CN116594101A - Axial absorption gradual change optical fiber and preparation method thereof - Google Patents

Axial absorption gradual change optical fiber and preparation method thereof Download PDF

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CN116594101A
CN116594101A CN202310861758.3A CN202310861758A CN116594101A CN 116594101 A CN116594101 A CN 116594101A CN 202310861758 A CN202310861758 A CN 202310861758A CN 116594101 A CN116594101 A CN 116594101A
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optical fiber
layer
cladding
axial
fiber
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CN116594101B (en
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林贤峰
张安军
王一礴
吴怀
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Wuhan Changjin Photonics Technology Co ltd
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Wuhan Changjin Photonics Technology Co ltd
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    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/02Optical fibres with cladding with or without a coating
    • G02B6/028Optical fibres with cladding with or without a coating with core or cladding having graded refractive index
    • CCHEMISTRY; METALLURGY
    • C03GLASS; MINERAL OR SLAG WOOL
    • C03BMANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B37/00Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
    • C03B37/01Manufacture of glass fibres or filaments
    • C03B37/012Manufacture of preforms for drawing fibres or filaments
    • C03B37/01205Manufacture of preforms for drawing fibres or filaments starting from tubes, rods, fibres or filaments
    • C03B37/01211Manufacture of preforms for drawing fibres or filaments starting from tubes, rods, fibres or filaments by inserting one or more rods or tubes into a tube
    • CCHEMISTRY; METALLURGY
    • C03GLASS; MINERAL OR SLAG WOOL
    • C03BMANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B37/00Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
    • C03B37/01Manufacture of glass fibres or filaments
    • C03B37/02Manufacture of glass fibres or filaments by drawing or extruding, e.g. direct drawing of molten glass from nozzles; Cooling fins therefor
    • C03B37/025Manufacture of glass fibres or filaments by drawing or extruding, e.g. direct drawing of molten glass from nozzles; Cooling fins therefor from reheated softened tubes, rods, fibres or filaments, e.g. drawing fibres from preforms
    • C03B37/027Fibres composed of different sorts of glass, e.g. glass optical fibres
    • C03B37/02745Fibres having rotational spin around the central longitudinal axis, e.g. alternating +/- spin to reduce polarisation mode dispersion
    • CCHEMISTRY; METALLURGY
    • C03GLASS; MINERAL OR SLAG WOOL
    • C03BMANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B37/00Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
    • C03B37/01Manufacture of glass fibres or filaments
    • C03B37/02Manufacture of glass fibres or filaments by drawing or extruding, e.g. direct drawing of molten glass from nozzles; Cooling fins therefor
    • C03B37/025Manufacture of glass fibres or filaments by drawing or extruding, e.g. direct drawing of molten glass from nozzles; Cooling fins therefor from reheated softened tubes, rods, fibres or filaments, e.g. drawing fibres from preforms
    • C03B37/027Fibres composed of different sorts of glass, e.g. glass optical fibres
    • C03B37/02763Fibres having axial variations, e.g. axially varying diameter, material or optical properties
    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/02Optical fibres with cladding with or without a coating
    • G02B6/036Optical fibres with cladding with or without a coating core or cladding comprising multiple layers
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01SDEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/06Construction or shape of active medium
    • H01S3/063Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
    • H01S3/067Fibre lasers
    • H01S3/06708Constructional details of the fibre, e.g. compositions, cross-section, shape or tapering
    • H01S3/06716Fibre compositions or doping with active elements
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02PCLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P40/00Technologies relating to the processing of minerals
    • Y02P40/50Glass production, e.g. reusing waste heat during processing or shaping
    • Y02P40/57Improving the yield, e-g- reduction of reject rates

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  • Chemical & Material Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Optics & Photonics (AREA)
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  • Geochemistry & Mineralogy (AREA)
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  • Organic Chemistry (AREA)
  • Electromagnetism (AREA)
  • General Physics & Mathematics (AREA)
  • Plasma & Fusion (AREA)
  • Dispersion Chemistry (AREA)
  • Lasers (AREA)

Abstract

The application provides an axial absorption gradient optical fiber and a preparation method thereof, wherein the axial absorption gradient optical fiber comprises a fiber core layer, an inner cladding layer and a coating layer which are sequentially arranged from inside to outside along the radial direction, at least one cladding layer unit is embedded in the inner cladding layer, the cladding layer unit and the fiber core layer are spirally wound, the screw pitch is in a gradient trend along the axial direction, the refractive index of the fiber core layer is larger than that of the inner cladding layer, the refractive index of the inner cladding layer is larger than that of the cladding layer unit, and the refractive index of the cladding layer unit is larger than that of the coating layer; the axial absorption gradient optical fiber provided by the application not only effectively solves the defect that spiral light and a fiber core layer in the axial absorption gradient optical fiber are difficult to meet, but also improves the pump absorption coefficient of the axial absorption gradient optical fiber and further improves the problem of uneven heat distribution of the axial absorption gradient optical fiber in the axial direction; meanwhile, the preparation method is simple, the adjustment and control of the absorption coefficient of the pump in the preparation process can be realized through automatic equipment, and the stability is good.

