JP7332706B2 - Photonic crystal fiber preform, manufacturing method thereof, and photonic crystal fiber - Google Patents

Description

The present invention is in the fields of optics and laser optoelectronics, and more particularly relates to photonic crystal fibers, their preforms and methods of manufacture.

With the rapid development of fiber lasers in recent years, how to improve the laser output power is one of the research focal points, and nonlinear effects and thermal damage are the bottlenecks for achieving further breakthroughs in optical output power. One of the key ways to solve these two problems is to increase the core diameter of the optical fiber, but without sacrificing the absorption coefficient and conversion efficiency of the cladding, while significantly degrading the beam quality. ytterbium-doped photonic crystal fibers are produced. The coating layer of a photonic crystal fiber in the traditional sense is often composed of periodically arranged air holes.

However, these periodically arranged air holes can pose two problems. First, there is a problem that the refractive index of the coating layer is lowered and the refractive index difference between the core and the coating layer is too large. Second, the capillaries forming the air holes are prone to collapse during wire drawing, resulting in low yield and poor beam output quality. At the same time, the heat conduction performance of air is common, and the difficulty of heat management is high in high-power usage scenes.

SUMMARY OF THE INVENTION In response to the above-mentioned deficiencies or improvement needs of the prior art, the present invention provides a photonic crystal fiber, its preform, its method of manufacture and use, for the purpose of which the air is Substitute holes to form high-quality, tunable refractive index, high-yield photonic crystal fibers, whose high power, single-cavity low-loss, and high-beam-quality energy transmission make quality control impossible in the prior art. Overcoming the technical problems of too large a refractive index difference between the core and the cladding layers and difficult thermal management at high power.

To achieve the above objects, according to one aspect of the present invention, there is provided a photonic crystal fiber preform for forming a glass filament for forming a core and a fluorine-doped unit for an inner coating layer. a glass filament for, a glass casing of an inner covering layer, and a glass casing of an outer covering layer. A glass filament for forming the core has a relative refractive index difference Δ1 of 0.08% to 0.09% and a diameter of 1 to 4 mm. The glass filament for forming the fluorine-doped unit of the inner coating layer has the same outer diameter as the glass filament for forming the core, and the coating layer and the relative refractive index difference Δ2 are -0.14% to - a core layer of 0.82%, said coating layer being the same material as the casing material of said inner coating layer, f = _dF / _d1 , where _dF is the inner coating represents the coating layer inner diameter of the glass filaments for forming the fluoridated units of the layer, and _d1 represents the coating layer outer diameter of the glass filaments for forming the fluoridated units of the inner coating layer). The duty ratio f of the fluorine addition unit is 0.085 to 0.09. The glass casing of the inner coating layer has a thickness of 2 mm to 20 mm and a relative refractive index difference Δ3 of 0.08% to 0.1%. The glass casing of the outer covering layer has a thickness of 30 mm to 90 mm and is a pure silica glass tube. The glass casing of the inner cladding layer and the glass casing of the outer cladding layer are concentric nested structures, the glass filament for forming the core is in the center of the glass casing of the inner cladding layer, and the glass casing of the inner cladding layer is positioned between the glass filaments for forming the core and the inner cladding layer casing.

Preferably, in the photonic crystal fiber preform, the glass casing of the inner coating layer has an inner diameter of 22 to 37.5 mm and an outer diameter of 45 to 50 mm, and the inner diameter Between the outer diameter of the glass filament of the addition unit and the number of layers, _{1 in} D = 2n ₁ * d ₁ , n _≥ 4 and 1 mm ≤ d ₁ ≤ 4 mm (where _{1 in} D is the inner coating layer , _n1 indicates the number of glass filament layers of the fluoridated unit of the inner coating layer, and _d1 is the outer diameter of the glass filaments for forming the fluoridated unit of the inner coating layer. ). Preferably, the glass casing of the outer covering layer has an inner diameter of 50-60 mm and an outer diameter of 80-150 mm.

Preferably, in the photonic crystal fiber preform, the glass filaments of the fluorine-doped unit are densely arranged in an array around a core glass filament positioned at the center of the array, and the glass filaments for forming the core and the number of glass filaments for forming the fluorine-added unit is 0.5 to 3:12, preferably 1:12, 7:120, 7:162, 19:84, 19:120. , or 19:162.

Preferably, in the photonic crystal fiber preform, the inner wall of the glass casing of the outer coating layer has a low refractive index layer, and the low refractive index layer is a densely arranged capillary glass tube or a low refractive index layer. a refractive index glass material layer, wherein the capillary glass tube has an inner diameter of 2-4 μm, an outer diameter of 2.5-5 mm, and is sealed at both ends; It has a refractive index of 1.22 to 1.25.

