respectively.

[0043] In one embodiment, the core and cladding sizes of the 980nm single-mode optical fiber located in the center are 6μm and 125μm respectively, the core and cladding sizes of the two 980nm single-mode optical fibers located in the ring are 4μm and 125μm respectively, and the core and cladding sizes of the 1550nm few-mode optical fiber are 15μm and 125μm respectively.

[0044] In one embodiment, the refractive index of the quartz capillary is 1.438, the inner diameter of the quartz capillary is 400 μm, and the outer diameter is 415 μm.

[0045] Furthermore, the present invention designs the core and cladding refractive indices of the three 980nm single-mode optical fibers in the novel 3+2 photon lantern to be 1.45 and 1.444, respectively, and the core and cladding sizes of the two 980nm single-mode optical fibers are designed to be 4μm and 125μm, respectively, which can better selectively excite LP 11a and LP 11b mode, another 980nm single-mode fiber core and cladding size are designed to be 6μm and 125μm, and the LP 01 The core and cladding refractive indices of the 1550nm three-mode optical fiber are designed to be 1.4669 and 1.444, respectively, and the core and refractive index sizes are designed to be 15μm and 125μm, respectively.

[0046] It should be noted that the above-mentioned optical fiber and cladding dimensions are not conventional choices in the art, but are dimension parameters with better coupling effects set to better match the arrangement of the three single-mode optical fibers and the two few-mode optical fibers in the above-mentioned embodiment.

[0047] When the claddings of the above five optical fibers are all 125 μm, the inner diameter of the outermost low-refractive-index quartz capillary is about 400 μm, the outer diameter thereof is designed to be 415 μm, and the refractive index is designed to be 1.438.

[0048] In one embodiment, the stretching ratio is 0.1.

[0049] According to the above parameters, the new 3+2 photon lantern is simulated and set to simulate the light field evolution process of the 980nm light wave inside the new 3+2 photon lantern. Figure 2 Schematic diagram of the cross section of the few-mode port of the 3+2 photon lantern for the dual-ring fiber laser provided by the present invention, wherein the highlighted parts are the cores of the 980nm single-mode optical fibers 100, 101 and 102, and the core sizes of 100 and 101 are the same (4μm), corresponding to the excitation LP 11a With LP 11b mode, the core of 102 (6μm) corresponds to the excitation LP 01 model. Figure 3 When the taper ratio reaches 0.1, the fundamental mode in the original 100, 101 and 102 single-mode fibers excites the corresponding LP at the minority-mode port. 01 LP 11a With LP 11b mode to achieve selective excitation of the 980nm band mode. Figure 4 The simulation results of mode field evolution of the new 3+2 photon lantern for 980nm laser transmission under different taper ratios.

[0050] According to the above parameters, the new 3+2 photon lantern is simulated and set up to simulate the light field evolution process of the 1550nm light wave inside the new 3+2 photon lantern. Figure 5 This is a schematic diagram of the cross-section of the few-mode end of the new 3+2 photon lantern. The highlighted part is the 1550nm few-mode fiber core after tapering. Figure 6 The effective refractive index of the 1550nm mode changes with the taper ratio. When the taper ratio reaches 0.1, the 1550nm three-mode fiber can stably transmit LP 01 and LP 11 mode. As the taper ratio decreases, LP 11 The mode first leaks into the cladding. When the taper ratio is lower than 0.05, the core can no longer guide the mode transmission, and the cladding of the fiber array becomes the new "core" and guides the mode to transmit stably. Figure 7 When the taper ratio reaches 0.05, the LP injected into the original 1550nm three-mode fiber01 LP 11a With LP 11b mode, which can be matched with the initial mode field at the few-mode port, that is, the 1550nm mode can maintain its mode morphology through the new 3+2 photon lantern, and low-loss closed-loop transmission can be achieved when connected to the few-mode optical fiber.