Description

Axial absorption gradual change optical fiber and preparation method thereof
Technical Field
The application relates to the field of gain optical fibers, in particular to an axial absorption gradient optical fiber and a preparation method thereof.
Background
The fiber laser and the amplifier have the characteristics of high conversion efficiency, small volume, good beam quality, convenient thermal management, high stability and the like, and are widely applied and rapidly developed in the fields of industry, military, medical treatment, scientific research and the like in recent years. The gain medium of the fiber laser is mainly a gain fiber, the gain fiber absorbs the cladding pumping light and converts the cladding pumping light into signal laser, in order to ensure that the injected pumping light is fully absorbed by the gain fiber, a gain fiber with a certain length is usually selected according to the pumping absorption coefficient of the gain fiber, and the pumping absorption, the core numerical aperture and the like of the gain fiber with a certain length are uniform along the axial direction of the fiber at present.
In the fiber laser, whether forward pumping, backward pumping or bidirectional pumping is adopted, it is difficult to keep the inversion degree of the particle number in the gain fiber with uniform axial absorption consistent; the gain fiber near the pumping end has high pumping degree, high particle number inversion degree, low pumping degree of the gain fiber far from the pumping end and low corresponding particle number inversion degree, so that the particle number inversion degree along the axial direction of the gain fiber is necessarily different, and uneven heat distribution of the gain fiber along the axial direction is caused. The phenomenon of uneven heat distribution of the gain fiber in the axial direction can cause the generation of a thermally induced refractive index grating and the phenomenon of unstable triggering mode; meanwhile, the performance of the laser is reduced due to light heat concentration, and the burning of the gain fiber in the laser is caused when the performance is serious, so that the further improvement of the output power of the high-power fiber laser is limited.
Therefore, there is a need for an axial absorption graded optical fiber and a method for preparing the same to solve the above technical problems.
Disclosure of Invention
The application aims to provide an axial absorption gradient optical fiber and a preparation method thereof, which are used for solving the technical problem of uneven heat distribution of the axial absorption gradient optical fiber in the prior art.
In order to solve the technical problems, the application provides an axial absorption gradient optical fiber, which comprises a fiber core layer, an inner cladding layer and a coating layer which are sequentially arranged from inside to outside along the radial direction, wherein at least one cladding layer unit is embedded in the inner cladding layer, the cladding layer unit and the fiber core layer are spirally wound, and the screw pitch is in a gradient trend along the axial direction;
the refractive index of the fiber core layer is larger than that of the inner cladding layer, the refractive index of the inner cladding layer is larger than that of the cladding layer unit, and the refractive index of the cladding layer unit is larger than that of the coating layer.
In the axial absorption gradient optical fiber provided by the embodiment of the application, the axial absorption gradient optical fiber only comprises the first pumping end, and the pitch corresponding to the repeated torsion period of the cladding unit is gradually reduced along the direction away from the first pumping end.
In the axial absorption gradient optical fiber provided by the embodiment of the application, the axial absorption gradient optical fiber comprises a second pumping end and a third pumping end, and the pitch corresponding to the repeated torsion period of the cladding unit is gradually reduced and then gradually increased along the direction away from the second pumping end or the third pumping end.
In the axial absorption graded optical fiber provided by the embodiment of the application, the repeated torsion period range of the cladding unit is 0.01 m-1 m.
In the axial absorption gradient optical fiber provided by the embodiment of the application, the axial absorption gradient optical fiber comprises two cladding units, and the two cladding units are symmetrically arranged relative to the fiber core layer.
In the axial absorption gradient optical fiber provided by the embodiment of the application, the distance between the two cladding units and the fiber core layer is in a gradient trend along the axial direction.
In the axial absorption graded optical fiber provided by the embodiment of the application, the fiber core layer comprises a matrix layer and a complete packageRare earth oxide layer wrapping matrix layer made of SiO 2 The material of the rare earth oxide layer comprises Yb 2 O 3 、Er 2 O 3 Tm of 2 O 3 At least one of (a) and (b); the material of the inner cladding is SiO 2 The method comprises the steps of carrying out a first treatment on the surface of the The cladding unit is made of SiO doped with fluorine or boron 2
Correspondingly, the application also provides a preparation method of the axial absorption graded optical fiber, which comprises the following steps:
s10, etching the inner wall of a base pipe, and forming a loose layer on the inner wall of the base pipe;
s20, taking down the base tube, soaking the base tube in a rare earth ion solution, and sequentially carrying out oxidation and vitrification treatment on the loose layer soaked by the rare earth ion solution to form a fiber core layer doped with rare earth ions;
s30, fusing and shrinking the base tube in a first temperature range to form an optical fiber preform;
s40, performing quartz tube sleeving on the optical fiber preform rod according to a fixed core-to-cladding ratio after testing to form a sleeve rod;
s50, vertically drilling holes in the inner cladding region in the sleeve rod along the axial direction, and polishing the inner wall of the holes to form first through holes;
s60, filling low-refractive-index materials into the first via holes, and respectively carrying out wire drawing, rotation and coating treatment on the sleeve rods filled with the low-refractive-index materials to form the axial absorption graded optical fiber.