According to another aspect of the present invention, there is provided a method of manufacturing the photonic crystal fiber preform, comprising the following steps.
(1) Glass filaments for forming a fluorine-added unit and glass filaments for forming a core are stacked in a predetermined number in a regular hexagonal shape using a mold and bundled into a glass filament bundle to form the core. center the glass filament.
(2) The glass filament bundles obtained in step (1) are formed into a concentric nest structure with an inner casing and an outer casing.
Preferably, the glass filament for forming the core has a rare earth-doped core layer deposited in the liner so that the relative refractive index difference Δ1 of the core layer is 0.08% to 0.1%, and the liner is Manufactured by removing and drawing.
The glass filament for forming the fluorine-doped unit deposits the inner coating layer material in the liner to a preset thickness, and then the relative refractive index difference Δ2 of the fluorine-doped glass layer is from −0.14% to It is manufactured by depositing a fluorine-added glass layer to -0.82%, removing the liner, and drawing.

Preferably, in the method for manufacturing a photonic crystal fiber preform, when the inner wall of the glass casing of the outer coating layer has a densely arranged capillary glass tube, the capillary glass tube is a pure silica casing. It is manufactured by drawing a capillary tube with a predetermined outer diameter in equal proportions and sealing both ends of the capillary tube with a flame. When the inner wall of the glass casing of said outer cladding layer has a layer of low refractive index glass material, said outer cladding layer is manufactured by depositing a fluorinated layer within a pure silica liner.

According to another aspect of the invention, a photonic crystal fiber is provided and includes a core, an inner cladding layer, and an outer cladding layer. The core has a relative refractive index difference Δ1 of 0.08% to 0.1% and a diameter of 40 to 50 μm. The inner coating layer includes a background layer having a diameter of 200 to 400 μm and a relative refractive index difference Δ3 of 0.08% to 0.1%, and an array of and a fluorine-doped unit having a relative refractive index difference Δ2 of −0.14% to −0.82%. The outer coating layer has a diameter of 800 μm to 1000 μm.

Preferably, in the photonic crystal fiber, the fluorine-doped unit is distributed in a region of the inner coating layer where the thickness to the core is 1/5 to 1/2 of the thickness of the inner coating layer, Its diameter is 1-1.4 μm and the center-to-center distance of said fluorinated units is 11.5-16 μm.

Preferably, in said photonic crystal fiber, said core is a silica layer co-doped with ytterbium, aluminum and phosphorus. Preferably, the outer coating layer includes a pure silica layer and a low refractive index layer, and the low refractive index layer is located on the innermost surface of the outer coating layer and has a refractive index or equivalent refractive index of 1.22 to 1.25 and consists of circumferentially arranged air holes or layers of low refractive index glass material.

According to another aspect of the invention, there is provided the use of said photonic crystal fiber to function as a gain medium.

By adjusting the refractive index of the core, the refractive index of the fluorinated unit of the inner cladding layer, the geometry of the fluorinated unit, and the geometry of the air cladding layer, the present invention provides a high absorption of the optical fiber for the excitation light, In addition, it can be converted into signal light in a desired wavelength band, has an extremely large mode field area, and has excellent beam quality.

1 is a schematic diagram of a preform of a double-coated ytterbium-doped photonic crystal fiber according to Example 1 of the present invention; FIG. 1 is a schematic cross-sectional view of a double-layer-type ytterbium-doped photonic crystal fiber according to Example 1 of the present invention; FIG. FIG. 2 is a single-mode operating range graph of the ytterbium-doped double-layer photonic crystal fiber according to Example 1 of the present invention; FIG. FIG. 2 is a schematic diagram of a preform of a double-coated ytterbium-doped photonic crystal fiber according to Example 2 of the present invention; FIG. 2 is a schematic cross-sectional view of a double-coated ytterbium-doped photonic crystal fiber according to Example 2 of the present invention; FIG. 5 is a single-mode operating range graph of the ytterbium-doped double-layer photonic crystal fiber according to Example 2 of the present invention; FIG. 1 is a schematic diagram of a test platform for an all-solid double-layered ytterbium-doped photonic crystal fiber used in Examples 1 and 2 of the present invention; FIG. FIG. 2 is an output spot diagram of a double-coated ytterbium-doped photonic crystal fiber according to Examples 1 and 2 of the present invention;

In order to make the purpose, technical means and advantages of the present invention clearer, the present invention will be described in more detail below with reference to examples. It should be understood that the specific examples described herein are merely illustrative of the invention and are not intended to be limiting of the invention. The technical features according to the embodiments of the present invention described below can be combined with each other as long as they do not contradict each other.

The present invention provides a photonic crystal fiber preform comprising a glass filament for forming a core, a glass filament for forming a fluoridated unit of an inner cladding layer, a glass casing for an inner cladding layer, and an outer core. and a glass casing of the covering layer. Here, the glass filament for forming the core has a relative refractive index difference Δ1 of 0.08% to 0.1% and a diameter of 1 to 4 mm, preferably 2 to 2.5 mm, The core formed has a diameter of 3 to 6.5 mm.

The glass filament for forming the fluorine-doped unit of the inner coating layer has the same outer diameter as the glass filament for forming the core, and the coating layer and the relative refractive index difference Δ2 are -0.14% to - a core layer that is 0.82%. The material of the coating layer is the same as the material of the casing of the inner coating layer, which is the background material, and the outer diameter of the coating layer is 1-4 mm. Preferably, f = d _F /d ₁ (where d _F represents the coating layer inner diameter of the glass filament for forming the fluoridation unit of the inner coating layer, and d ₁ is the fluorination unit of the inner coating layer The duty ratio f of the fluoridation unit calculated by (indicating the outer diameter of the coating layer of the glass filament for forming the ) is 0.085 to 0.09. The diameter of the formed inner coating layer portion is 45-50 mm.