[0051] The new 3+2 photon lantern can solve the incompatibility problem between single mode and few mode when conventional photon lanterns are used to build fiber lasers. The few-mode fiber added to the fiber array can match the few-mode port formed by the taper to achieve dual closed-loop transmission of the 1550nm mode. In addition, the new 3+2 photon lantern has the characteristics of 980 / 1550nm dual-band mode multiplexing, and can be used to build fiber lasers to get rid of the dependence on wavelength division multiplexing devices. The new 3+2 photon lantern is used to build a full few-mode fiber dual ring cavity laser to generate high-order mode lasers in the 1550nm band.

[0052] The novel n+2 photon lantern of the present invention can realize the 980 / 1550nm dual-band mode multiplexing characteristics, making it suitable for constructing fiber lasers and getting rid of the dependence on wavelength division multiplexers. In addition, in the novel n+2 photon lantern, the matching characteristics of the input 1550nm few-mode fiber and the output (multimode) few-mode port can be used to construct a full few-mode fiber dual-ring laser cavity, realizing the direct oscillation and output of multiple high-order mode lasers in the full few-mode fiber dual-ring laser cavity, and one device can realize the generation of high-order mode outputs of two wavelengths. The high-order transverse mode generation method based on the dual-ring fiber laser of the present invention has strong practicality, low manufacturing cost, simple use process, and mode conversion efficiency is much higher than other fiber laser systems, and the novel n+2 photon lantern can realize low-loss insertion in the laser system, which is suitable for large-scale promotion and use and generates certain economic value.

[0053] By adding two few-mode fibers to the fiber array of the photon lantern, a new n+2 photon lantern was constructed, which can serve the generation of multiple high-order transverse modes of 1550nm. The new n+2 photon lantern can realize 980 / 1550nm dual-band mode multiplexing, and the 980nm pump light input through different single-mode fibers can be selectively converted into the corresponding high-order transverse modes, and the self-cavity characteristics of the few-mode fiber can enable the 1550nm high-order transverse mode to be transmitted in a low-loss closed loop.

[0054] The research on the new n+2 photon lantern in this invention enriches the types and functions of photon lanterns. With the further deepening of the research on photon lantern devices and the continuous improvement of processing and manufacturing methods, the new n+2 photon lantern can serve the generation of 1550nm high-order transverse mode lasers and achieve the output of dozens or even hundreds of transverse modes.

[0055] By precisely controlling the parameters and arrangement of the fiber array and the taper ratio of the new n+2 photon lantern, efficient conversion of the 980 / 1550nm dual-band modes in the transition zone is achieved. The few-mode fiber port formed by the few-mode fiber and the taper can perform low-loss closed-loop transmission of multiple high-order transverse modes.

[0056] Using the new n+2 photon lantern to build a full few-mode fiber dual ring cavity laser to generate 1550nm corresponding high-order transverse mode laser can effectively simplify the laser structure and reduce the dependence on other few-mode fiber devices. More importantly, the new n+2 photon lantern studied in this project has strong scalability and can be used to achieve the generation and conversion of multiple high-order modes, laying a key technical foundation for the efficient generation and flexible control of high-order transverse mode lasers.

[0057] The following is a description of the method for manufacturing a photon lantern for a dual-ring fiber laser provided by the present invention. The method for manufacturing a photon lantern for a dual-ring fiber laser described below and the photon lantern for a dual-ring fiber laser described above can be referenced to each other.

[0058] Figure 8 Schematic diagram of the process of manufacturing a photon lantern for a dual-ring fiber laser provided by the present invention, such as Figure 8 As shown, the present invention provides a method for manufacturing a photon lantern for a dual-ring fiber laser, comprising:

[0059] 801. Place a preset number of 980 nm single-mode optical fibers containing cladding and two 1550 nm few-mode optical fibers containing cladding in a quartz capillary;

[0060] 802. Adiabatically tapering the quartz capillary tube with the built-in optical fiber to a preset stretching length according to a preset stretching ratio;

[0061] Among them, the stretching ratio is determined according to the normalized frequency of the few-mode optical fiber so that the few-mode port generates an LP mode, and the few-mode port is the port part whose shape is changed after tapering, and the preset number corresponds to the number of modes applied by the photon lantern.