In the method for preparing an axial absorption graded optical fiber provided by the embodiment of the present application, step S60 specifically includes:
s601, placing the sleeve rod in a wire drawing tower, and clamping the sleeve rod by using a chuck;
s602, melting and filament forming the sleeve rod in a second temperature range, and coating the sleeve rod, and simultaneously rotating the chuck to form the axial absorption gradient optical fiber.
In the preparation method of the axial absorption gradient optical fiber provided by the embodiment of the application, the drawing speed range of melting and filament forming the sleeve rod is 1-20 m/min, and the rotating speed range of the chuck is 100-1000 r/min.
The beneficial effects of the application are as follows: compared with the prior art, the application provides an axial absorption graded optical fiber and a preparation method thereof, wherein the axial absorption graded optical fiber comprises a fiber core layer, an inner cladding layer and a coating layer which are sequentially arranged from inside to outside along the radial direction, at least one cladding layer unit is embedded in the inner cladding layer, the cladding layer unit and the fiber core layer are spirally wound and the screw pitch is in a graded trend along the axial direction, wherein the refractive index of the fiber core layer is larger than that of the inner cladding layer, the refractive index of the inner cladding layer is larger than that of the cladding layer unit, and the refractive index of the cladding layer unit is larger than that of the coating layer; according to the axial absorption graded optical fiber provided by the application, at least one cladding unit with a lower refractive index is embedded in the inner cladding, the cladding unit and the fiber core layer are spirally wound and the screw pitch is in a graded trend along the axial direction, so that the defect that spiral light and the fiber core layer are difficult to meet in the axial absorption graded optical fiber is effectively solved, meanwhile, the effective reflection area of pump light in the inner cladding is reduced, the reflection path of the pump light is shortened, the reflection frequency of the inner cladding is improved, the pump absorption coefficient of the axial absorption graded optical fiber is improved, and the problem of uneven heat distribution of the axial absorption graded optical fiber in the axial direction is further improved; meanwhile, the preparation method is simple, the adjustment and control of the absorption coefficient of the pump in the preparation process can be realized through automatic equipment, and the stability is good.
Drawings
FIG. 1 is a schematic end view of an axial absorption graded optical fiber according to embodiment 1 of the present application;
FIG. 2 is a schematic view of a longitudinal structure of an axial absorption graded optical fiber according to embodiment 1 of the present application;
FIG. 3 is a schematic view of another longitudinal structure of an axial absorption graded optical fiber according to embodiment 1 of the present application;
FIG. 4 is a schematic view of a borehole of a casing rod according to embodiment 1 of the present application;
FIG. 5 is a schematic end view of an axial absorption graded optical fiber according to embodiment 2 of the present application;
FIG. 6 is a schematic view of a casing rod borehole in accordance with example 2 of the present application;
FIG. 7 is a schematic view showing the longitudinal structure of an axial absorption gradient optical fiber in embodiment 2 of the present application;
FIG. 8 is a schematic end view of two ends of axial absorption gradient optical fiber in embodiment 3 of the present application;
FIG. 9 is a schematic view of a casing rod borehole in accordance with example 3 of the present application;
fig. 10 is a schematic view showing the longitudinal structure of an axial absorption gradient optical fiber in embodiment 3 of the present application.
Detailed Description
The technical solutions of the embodiments of the present application will be clearly and completely described below in conjunction with the embodiments of the present application, and it is apparent that the described embodiments are only some embodiments of the present application, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present application without making any inventive effort, are intended to fall within the scope of the present application.
Referring to fig. 1 to 10, the present application firstly provides an axial absorption gradient optical fiber 100, wherein the axial absorption gradient optical fiber 100 includes a core layer 10, an inner cladding layer 20 and a coating layer 30 sequentially arranged from inside to outside along a radial direction, at least one cladding layer unit 40 is embedded in the inner cladding layer 20, the cladding layer unit 40 and the core layer 10 are spirally wound, and a pitch is gradually changed along the axial direction;
wherein, the refractive index of the fiber core layer 10 is larger than the refractive index of the inner cladding layer 20, the refractive index of the inner cladding layer 20 is larger than the refractive index of the cladding unit 40, and the refractive index of the cladding unit 40 is larger than the refractive index of the coating layer 30.
According to the axial absorption gradient optical fiber 100 provided by the application, at least one cladding unit 40 with a lower refractive index is embedded in the inner cladding 20, the cladding unit 40 and the fiber core layer 10 are spirally wound and the screw pitch is in a gradient trend along the axial direction, so that the defect that spiral rotation in the axial absorption gradient optical fiber 100 is difficult to be intersected with the fiber core layer 10 is effectively overcome, meanwhile, the effective reflection area of pump light in the inner cladding 20 is reduced, the reflection path of the pump light is shortened, and the reflection frequency of the inner cladding 20 is improved, so that the pump absorption coefficient of the axial absorption gradient optical fiber 100 is improved, and the problem of uneven heat distribution of the axial absorption gradient optical fiber 100 in the axial direction is further improved; meanwhile, the preparation method is simple, the adjustment and control of the absorption coefficient of the pump in the preparation process can be realized through automatic equipment, and the stability is good.