The glass casing of the inner coating layer has a thickness of 2 mm to 20 mm, and its inner diameter has the following relationship between the outer diameter of the glass filament of the fluoridation unit of the inner coating layer and the number of layers.
_{1 in} D = 2n ₁ * d ₁ , n ₁ ≥ 4 and 1 mm ≤ d ₁ ≤ 4 mm
Here, _{1 in} D indicates the inner diameter of the glass casing of the inner coating layer, n ₁ indicates the number of glass filament layers of the fluoridation unit of the inner coating layer, and d ₁ indicates the number of layers of the inner coating layer. 3 shows the outer diameter of the glass filament of the fluoridation unit.

The outer diameter of the glass casing of the inner coating layer is the inner coating layer diameter of the optical fiber, the core diameter of the optical fiber, the number of layers of ytterbium-doped glass filament to form the core, and the low refractive index to form the inner coating layer. The ratio has the following relationship with the outer diameter of the fluoridation unit.
D _{outside 1} = (D ₆ /D ₄ )(2n ₂ -1) d ₁ , 40 μm≦D ₄ ≦50 μm
where Dout ₁ denotes the outer diameter of the glass casing of the inner cladding layer, D ₆ denotes the diameter of the inner cladding layer of the optical fiber, D ₄ denotes the core diameter of the optical fiber, _n2 indicates the number of layers of ytterbium-doped glass filaments to form the core.

The relative refractive index difference Δ3 of the background material for forming said inner coating layer is between 0.08% and 0.1%, preferably Ge-doped silica.

The glass casing of the outer coating layer has a thickness of 30 mm to 90 mm, and its outer diameter is determined by the outer diameter of the optical fiber, the core diameter of the optical fiber, the number of layers of ytterbium-doped glass filament for forming the core, the inner It has the following relationship with the outer diameter of the low refractive index fluorine-doped unit for forming the coating layer.
D _{out 2} = (D ₅ /D ₄ )(2n ₂ −1) d ₁ , 800 μm≦D ₅ ≦1000 μm
Here, _D5 indicates the outer diameter of the optical fiber.

The inner wall of the glass casing of the outer covering layer has a low refractive index layer, and the low refractive index layer is a densely arranged capillary glass tube or a low refractive index glass material layer. The inner diameter has the following relationship with the outer diameter of the glass casing forming the inner coating layer.
D _{outside 2} =D _{outside 1} +2d ₂
where _d2 denotes the low refractive index thickness of the outer coating layer.

When the low refractive index layer is a densely arranged capillary glass tube, the glass casing of the outer coating layer has an inner diameter of 50 to 60 mm and an outer diameter of 80 to 150 mm, and the capillary is It has an outer diameter of 2.5 mm to 5 mm, an inner diameter of 2 mm to 4 μm, and is sealed at both ends.

When the low refractive index layer is a low refractive index glass material layer, the glass casing of the outer coating layer has an inner diameter of 50 to 60 mm and an outer diameter of 80 to 150 mm, and the low refractive index glass material layer is It has an outer diameter of 60 to 100 mm and an equivalent refractive index of 1.22 to 1.25.

The glass casing of the inner cladding layer and the glass casing of the outer cladding layer are concentric nested structures, the glass filament for forming the core is in the center of the glass casing of the inner cladding layer, and the glass casing of the inner cladding layer is positioned between the glass filaments for forming the core and the inner cladding layer casing. The number ratio of the glass filaments for forming the core and the number of glass filaments for forming the fluorinated units is 0.5 to 3:12, preferably 1:12, 7:120, 7: 162, 19:84, 19:120, or 19:162.

A photonic crystal preform according to the invention can be made into a photonic crystal fiber according to the invention by a drawing process.

A method for manufacturing a photonic crystal fiber preform according to the present invention includes the following steps.

(1) Glass filaments for forming a fluorine-added unit and glass filaments for forming a core are stacked in a predetermined number in a regular hexagonal shape using a mold and bundled into a glass filament bundle to form the core. center the glass filament.

The glass filament for forming the core is prepared by depositing a rare earth-doped core layer in the liner and removing the liner so that the relative refractive index difference Δ1 of the core layer is 0.08% to 0.1%. Manufactured by wire drawing. The ytterbium-doped core is preferably deposited in a pure silicon liner using an MCVD CDS (Rare Earth Chelate Vapor Deposition) process.

A glass filament for forming said fluorine-doped unit deposits an inner coating layer material, preferably germanium-doped glass, in the liner to a preset thickness, and then the relative refractive index difference Δ2 of the fluorine-doped glass layer is It is manufactured by depositing a fluorine-added glass layer so as to have a concentration of -0.14% to -0.82%, removing the liner, and drawing. Preferably, a PCVD process is used to deposit the germanium-doped inner cladding layer material and the fluorine-doped glass layer within the pure silicon liner.