[0062] In one embodiment, the optical fiber arrangement before tapering is as follows: the few-mode optical fibers are symmetrical about the center, the periphery of the overall array of the few-mode optical fibers and the single-mode optical fibers is arranged in a regular polygon, and adjacent optical fibers of the single-mode optical fibers are arranged at equal intervals.

[0063] In one embodiment, the LP modes are LP 01 Mode, LP 11a and LP 11bmode, accordingly, the preset number is 3, and the optical fiber arrangement before tapering is as follows: one single-mode optical fiber is located in the center, the remaining optical fibers are arranged in a regular quadrilateral, two few-mode optical fibers are located on the diagonals of the quadrilateral, and adjacent single-mode optical fibers are arranged at equal intervals.

[0064] The method embodiments provided in the embodiments of the present invention are for realizing the above-mentioned device embodiments. For specific processes and detailed contents, please refer to the above-mentioned device embodiments, which will not be described in detail here.

[0065] The photon lantern manufacturing method for a dual-ring fiber laser provided in the embodiment of the present invention has the same implementation principle and technical effects as those of the aforementioned photon lantern embodiment for a dual-ring fiber laser. For the sake of brief description, for matters not mentioned in the embodiment of the photon lantern manufacturing method for a dual-ring fiber laser, reference may be made to the corresponding contents in the aforementioned photon lantern embodiment for a dual-ring fiber laser.

[0066] Fig. 9 Schematic diagram of the structure of the dual-ring fiber laser provided by the present invention, such as Fig. 9 As shown, the dual-ring fiber laser includes: a 980nm laser and a photon lantern of the dual-ring fiber laser described in any of the above embodiments; the 980nm laser is connected to each 980nm single-mode optical fiber of the photon lantern, and the pump light injected by different 980nm single-mode optical fibers passes through the photon lantern to achieve selective excitation of the fundamental mode to a higher-order linear polarization mode; the two 1550nm few-mode optical fibers of the photon lantern are respectively connected to the few-port ring to form a dual-ring laser cavity, and the dual-ring laser cavity is connected with a few-mode erbium-doped optical fiber as a gain optical fiber to convert the wavelength running in the cavity to 1550nm.

[0067] like Fig. 9 As shown. The 980nm single-mode fiber bundle of the new 3+2 photon lantern is connected to the 980nm laser through an optical switch. The pump light injected by different 980nm single-mode fibers passes through the new photon lantern to achieve selective excitation of the fundamental mode to the higher-order linear polarization mode. The 1550nm three-mode fiber of the new photon lantern is connected to the few-mode port through a beam splitter to form a dual-ring laser cavity. The few-mode erbium-doped fiber is introduced into the ring cavity as a gain fiber to convert the wavelength running in the cavity to 1550nm, and the 1550nm high-order transverse mode can oscillate in the dual-ring cavity. In addition, an isolator is introduced into the system to ensure unidirectional transmission of light; a polarization controller is introduced to adjust the polarization state of the mode field and generate a vector beam. A spectrum analyzer is used to measure the wavelength and spectral characteristics of the output laser, and a 1550nm CCD is used to observe the light field distribution of the output laser.

[0068] The device embodiments described above are merely illustrative, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Ordinary technicians in this field can understand and implement it without paying creative labor.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A photon lantern for a dual-ring fiber laser, characterized in that: include: The fiber array, transition zone, and few-mode port are connected in sequence; The optical fiber array is a portion in which a preset number of 980nm single-mode optical fibers with cladding and two 1550nm few-mode optical fibers with cladding are placed in a quartz capillary and adiabatically tapered to a preset stretching length according to a preset stretching ratio, and the shape remains unchanged; The transition zone is a portion whose shape is changed after taper, and the few-mode port is a port portion whose shape is changed after taper; The stretching ratio is determined according to the normalized frequency of the few-mode optical fiber so that the few-mode port generates a linearly polarized LP mode, and the preset number corresponds to the number of modes applied by the photon lantern.