In the embodiment of the present application, the core layer 10 includes a matrix layer and a rare earth oxide layer completely surrounding the matrix layer, and the matrix layer is made of SiO 2 The material of the rare earth oxide layer comprises Yb 2 O 3 、Er 2 O 3 Tm of 2 O 3 At least one of (a) and (b); wherein the core layer 10 achieves absorption of the pump light and converts it into laser light.
Specifically, the refractive index of the core layer 10 is n1, and the gradual change of the pump absorption of the gain fiber along the axial direction can be realized by controlling the gradual change of the doping concentration of the rare earth oxide in the core layer 10 along the axial direction of the fiber.
In the embodiment of the present application, the inner cladding 20 is composed of a matrix SiO 2 The coating layer 30 is composed of acrylic resin; the inner cladding 20 is mainly used for the transmission of pump light; wherein the refractive index of the inner cladding 20 is n3, the refractive index of the coating layer 30 is n4, n3> n4, and the optical waveguide structure formed by the refractive index difference between the optical waveguide structure and the coating layer 30 can realize the transmission of the pump light in the inner cladding 20, and the numerical aperture NA= (n 3) of the inner cladding 20 2 -n4 2 ) 1/2
In the embodiment of the present application, at least one cladding unit 40 is embedded in the inner cladding 20, the cladding unit 40 and the core layer 10 are spirally wound, and the pitch is gradually changed along the axial direction; the gradual change of the pump absorption of the gain fiber along the axial direction can be realized by controlling the gradual change of the pitch of the cladding unit 40 along the axial direction of the fiber, so that the problem of uneven heat distribution of the gradual change of the axial absorption of the fiber 100 along the axial direction can be improved.
Specifically, the core layer 10, the circular inner cladding 20 and the coating layer 30 are axially fixed, while the cladding unit 40 with a lower refractive index is spirally wound around the core layer 10 with the axial center line of the core layer 10 as the axis, and the pitch is axially gradually changed; the distribution of the positions of the lower refractive index cladding elements 40 within the inner cladding 20 is arbitrary.
Further, the refractive index n1 of the core layer 10 > the refractive index n3 of the inner cladding layer 20 > the refractive index n2 of the cladding unit 40 > the refractive index n4 of the coating layer 30; wherein, since the inner cladding 20 is embedded with at least one cladding unit 40 with lower refractive index, not only the defect that the spiral light and the fiber core are difficult to be intersected in the round optical fiber is effectively solved, but also the effective reflection area of the pump light in the inner cladding 20 is reduced, the reflection path of the pump light is shortened, the reflection frequency of the inner cladding 20 is improved, and the pump absorption coefficient of the optical fiber is improved.
According to some embodiments of the present application, the diameters of the core layer 10, inner cladding layer 20, and coating layer 30 are the outermost widths of the layers in radial cross section, which is a common metering means in the art, i.e., the diameter of the inner cladding layer 20 is the diameter of the core layer 10, for example.
In the embodiment of the present application, the cladding unit 40 has a circular structure embedded in the inner cladding 20, the diameter of the cladding unit 40 is larger than the diameter of the core 10, and the diameter of the cladding unit 40 is smaller than the diameter of the inner cladding 20.
Specifically, the repeated twisting period of the cladding unit 40 ranges from 0.01m to 1m, and the material of the cladding unit 40 is fluorine-doped or boron-doped SiO 2
Correspondingly, the embodiment of the application also provides a preparation method of the axial absorption gradient optical fiber 100, and the preparation method of the axial absorption gradient optical fiber 100 comprises the following steps:
s10, etching the inner wall of a base pipe, and forming a loose layer on the inner wall of the base pipe.
Specifically, S10 further includes:
etching the inner wall of the high-purity quartz tube by taking the high-purity quartz tube as a substrate tube; a porous layer is then deposited on the inner wall of the substrate tube.
And S20, taking down the base pipe, soaking the base pipe in a rare earth ion solution, and sequentially carrying out oxidation and vitrification treatment on the loose layer soaked by the rare earth ion solution to form the fiber core layer 10 doped with rare earth ions.
Specifically, S20 further includes:
firstly, taking down a substrate tube, soaking the substrate tube into a rare earth ion solution, and taking out the substrate tube after soaking for a certain time;
the loose layer after being immersed in the rare earth ion solution is then dried, oxidized and vitrified in order to form the rare earth ion doped core layer 10.
S30, the base tube is fused and contracted in a first temperature range to form the optical fiber preform.
Specifically, S30 further includes:
the substrate tube with the deposited core layer 10 is collapsed at a first temperature range to form a solid optical fiber preform.
S40, performing quartz tube sleeving on the optical fiber preform rod according to a fixed core-to-cladding ratio after testing to form a sleeve rod.
Specifically, S40 further includes:
the optical fiber preform and the high-purity quartz sleeve are subjected to high-temperature fusion shrinkage according to a fixed core-cladding ratio to form a sleeve rod, and an inner cladding 20 is formed around the fiber core layer 10, and the inner cladding 20 completely wraps the fiber core layer 10.
And S50, vertically drilling holes in the inner cladding 20 area in the sleeve rod along the axial direction, and polishing the inner wall of the holes to form the first through holes 201.