(2) The glass filament bundles obtained in step (1) are formed into a concentric nest structure with an inner casing and an outer casing.

When the inner wall of the glass casing of the outer coating layer has closely arranged capillary glass tubes, the capillary glass tubes draw the pure silica casing into capillaries of a predetermined outer diameter in equal proportions, and both ends of the capillaries is sealed with a flame. When the inner wall of the glass casing of the outer cladding layer has a layer of low refractive index glass material, the outer cladding layer is deposited by depositing a fluorine-doped layer into the liner and, after deposition is completed, melt shrinkage with the pure silica casing. Manufactured by

A photonic crystal fiber according to the present invention includes a core, an inner cladding layer and an outer cladding layer. Here, the core has a relative refractive index difference Δ1 of 0.08% to 0.1% and a diameter of 40 μm to 50 μm. The core is preferably silica doped with ytterbium, aluminum and/or phosphorus.

ここで、ｎ_ｃｏｒｅは、コアの屈折率であり、ｎ_ｓｉは、純ケイ素の屈折率である。 The relative refractive index difference Δ1 of the core is calculated as follows.

where n _core is the refractive index of the core and n _si is the refractive index of pure silicon.

The inner coating layer has a diameter of 200 μm to 400 μm and comprises a background material and fluorinated units periodically arranged in the background material. In the inner coating layer, the fluorine-added units are distributed in a region where the thickness to the core is 1/5 to 1/2 of the thickness of the inner coating layer. The background material has a refractive index difference Δ3 of 0.08% to 0.1%, and the fluorine-doped unit is a glass material having a relative refractive index difference Δ2 of −0.14% to −0.82%. is.

ここで、ｎ_Ｆは、フッ素添加ユニットの屈折率であり、ｎ_ｓｉは、純ケイ素の屈折率である。 The relative refractive index difference Δ2 of the fluorine-doped unit is calculated as follows.

where _nF is the refractive index of the fluorinated unit and _nsi is the refractive index of pure silicon.

ここで、ｎ_ＧＥは、バックグラウンド材料の屈折率であり、ｎ_ｓｉは、純ケイ素の屈折率である。 The refractive index difference Δ3 of the background material is calculated as follows.

where n _GE is the refractive index of the background material and n _si is the refractive index of pure silicon.

The fluorine-doped units are distributed in a region of 80 μm to 115 μm of the inner coating layer, have a diameter of 1.2 μm to 1.5 μm, a number of 7 to 19, and a center-to-center distance of 12 to 18 μm.

The outer coating layer has an equivalent refractive index of 1.22 to 1.25 and a diameter of 800 μm to 1000 μm. The outer coating layer comprises a low refractive index layer which is periodically arranged air holes or a low refractive index glass material with a refractive index of 1.22-1.25 and a diameter of 800-1000 μm.

The core has a diameter of 40-50 μm and an outer diameter of 800 μm-1 mm.

The photonic crystal fiber according to the present invention can withstand high-power lasers due to the ultra-large mode-field area of the core, and its coated waveguide structure allows the optical fiber to be single-mode on the premise of a large mode-field area. It can support transmission and has high beam quality. Its ultra-large inner cladding numerical aperture enables the fiber to absorb higher power pump light and is therefore suitable for the field of high power fiber lasers. The photonic crystal fiber according to the present invention, whose inner cladding layer periodic unit is all-solid, has a higher optical fiber yield and lower production cost compared to conventional air-hole technology. Overall, the photonic crystal fiber according to the invention is suitable for high power, single cavity low loss, high beam quality energy transmission and as a gain medium.

Examples are given below.

(Example 1)
A photonic crystal fiber preform, as shown in FIG. an outer casing 5; Here, the core is formed by stacking seven ytterbium-doped glass filaments in a regular hexagon, and has a relative refractive index difference of Δ1=0.085% and an outer diameter of 2 mm. The inner coating layer is composed of four layers in which 84 fluorine-doped glass filaments are deposited in a regular hexagon. The background material of the doped glass filaments is germanium-doped silica, with a relative refractive index difference Δ3 of 0.08%, an outer diameter of 2 mm, and a duty ratio f of the fluorine-doped core region of 0.0875. . The inner casing is germanium-doped silica with a relative refractive index of Δ4=Δ3=0.08%, an inner diameter of 22 mm and an outer diameter of 45 mm. The capillaries of the outer covering layer are undoped silica glass, have an inner diameter of 4 mm and an outer diameter of 5 mm, and the 30 capillaries are densely arranged around the inner casing to form an air covering layer. The outer casing is undoped silica glass and has an inner diameter of 55 mm and an outer diameter of 100 mm.