2. The photon lantern for a dual-ring fiber laser according to claim 1, characterized in that: The preset numbers include 3, 6, 10 and 15.

3. The photon lantern for a dual-ring fiber laser according to claim 1, characterized in that: The optical fiber arrangement before taper is as follows: the few-mode optical fibers are symmetrical about the center, the periphery of the few-mode optical fibers and the single-mode optical fibers are arranged in a regular polygon, and adjacent single-mode optical fibers are arranged at equal intervals.

4. The photon lantern for a dual-ring fiber laser according to claim 1 or 3, characterized in that: The LP modes are LP 01 Mode, LP 11a and LP 11b mode, accordingly, the preset number is 3, and the optical fiber arrangement before taper is: One single-mode optical fiber is located in the center, and the other optical fibers are arranged in a regular quadrilateral. Two few-mode optical fibers are located on the diagonals of the quadrilateral, and adjacent single-mode optical fibers are arranged at equal intervals.

5. The photon lantern for a dual-ring fiber laser according to claim 4, characterized in that: The core and cladding refractive indices of the 980nm single-mode optical fiber are 1.45 and 1.444 respectively, and the core and cladding refractive indices of the 1550nm few-mode optical fiber are 1.4669 and 1.444 respectively.

6. The photon lantern for a dual-ring fiber laser according to claim 4, characterized in that: The core and cladding sizes of the 980nm single-mode fiber located in the center are 6μm and 125μm respectively, the core and cladding sizes of the two 980nm single-mode fibers located in the ring are 4μm and 125μm respectively, and the core and cladding sizes of the 1550nm few-mode fiber are 15μm and 125μm respectively.

7. The photon lantern for a dual-ring fiber laser according to claim 4, characterized in that: The refractive index of the quartz capillary is 1.438, the inner diameter of the quartz capillary is 400 μm, and the outer diameter is 415 μm.

8. A method for making a photon lantern for a dual-ring fiber laser, characterized in that: include: A preset number of 980 nm single-mode optical fibers containing cladding and two 1550 nm few-mode optical fibers containing cladding are placed in a quartz capillary; Adiabatically taper the quartz capillary tube with the built-in optical fiber to a preset stretching length according to a preset stretching ratio; Among them, the stretching ratio is determined according to the normalized frequency of the few-mode optical fiber so that the few-mode port generates an LP mode, and the few-mode port is the port part whose shape is changed after tapering, and the preset number corresponds to the number of modes applied by the photon lantern.

9. The method for making a photon lantern for a dual-ring fiber laser according to claim 8, characterized in that: The optical fiber arrangement before taper is as follows: the few-mode optical fibers are symmetrical about the center, the periphery of the few-mode optical fibers and the single-mode optical fibers are arranged in a regular polygon, and adjacent single-mode optical fibers are arranged at equal intervals.

10. A dual-ring fiber laser, characterized in that: include: A 980nm laser and a photon lantern of a dual-ring fiber laser as claimed in any one of claims 1 to 7; The 980nm laser is connected to each 980nm single-mode optical fiber of the photon lantern, and the pump light injected from different 980nm single-mode optical fibers passes through the photon lantern to achieve selective excitation of the fundamental mode to a higher-order linear polarization mode; The two 1550nm few-mode optical fibers of the photon lantern are respectively connected to the few-port rings to form a double-ring laser cavity. The double-ring laser cavity is connected with a few-mode erbium-doped optical fiber as a gain optical fiber to convert the wavelength running in the cavity to 1550nm.

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