Specifically, S50 further includes:
drilling holes vertically or obliquely along the cylindrical meridian plane at any position in the cladding region (inner cladding 20 region) of the ferrule rod without damaging the core layer 10, and then polishing the inner wall of the holes to form the first via holes 201.
S60, filling the first via hole 201 with a low refractive index material, and performing drawing, rotation and coating treatments on the ferrule rod filled with the low refractive index material, respectively, to form the axial absorption graded optical fiber 100.
The first via hole 201 is filled with a low refractive index material, and then the ferrule rod and the low refractive index material are put into a drawing tower together for wire forming and coating, and the rotation speed is controlled to adjust the spiral period of the low refractive index material, so that the axial absorption graded optical fiber 100 is prepared.
The technical scheme of the present application will now be described with reference to specific embodiments.
Example 1:
referring to fig. 1, fig. 1 is an end-face schematic diagram of an axial absorption graded optical fiber 100 according to embodiment 1 of the present application; the axial absorption gradient optical fiber 100 provided by the embodiment of the application comprises a fiber core layer 10, an inner cladding layer 20 and a coating layer 30 which are sequentially arranged from inside to outside along the radial direction, wherein the inner cladding layer 20 is only embedded with one cladding layer unit 40, the cladding layer unit 40 and the fiber core layer 10 are spirally wound, and the screw pitch is gradually changed along the axial direction;
wherein, the refractive index of the fiber core layer 10 is larger than the refractive index of the inner cladding layer 20, the refractive index of the inner cladding layer 20 is larger than the refractive index of the cladding unit 40, and the refractive index of the cladding unit 40 is larger than the refractive index of the coating layer 30.
Specifically, the cladding elements 40 are axially equidistant from the core 10.
Specifically, the core layer 10 includes a matrix layer and a rare earth oxide layer completely surrounding the matrix layer, and the matrix layer is made of SiO 2 The material of the rare earth oxide layer comprises Yb 2 O 3 、Er 2 O 3 Tm of 2 O 3 At least one of (a) and (b); specifically, the inner cladding 20 is composed of a matrix SiO 2 The coating layer 30 is composed of acrylic resin; the material of the cladding unit 40 is fluorine-doped or boron-doped SiO 2
Referring to fig. 2, fig. 2 is a schematic longitudinal structural diagram of an axial absorption graded optical fiber 100 according to embodiment 1 of the present application; at this time, the axial absorption graded optical fiber 100 includes only the first pumping end, and the first pitch L1 corresponding to the repeated twisting period of the cladding unit 40 is gradually reduced in the direction (first direction D1) away from the first pumping end.
Wherein the cladding unit 40 is spirally wound around the core layer 10, the first pitch L1 thereof is gradually reduced along the first direction D1, and the reflection frequency of the pump light is increased, so that the pump absorption of the axial absorption graded-mode fiber 100 is gradually increased along the axial direction, thereby alleviating the laser thermal effect in the single-end pumped fiber laser.
Referring to fig. 3, fig. 3 is a schematic view illustrating another longitudinal structure of an axial absorption graded optical fiber 100 according to embodiment 1 of the present application; at this time, the axial absorption graded optical fiber 100 includes a second pump end and a third pump end, and the second pitch L2 corresponding to the repeated twisting period of the cladding unit 40 is gradually decreased and then gradually increased along the direction (second direction D2) away from the second pump end or the third pump end.
Wherein the cladding unit 40 is spirally wound around the core layer 10, the second pitch L2 thereof is decreased first and then increased in the second direction D2, and the reflection frequency of the pump light is increased first and then decreased, so that the pump absorption of the axial absorption graded optical fiber 100 is increased first and then decreased in the axial direction, thereby alleviating the laser heating effect in the double-end pumped fiber laser.