The optical fiber preform is manufactured as follows.
(1) Fabrication of fluorinated glass filament: using PCVD process to deposit a germanium doped coating layer and a fluorinated core in a pure silicon liner; Corrode and then draw the glass rod into a specific size glass filament. Here, the Ge doping molarity of the germanium-doped coating layer is 0.8% to 1%, and the F doping molarity of the fluorine-doped core is 0.4% to 2.5%.
(2) Fabrication of ytterbium-doped glass filaments: Using MCVD-based CDS (rare earth chelate chemical vapor deposition) process to deposit ytterbium-doped cores in a pure silicon liner, and after the deposition is completed, the outer layer of the solid rod is Pure silicon is completely removed by polishing and etching processes. Here, the Yb addition molar concentration of the ytterbium-doped core is 0.15% to 0.2%.
(3) Inner casing manufacturing: PCVD technology is used to deposit a germanium-doped coating layer with a certain thickness in the pure silicon liner, and after the deposition is completed, the pure silicon of the outer layer of the casing is completely removed by polishing and corrosion processes. and extend one end of the casing into a conical shape.
(4) Capillary tube production: The pure silica casing is stretched into a capillary tube with a constant outer diameter in equal proportions, and the two ends of the capillary tube are sealed with a flame.
(5) Production of outer casing: A single pure silica casing is prepared, one end of which is extended into a conical shape, washed and dried.
(5) Assembling the preform: After washing and drying the 91 fluorine-doped glass filaments, they are stacked in a regular hexagon in a hexagonal casing. Replace with glass filaments, then bundle and fix the glass filament bundle with nickel wire and gauze, remove the hexagonal casing mold, put the glass filament bundle into the inner casing, and then replace the inner casing with the Put in outer casing. A gap between the inner casing and the outer casing is filled with the capillary tube.

The preform shown in FIG. 1 is placed in a drawing furnace and drawn to produce an all-solid-state photonic crystal fiber with an outer diameter of 800 μm.

The resulting ytterbium photonic crystal fiber, whose cross-section is shown in FIG. 25. Here, the diameter of the core is 50 μm, the diameter of the inner coating layer is 360 μm, the diameter of the outer coating layer is 800 μm, the core NA is 0.06, and the fluorine-added region of the coating layer is The diameter is 1.4 μm, the center-to-center distance between two adjacent fluorinated units is 16 μm, the radial width of the air holes is 10 μm, and the wall thickness between two adjacent air holes is , 0.5 μm, the NA of the air cladding layer is 0.85, the mode field diameter at 1064 nm of the optical fiber is 61 μm, and the single-mode operating range is greater than 820 μm as shown in FIG.

A semiconductor laser with a central wavelength of 915 nm is used as an excitation source, and the all-solid-state ytterbium-doped photonic crystal fiber according to the present invention is used as a gain medium to construct a test platform. As shown in FIG. , the cladding absorption coefficient of the optical fiber at 915 nm is measured to be 3.2 dB/m.

Using a 1064 nm single-mode laser as the signal light source, the beam quality of the all-solid double-layered ytterbium-doped photonic crystal fiber according to the present invention is measured, and its beam quality factor ^M2 is 1.1, and the output spot and M The fitted hyperbolas of ^{the two} tests are shown in FIG.

(Example 2)
The photonic crystal fiber preform includes a core 1, an inner coating fluorinated glass filament 2, an inner casing 3, an outer coating capillary 4, and an outer casing 5, as shown in FIG. Here, the core is formed by stacking seven ytterbium-doped glass filaments in a regular hexagon, and has a relative refractive index difference of Δ1=0.085% and an outer diameter of 2 mm. The inner coating layer is composed of four layers in which 84 fluorine-doped glass filaments are deposited in a regular hexagon. The background material of the doped glass filaments is germanium-doped silica, with a relative refractive index difference Δ3 of 0.08%, an outer diameter of 2 mm, and a duty ratio f of the fluorine-doped core region of 0.0875. . The inner casing is germanium-doped silica with a relative refractive index of Δ4=Δ3=0.08%, an inner diameter of 22 mm and an outer diameter of 45 mm. The background material of the outer coating layer is low refractive index glass, whose inner diameter is 45 mm and whose outer diameter is 100 mm.

The optical fiber preform is manufactured as follows.
(1) Fabrication of fluorinated glass filament: using PCVD process to deposit a germanium doped coating layer and a fluorinated core in a pure silicon liner; Corrode and then draw the glass rod into a specific size glass filament. Here, the Ge doping molarity of the germanium-doped coating layer is 0.8% to 1%, and the F doping molarity of the fluorine-doped core is 0.4% to 2.5%.
(2) Fabrication of ytterbium-doped glass filaments: Using MCVD-based CDS (rare earth chelate chemical vapor deposition) process to deposit ytterbium-doped cores in a pure silicon liner, and after the deposition is completed, the outer layer of the solid rod is Pure silicon is completely removed by polishing and etching processes. Here, the Yb addition molar concentration of the ytterbium-doped core is 0.15% to 0.2%.
(3) Inner casing manufacturing: PCVD technology is used to deposit a germanium-doped coating layer with a certain thickness in the pure silicon liner, and after the deposition is completed, the pure silicon of the outer layer of the casing is completely removed by polishing and corrosion processes. and extend one end of the casing into a conical shape.
(4) Outer Casing Fabrication: Prepare a piece of pure silicon casing, use PCVD process to deposit a low refractive index layer with a certain thickness in the pure silicon liner, after the deposition is completed, polish and An erosion process completely removes the pure silicon of the outer layer of the casing, tempering and polishing, and conicalizing one end of said casing.
(5) Assembling the preform: After washing and drying the 169 fluorine-doped glass filaments, they are stacked in a regular hexagon in a hexagonal casing. Replace with glass filaments, then bundle and fix the glass filament bundle with nickel wire and gauze, remove the hexagonal casing mold, put the glass filament bundle into the inner casing, and then replace the inner casing with the Put in outer casing.