In embodiment 1 of the present application, the preparation method of the axial absorption graded optical fiber 100 includes the steps of:
(1) A high-purity quartz tube with the length of 500mm, the outer diameter of 25mm and the wall thickness of 3mm is adopted as a substrate tube, and SF with the flow of 100sccm is introduced at 2000-2100 DEG C 6 Polishing and etching the inner wall of the substrate tube by gas, and then introducing SiCl with the flow of 200sccm 4 O of 500sccm 2 And 100sccm He, setting the heating temperature to 1500-1600 ℃ to promote the mixed gas to react and deposit SiO on the inner wall of the substrate tube 2 A porous loose layer of material;
(2) Removing the substrate tube deposited with loose layer, and soaking in YbCl solution 3 、ErCl 3 、TmCl 3 Soaking in one or more rare earth ion solutions for 1 hr, taking out the substrate tube, and introducing 1000sccm N into the tube for 0.5 hr 2 Drying the moisture in the loose layer;
(3) 300sccm of Cl was introduced into the substrate tube 2 Setting the heating temperature to 1000-1200 ℃, dehydrating and drying the loose layer, and then introducing 800sccm of O 2 And raising the temperature to 1300-1400 ℃, oxidizing rare earth ions adsorbed on the loose layer, raising the temperature to 2000-2100 ℃, and performing high-temperature vitrification sintering on the loose layer to obtain a fiber core layer 10 doped with the rare earth ions;
(4) Repeatedly heating the substrate tube at a high temperature of 2000-2100 ℃ for a plurality of times until the substrate tube is fused and contracted into an optical fiber preform;
(5) Performing fiber core diameter and outer diameter test on the optical fiber preform, wherein the fiber core diameter and the outer diameter are respectively 2mm and 15mm, then matching the fiber core with a certain high-purity quartz sleeve according to a fixed core-to-cladding ratio of 0.05-0.10, and performing high-temperature fusion shrinkage at 2000-2100 ℃ to form a sleeve rod with the outer diameter of 20-40 mm;
(6) Referring to fig. 4, fig. 4 is a schematic diagram of drilling a casing rod according to embodiment 1 of the present application; wherein, an inner hole with the diameter of 4-6 mm is vertically drilled at any position 5mm away from the center of the fiber core layer 10 in the region where the inner cladding 20 of the sleeve rod is positioned along the axial direction, and the inner wall of the hole is polished to form a first via hole 201;
(7) A fluorine-doped rod or a boron-doped rod with the outer diameter equivalent to the inner hole diameter and lower than the refractive index of pure quartz is plugged into the first via hole 201 of the sleeve rod, then the fluorine-doped rod or the boron-doped rod is placed into a wire drawing tower to be melted into wires and coated at the high temperature of 2000-2100 ℃, the wire drawing speed is controlled to be 1-20 m/min, a chuck for clamping the sleeve rod rotates along with wire drawing, the rotating speed is continuously changed in a reciprocating way and a reciprocating way at 100-1000 r/min, and the repeated torsion period of the structure of the cladding unit 40 with the low refractive index is controlled to be 0.01-1 m, so that the axial absorption gradient optical fiber 100 is prepared.
Example 2:
unlike the end face structure of the axial absorption gradient optical fiber 100 provided in example 1, the axial absorption gradient optical fiber 100 provided in example 2 has two second cladding units 40 of low refractive index.
Referring to fig. 5, fig. 5 is an end view of an axial absorption graded optical fiber 100 according to embodiment 2 of the present application; the axial absorption gradient optical fiber 100 provided by the embodiment of the application comprises a fiber core layer 10, an inner cladding layer 20 and a coating layer 30 which are sequentially arranged from inside to outside along the radial direction, wherein the inner cladding layer 20 is only embedded with two cladding units 40, the cladding units 40 and the fiber core layer 10 are spirally wound, and the screw pitch is gradually changed along the axial direction;
wherein, the two cladding units 40 are symmetrically arranged with respect to the fiber core layer 10; the refractive index of the core layer 10 is greater than the refractive index of the inner cladding layer 20, the refractive index of the inner cladding layer 20 is greater than the refractive index of the cladding unit 40, and the refractive index of the cladding unit 40 is greater than the refractive index of the coating layer 30.
Specifically, the axial absorption graded optical fiber 100 includes only the first pumping end, and the third pitch L3 corresponding to the repeated twisting period of the two cladding units 40 is gradually reduced in the direction away from the first pumping end (third direction D3).
Specifically, the cladding elements 40 are axially equidistant from the core 10.
Example 2 of the present application also provides a method for producing the axial absorption graded optical fiber 100 described above, which is different from the method for producing example 1 in that step (6): as shown in fig. 6 to 7, fig. 6 is a schematic view of a casing rod drilling in embodiment 2 of the present application; fig. 7 is a schematic view showing the longitudinal structure of the axial absorption gradient optical fiber 100 in embodiment 2 of the present application;
specifically, in step (6), the method for manufacturing the axial absorption graded optical fiber 100 according to embodiment 2 of the present application needs to drill holes vertically at symmetrical positions on both sides of the core layer 10. Other preparation steps were consistent with the preparation method of example 1 of the present application, and finally an axial absorption graded optical fiber 100 as shown in fig. 7 was obtained.
Specifically, the axial absorption graded fiber 100 provided in embodiment 2 of the present application aims to increase the number of cladding units 40 with low refractive index to enhance the reflection frequency of the pump light, so as to increase the overall pump absorption of the axial absorption graded fiber 100 and the pump absorption gap at different axial positions.
Example 3:
unlike the end face structure of the axial absorption gradient optical fiber 100 provided in example 2, the interval between the two low refractive index cladding units 40 and the core layer 10 in the axial absorption gradient optical fiber 100 provided in example 3 has a gradient trend in the axial direction.
Referring to fig. 8, fig. 8 is an end view of an axial absorption gradient optical fiber 100 according to embodiment 3 of the present application; the axial absorption gradient optical fiber 100 provided by the embodiment of the application comprises a fiber core layer 10, an inner cladding layer 20 and a coating layer 30 which are sequentially arranged from inside to outside along the radial direction, wherein the inner cladding layer 20 is only embedded with two cladding units 40, the cladding units 40 and the fiber core layer 10 are spirally wound, and the screw pitch is gradually changed along the axial direction;
wherein, the two cladding units 40 are symmetrically arranged about the fiber core layer 10, and the interval between the two cladding units 40 with low refractive index and the fiber core layer 10 is gradually changed along the axial direction; the refractive index of the core layer 10 is greater than the refractive index of the inner cladding layer 20, the refractive index of the inner cladding layer 20 is greater than the refractive index of the cladding unit 40, and the refractive index of the cladding unit 40 is greater than the refractive index of the coating layer 30.