The preform shown in FIG. 1 is placed in a drawing furnace and drawn to produce an all-solid-state photonic crystal fiber with an outer diameter of 1000 μm.

The resulting ytterbium photonic crystal fiber, whose cross-section is shown in FIG. 25. Here, the diameter of the core is 60 μm, the diameter of the inner coating layer is 450 μm, the diameter of the outer coating layer is 1000 μm, the core NA is 0.06, and the fluorine-added region of the coating layer is The diameter is 1.75 μm, the center-to-center distance between two adjacent fluorine-doped units is 20 μm, the NA of the outer coating layer is 0.23, and the mode field diameter at 1064 nm of the optical fiber is 54 μm. and the single-mode operating range is greater than 1050 μm as shown in FIG.

A semiconductor laser with a central wavelength of 915 nm is used as an excitation source, and the all-solid-state ytterbium-doped photonic crystal fiber according to the present invention is used as a gain medium to construct a test platform. As shown in FIG. , the cladding absorption coefficient of the optical fiber at 915 nm is measured to be 3 dB/m.

Using a 1064 nm single-mode laser as the signal light source, the beam quality of the all-solid-state double-layered ytterbium-doped photonic crystal fiber according to the present invention is measured, and its beam quality factor ^M2 is 1.2, and the output spot and M The fitted hyperbolas of ^{the two} tests are shown in FIG. The above description is merely a preferred embodiment of the present invention, and is not intended to limit the present invention. It is obvious to a person skilled in the art that it should be included in the scope of protection.

(Appendix)
(Appendix 1)
A photonic crystal fiber preform comprising a glass filament for forming a core, a glass filament for forming a fluoridated unit of an inner cladding layer, a glass casing for an inner cladding layer, and a glass for an outer cladding layer. a casing; and
The glass filament for forming the core has a relative refractive index difference Δ1 of 0.08% to 0.09% and a diameter of 1 to 4 mm,
The glass filament for forming the fluorine-doped unit of the inner coating layer has the same outer diameter as the glass filament for forming the core, and the coating layer and the relative refractive index difference Δ2 are -0.14% to - a core layer of 0.82%, said coating layer being the same material as the casing material of said inner coating layer, f = _dF / _d1 , where _dF is the inner coating represents the coating layer inner diameter of the glass filaments for forming the fluoridated units of the layer, and _d1 represents the coating layer outer diameter of the glass filaments for forming the fluoridated units of the inner coating layer). The duty ratio f of the fluorine addition unit is 0.085 to 0.09,
The glass casing of the inner coating layer has a thickness of 2 mm to 20 mm and a relative refractive index difference Δ3 of 0.08% to 0.1%,
The glass casing of the outer coating layer has a thickness of 30 mm to 90 mm and is a pure silica glass tube,
The glass casing of the inner cladding layer and the glass casing of the outer cladding layer are concentric nested structures, the glass filament for forming the core is in the center of the glass casing of the inner cladding layer, and the glass casing of the inner cladding layer is positioned between the glass filaments for forming the core and the inner coating layer casing;
A photonic crystal fiber preform characterized by:

(Appendix 2)
The glass casing of the inner coating layer has an inner diameter of 22 to 37.5 mm and an outer diameter of 45 to 50 mm. Between, _{1 in} D = 2n ₁ * d ₁ , n _≥ 4 and 1 mm ≤ d ₁ ≤ 4 mm (where _{1 in} D indicates the inner diameter of the glass casing of the inner coating layer, and n ₁ is the represents the number of glass filament layers of the fluorine-doped unit of the inner coating layer, and _d1 represents the outer diameter of the glass filament for forming the fluorine-doped unit of the inner coating layer).
The glass casing of the outer coating layer has an inner diameter of 50 to 60 mm and an outer diameter of 80 to 150 mm.
A photonic crystal fiber preform according to appendix 1, characterized in that:

(Appendix 3)
The glass filaments of the fluoridation unit are densely arranged in an array around a core glass filament positioned at the center of the array, and the glass filaments for forming the core and the glass filaments for forming the fluoridation unit are arranged. is 0.5 to 3:12, preferably 1:12, 7:120, 7:162, 19:84, 19:120 or 19:162,
A photonic crystal fiber preform according to appendix 1, characterized in that:

(Appendix 4)
The inner wall of the glass casing of the outer coating layer has a low refractive index layer, the low refractive index layer is a densely arranged capillary glass tube or a low refractive index glass material layer, and the capillary glass tube is , an inner diameter of 2 to 4 μm, an outer diameter of 2.5 to 5 mm, both ends of which are sealed, and the low refractive index layer has a refractive index or equivalent refractive index of 1.22 to 1.25;
A photonic crystal fiber preform according to appendix 1, characterized in that:

(Appendix 5)
including the following steps,
(1) Glass filaments for forming a fluorine-added unit and glass filaments for forming a core are stacked in a predetermined number in a regular hexagonal shape using a mold and bundled into a glass filament bundle to form the core. centering the glass filament of
(2) making the glass filament bundle obtained in step (1) into a concentric nest structure with an inner casing and an outer casing;
Preferably, the glass filament for forming the core has a rare earth-doped core layer deposited in the liner so that the relative refractive index difference Δ1 of the core layer is 0.08% to 0.1%, and the liner is Manufactured by removing and drawing,
The glass filament for forming the fluorine-doped unit deposits the inner coating layer material in the liner to a preset thickness, and then the relative refractive index difference Δ2 of the fluorine-doped glass layer is from −0.14% to Manufactured by depositing a fluorine-added glass layer to be -0.82%, removing the liner and drawing,
A method for manufacturing a photonic crystal fiber preform according to any one of Appendices 1 to 4, characterized by:

(Appendix 6)
When the inner wall of the glass casing of the outer coating layer has closely arranged capillary glass tubes,
The capillary glass tube is manufactured by drawing a pure silicon casing into a capillary tube with a predetermined outer diameter in equal proportions and sealing both ends of the capillary tube with a flame,
When the inner wall of the glass casing of the outer coating layer has a low refractive index glass material layer,
the outer coating layer is fabricated by depositing a fluorine-doped layer within a pure silica liner;
A method for manufacturing a photonic crystal fiber preform according to appendix 5, characterized by:

(Appendix 7)
A photonic crystal fiber comprising a core, an inner cladding layer, and an outer cladding layer;
The core has a relative refractive index difference Δ1 of 0.08% to 0.1% and a diameter of 40 to 50 μm,
The inner coating layer includes a background layer having a diameter of 200 to 400 μm and a relative refractive index difference Δ3 of 0.08% to 0.1%, and an array of and a fluorine-doped unit having a relative refractive index difference Δ2 of −0.14% to −0.82%,
the outer coating layer has a diameter of 800 μm to 1000 μm,
A photonic crystal fiber characterized by:

(Appendix 8)
The array-shaped fluorine-added units are distributed in a region of the inner coating layer in which the thickness to the core is 1/5 to 1/2 of the thickness of the inner coating layer,
The fluorine-added unit has a diameter of 1 to 1.4 μm,
The center-to-center distance of the fluorine-doped units is 11.5 to 16 μm.
The photonic crystal fiber according to appendix 7, characterized in that:

(Appendix 9)
the core is a silica layer co-doped with ytterbium, aluminum and phosphorus;
The outer coating layer includes a pure silica layer and a low refractive index layer, wherein the low refractive index layer is located on the innermost surface of the outer coating layer and has a refractive index or equivalent refractive index of 1.22 to 1.25. is composed of air holes or low refractive index glass material layers arranged in the circumferential direction,
The photonic crystal fiber according to appendix 7, characterized in that:

(Appendix 10)
acting as a gain medium,
Use of a photonic crystal fiber according to any one of appendices 7 to 9, characterized in that:

Identical elements or structures are provided with identical reference numerals in all figures.
1: glass filament for forming the core of the photonic crystal fiber preform, 2: glass filament for forming the fluorine-doped unit of the inner coating layer, 3: glass casing of the inner coating layer, 4: capillary glass Tube, 5: glass casing of outer coating layer, 21: core of optical fiber, 22: fluorinated unit, 23: background material, 24: air holes of outer coating layer, 25: outer coating layer.

Claims (12)