Specifically, referring to fig. 10, fig. 10 is a schematic longitudinal structural diagram of an axial absorption graded optical fiber 100 in embodiment 3 of the present application; the axial absorption graded optical fiber 100 includes only the first pumping end, and the fourth pitch L4 corresponding to the repeated twisting period of the two cladding units 40 gradually increases along the direction (fourth direction D4) approaching the first pumping end.
Further, as shown in fig. 8, in the first end face 101 of the axial absorption graded optical fiber 100 (the first end face 101 is further away from the first pumping end), the spacing between the two low refractive index cladding units 40 and the core layer 10 is w1; in the second end face 102 of the axial absorption graded optical fiber 100 (the second end face 102 is closer to the first pumping end), the distance between the two low refractive index cladding units 40 and the core layer 10 is w2, and w2 is larger than w1; at this time, the intervals between the two low refractive index cladding units 40 and the core layer 10 gradually increase in the fourth direction D4.
Example 3 of the present application also provides a method for producing the axial absorption graded optical fiber 100 described above, which is different from the method for producing example 1 in that step (6): as shown in fig. 9 to 10, fig. 9 is a schematic view of a casing rod drilling in embodiment 3 of the present application; fig. 10 is a schematic view showing the longitudinal structure of the axial absorption gradient optical fiber 100 in embodiment 3 of the present application.
Specifically, as shown in fig. 9, in step (6), in the method for manufacturing the axial absorption graded optical fiber 100 according to embodiment 3 of the present application, first vias 201 are required to be vertically drilled at symmetrical positions on both sides of the core layer 10 and at an angle of 2-5 ° with respect to the central axis. Other preparation steps were consistent with the preparation method of example 1 of the present application, and finally an axial absorption graded optical fiber 100 as shown in fig. 10 was obtained.
Specifically, the axial absorption graded fiber 100 provided in embodiment 3 of the present application is intended to shorten the reflection path of the pump light to enhance the reflection frequency of the pump light, thereby increasing the overall pump absorption of the axial absorption graded fiber 100 and the pump absorption gap at axially different positions.
Compared with the prior art, the axial absorption graded optical fiber 100 provided by the application has the following advantages:
firstly, the axial absorption graded optical fiber 100 provided by the application influences the reflection frequency of pump light at different axial positions by changing the spiral period of the cladding unit 40 with low refractive index, so that the axial distribution of the absorption coefficient of the optical fiber pump is optimized, the heat generation of the optical fiber is further reduced, and the output power of the optical fiber laser is finally improved;
secondly, the axial absorption graded optical fiber 100 provided by the application modifies the inner cladding 20 by inserting the low refractive index unit, thereby not only effectively solving the defect that spiral light and a fiber core are difficult to meet in a round optical fiber, but also reducing the effective reflection area of pump light in the inner cladding 20, shortening the reflection path of the pump light, and improving the reflection frequency of the inner cladding 20, so as to improve the pump absorption coefficient of the optical fiber;
thirdly, the axial absorption gradient optical fiber 100 provided by the application adopts a round cladding design, which is beneficial to the welding between the active optical fiber and the passive optical fiber and better geometric control, and can avoid the welding loss of the traditional special-shaped optical fiber and the round optical fiber;
fourth, the preparation method of the axial absorption gradient optical fiber 100 provided by the application is simple, can realize the regulation and control of parameters in the preparation process through automatic equipment, and is suitable for large-scale production.
Fifth, according to the axial absorption gradient optical fiber 100 and the preparation method thereof provided by the application, the novel structure of the inner cladding 20 is designed to replace the fiber core rare earth ion concentration distribution regulation and control, so that the preparation difficulty of the optical fiber is remarkably reduced.
In summary, unlike the prior art, the present application provides an axial absorption graded optical fiber 100 and a preparation method thereof, wherein the axial absorption graded optical fiber 100 comprises a core layer 10, an inner cladding layer 20 and a coating layer 30 sequentially arranged from inside to outside along a radial direction, at least one cladding layer unit 40 is embedded in the inner cladding layer 20, the cladding layer unit 40 and the core layer 10 are spirally wound and the thread pitch is in a graded trend along the axial direction, wherein the refractive index of the core layer 10 is greater than that of the inner cladding layer 20, the refractive index of the inner cladding layer 20 is greater than that of the cladding layer unit 40, and the refractive index of the cladding layer unit 40 is greater than that of the coating layer 30; according to the axial absorption gradient optical fiber 100 provided by the application, at least one cladding unit 40 with a lower refractive index is embedded in the inner cladding 20, the cladding unit 40 and the fiber core layer 10 are spirally wound and the screw pitch is in a gradient trend along the axial direction, so that the defect that spiral rotation in the axial absorption gradient optical fiber 100 is difficult to be intersected with the fiber core layer 10 is effectively overcome, meanwhile, the effective reflection area of pump light in the inner cladding 20 is reduced, the reflection path of the pump light is shortened, and the reflection frequency of the inner cladding 20 is improved, so that the pump absorption coefficient of the axial absorption gradient optical fiber 100 is improved, and the problem of uneven heat distribution of the axial absorption gradient optical fiber 100 in the axial direction is further improved; meanwhile, the preparation method is simple, the adjustment and control of the absorption coefficient of the pump in the preparation process can be realized through automatic equipment, and the stability is good.