A photonic crystal fiber preform comprising a glass filament for forming a core, a glass filament for forming a fluoridated unit of an inner cladding layer, a glass casing for an inner cladding layer, and a glass for an outer cladding layer. a casing; and
The glass filament for forming the core has a relative refractive index difference Δ1 of 0.08% to 0.09% and a diameter of 1 to 4 mm,
The glass filament for forming the fluorine-doped unit of the inner coating layer has the same outer diameter as the glass filament for forming the core, and the relative refractive index difference Δ2 between the coating layer and the coating layer is -0.14% or more. -0.82%, said coating layer being the same material as the material of the glass casing of said inner coating layer, f=d _F /d ₁ , where d _F is represents the coating layer inner diameter of the glass filaments for forming the fluorine-added units of the inner coating layer, and _d1 represents the coating layer outer diameter of the glass filaments for forming the fluorine-added units of the inner coating layer). The calculated duty ratio f of the fluorine addition unit is 0.085 to 0.09,
The glass casing of the inner coating layer has a thickness of 2 mm to 20 mm and a relative refractive index difference Δ3 of 0.08% to 0.1%,
The glass casing of the outer coating layer has a thickness of 30 mm to 90 mm and is a pure silica glass tube,
The glass casing of the inner cladding layer and the glass casing of the outer cladding layer are concentric nested structures, and the glass filament for forming the core is in the center of the glass casing of the inner cladding layer and the inner the glass filaments for forming the fluorinated units of the coating layer are located between the glass filaments for forming the core and the glass casing of the inner coating layer;
A photonic crystal fiber preform characterized by: The glass casing of the inner coating layer has an inner diameter of 22 to 37.5 mm and an outer diameter of 45 to 50 mm. and the number of layers, _{1 in} D = 2n ₁ * d ₁ , n _≥ 4 and 1 mm ≤ d ₁ ≤ 4 mm (where ₁ in D indicates the inner diameter of the glass casing of the inner coating layer, _n1 indicates the number of glass filament layers for forming the fluorine-added unit of the inner coating layer, and _d1 indicates the outer diameter of the glass filament for forming the fluorine-added unit of the inner coating layer) have a relationship of
The glass casing of the outer coating layer has an inner diameter of 50 to 60 mm and an outer diameter of 80 to 150 mm.
The photonic crystal fiber preform according to claim 1, characterized in that: The glass filaments for forming the fluorine-added units of the inner coating layer are densely arranged in an array around a core glass filament positioned at the center of the array, and the glass filaments for forming the core and the inner coating layer and the number ratio of the glass filaments for forming the fluorine doping unit is 0.5 to 3:12.
The photonic crystal fiber preform according to claim 1, characterized in that: The number ratios of the glass filaments for forming the core and the glass filaments for forming the fluorinated units of the inner coating layer are 1:12, 7:120, 7:162, 19:84, 19: 120, or 19:162;
The photonic crystal fiber preform according to claim 3, characterized in that: The inner wall of the glass casing of the outer coating layer has a low refractive index layer, the low refractive index layer is a densely arranged capillary glass tube or a low refractive index glass material layer, and the capillary glass tube is , an inner diameter of 2 to 4 μm, an outer diameter of 2.5 to 5 mm, both ends of which are sealed, and the low refractive index layer has a refractive index or equivalent refractive index of 1.22 to 1.25;
The photonic crystal fiber preform according to claim 1, characterized in that: including the following steps,
(1) A predetermined number of glass filaments for forming the fluorine-added units of the inner coating layer and glass filaments for forming the core are stacked in a regular hexagonal shape using a mold and bundled into a glass filament bundle, centering a glass filament to form the core;
(2) forming the glass filament bundle obtained in step (1) into a concentric nest structure of an inner casing and an outer casing ;
A method for manufacturing a photonic crystal fiber preform according to any one of claims 1 to 5 , characterized in that: The glass filament for forming the core is obtained by depositing a rare earth-doped core layer in the liner and removing the liner so that the relative refractive index difference Δ1 of the core layer is 0.08% to 0.1%. manufactured by drawing
7. The method of manufacturing a photonic crystal fiber preform according to claim 6, wherein: The glass filament for forming the fluorine-doped unit of the inner coating layer deposits the inner coating layer material in the liner to a preset thickness, and then the relative refractive index difference Δ2 of the fluorine-doped glass layer is -0. .14% to -0.82% of the fluorine-added glass layer is deposited, the liner is removed, and the wire is drawn.
7. The method of manufacturing a photonic crystal fiber preform according to claim 6, wherein: the inner wall of the glass casing of the outer covering layer has closely aligned capillary glass tubes;
The capillary glass tube is manufactured by drawing a pure silica casing into a capillary tube with a predetermined outer diameter at an equal ratio, and sealing both ends of the capillary tube with a flame.
or
the inner wall of the glass casing of the outer coating layer having a low refractive index glass material layer;
the outer coating layer is fabricated by depositing a fluorine-doped layer within a pure silica liner;
7. The method of manufacturing a photonic crystal fiber preform according to claim 6 , wherein: A photonic crystal fiber comprising a core, an inner cladding layer, and an outer cladding layer;
The core has a relative refractive index difference Δ1 of 0.08% to 0.1% and a diameter of 40 to 50 μm,
The inner coating layer includes a background layer having a diameter of 200 to 400 μm and a relative refractive index difference Δ3 of 0.08% to 0.1%, and a fluorine-doped units arranged in an array and having a relative refractive index difference Δ2 of −0.14% to −0.82%;
the outer coating layer has a diameter of 800 μm to 1000 μm,
A photonic crystal fiber characterized by: The array-shaped fluorine-added units are distributed in a region of the inner coating layer in which the thickness to the core is 1/5 to 1/2 of the thickness of the inner coating layer,
The fluorine-added unit has a diameter of 1 to 1.4 μm,
The center-to-center distance of the fluorine-doped units is 11.5 to 16 μm.
11. The photonic crystal fiber of claim 10 , wherein: the core is a silica layer co-doped with ytterbium, aluminum and phosphorus;
The outer coating layer includes a pure silica layer and a low refractive index layer, and the low refractive index layer is located on the innermost surface of the outer coating layer and has a refractive index or an equivalent refractive index of 1.22 to 1.22. 25, composed of circumferentially arranged air holes or layers of low refractive index glass material,
11. The photonic crystal fiber of claim 10 , wherein:

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