It should be noted that, the foregoing embodiments all belong to the same inventive concept, and the descriptions of the embodiments have emphasis, and where the descriptions of the individual embodiments are not exhaustive, reference may be made to the descriptions of the other embodiments.
The foregoing examples merely illustrate embodiments of the application and are described in more detail and are not to be construed as limiting the scope of the application. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the application, which are all within the scope of the application. Accordingly, the scope of protection of the present application is to be determined by the appended claims.

Claims (10)

1. The axial absorption gradient optical fiber is characterized by comprising a fiber core layer, an inner cladding layer and a coating layer which are sequentially arranged from inside to outside along the radial direction, wherein at least one cladding unit is embedded in the inner cladding layer, the cladding unit and the fiber core layer are spirally wound, and the screw pitch is gradually changed along the axial direction;
the refractive index of the fiber core layer is larger than that of the inner cladding layer, the refractive index of the inner cladding layer is larger than that of the cladding layer unit, and the refractive index of the cladding layer unit is larger than that of the coating layer.
2. The axial absorption graded optical fiber of claim 1, wherein the axial absorption graded optical fiber comprises only a first pumping end, and the pitch corresponding to the repeated twisting period of the cladding unit is gradually reduced in a direction away from the first pumping end.
3. The axial absorption graded optical fiber of claim 1, wherein the axial absorption graded optical fiber comprises a second pumping end and a third pumping end, and the pitch corresponding to the repeated twisting period of the cladding unit is gradually reduced and then gradually increased along the direction away from the second pumping end or the third pumping end.
4. An axial absorption gradient optical fiber according to claim 2 or 3, wherein the repeat twist period of the cladding unit is in the range of 0.01m to 1m.
5. An axial absorption gradient fiber according to claim 2 or 3, wherein the axial absorption gradient fiber comprises two cladding units, the two cladding units being symmetrically arranged about the core layer.
6. The axial absorption gradient fiber according to claim 5, wherein the spacing between the two cladding units and the core layer has a gradient trend along the axial direction.
7. The axial absorption gradient optical fiber according to claim 1, wherein the core layer comprises a matrix layer and a rare earth oxide layer completely surrounding the matrix layer, and the matrix layer is made of SiO 2 The material of the rare earth oxide layer comprises Yb 2 O 3 、Er 2 O 3 Tm of 2 O 3 At least one of (a) and (b); the material of the inner cladding is SiO 2 The method comprises the steps of carrying out a first treatment on the surface of the The cladding unit is made of SiO doped with fluorine or boron 2
8. A method of making an axially absorbing graded fiber as claimed in any one of claims 1 to 7, comprising:
s10, etching the inner wall of a base pipe, and forming a loose layer on the inner wall of the base pipe;
s20, taking down the base pipe, soaking the base pipe in a rare earth ion solution, and sequentially carrying out oxidation and vitrification treatment on the loose layer soaked by the rare earth ion solution to form a fiber core layer doped with rare earth ions;
s30, melting and shrinking the base tube in a first temperature range to form an optical fiber preform;
s40, performing quartz tube sleeving on the optical fiber preform rod according to a fixed core-to-cladding ratio after testing to form a sleeving tube rod;
s50, vertically drilling holes in the inner cladding region in the sleeve rod along the axial direction, and polishing the inner wall of the holes to form first through holes;
and S60, filling a low-refractive-index material into the first via hole, and respectively carrying out wiredrawing, rotation and coating treatment on the sleeve rod filled with the low-refractive-index material to form the axial absorption graded optical fiber.
9. The method for preparing an axial absorption graded optical fiber according to claim 8, wherein the step S60 specifically comprises:
s601, placing the sleeve rod in a wire drawing tower, and clamping the sleeve rod by using a chuck;
s602, melting and forming filaments on the sleeve rod in a second temperature range, and coating the filaments, and simultaneously rotating the chuck to form the axial absorption gradient optical fiber.
10. The method for manufacturing an axially absorbing graded optical fiber according to claim 9, wherein the drawing speed of the ferrule rod for melt-spinning is 1-20 m/min, and the rotation speed of the chuck is 100-1000 r/min.
CN202310861758.3A 2023-07-14 2023-07-14 Axial absorption gradual change optical fiber and preparation method thereof Active CN116594101B (en)

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CN114300917A (en) * 2021-11-16 2022-04-08 武汉睿芯特种光纤有限责任公司 High-power side-pumped active optical fiber
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JP2003229618A (en) * 2002-02-05 2003-08-15 Mitsubishi Cable Ind Ltd Double clad fiber and production method therefor
US20070104436A1 (en) * 2005-10-20 2007-05-10 Ming-Jun Li High numerical aperture optical fiber
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