JP2014017457A5 - - Google Patents

Description

(3) The transmission path for transmission through the core is preferably a single-mode transmission path, and the core size is reduced in order to realize ultrafine processing, and the relative refractive index difference between the core and the first cladding layer is increased. doing. Therefore, many additives for increasing the refractive index are added in the core, but the difference in softening temperature between the core and the first cladding layer on the outer periphery of the core becomes large, and the coefficient of thermal expansion is increased in manufacturing the fiber. The difference comes out and it is difficult to make stable production.

In order to obtain a high-power laser beam, it is preferable that the core glass has a large diameter and that the relative refractive index difference with the cladding is not so large in order to suppress higher-order modes in the signal amplification light. Therefore, by providing a plurality of holes in the cladding made of SiO ₂ glass, the refractive index of the cladding can be reduced equivalently, and the number m of the holes, the hole diameter d, the hole interval Λ The above-mentioned equivalent refractive index can be controlled by, for example. Thus, as the addition amount of the rare earth element added to the core glass can be optimized within a range that does not cause concentration quenching, to increase the refractive index to be added to the core glass of SiO ₂ system including a rare earth element The amount of additives (eg, GeO ₂ , P ₂ O ₅ , TiO ₂ , Al ₂ O ₃ , BaO, ZrO ₂ , N, etc.) can be reduced and adjusted. As a result, the excitation efficiency of the rare earth ions by the excitation light can be optimized, and the energy conversion efficiency from the excitation light to the signal light amplification can be improved.
As another effect, the softening temperature of the core glass can be made close to the softening temperature of the clad, resulting in a difference in softening temperature when the fiber preform is heated to a high temperature state. Shape deformation can be suppressed to a small level, and manufacturing becomes easy. That is, a fiber shape similar to the shape of the fiber preform can be easily realized. In particular, it is effective for realizing a fiber structure in which a desired shape of the air gap is maintained in the fiber by bringing the softening temperature closer.

1A is a cross-sectional view of a fiber according to a first embodiment of the present invention, and FIG. A processing example (a) using a conventional fiber and a processing example (b) using the fiber of FIG . The cross-sectional view of the fiber which concerns on 2nd Example of this invention. The cross-sectional view of the fiber which concerns on 3rd Example of this invention. The cross-sectional view of the fiber which concerns on 4th Example of this invention. The cross-sectional view of the fiber which concerns on 5th Example of this invention. The cross-sectional view of the fiber which concerns on 6th Example of this invention. The cross-sectional view of the fiber which concerns on 7th Example of this invention. The transverse cross section of the fiber concerning the 8th example of the present invention. The cross-sectional view of the fiber which concerns on 9th Example of this invention. The cross-sectional view of the fiber which concerns on 10th Example of this invention. The cross-sectional view of the fiber which concerns on 11th Example of this invention. The cross-sectional view of the fiber which concerns on 12th Example of this invention. The cross-sectional view of the fiber which concerns on 13th Example of this invention. The cross-sectional view of the fiber which concerns on 14th Example of this invention. The cross-sectional view (a) of the fiber which concerns on 15th Example of this invention, The figure (b) which shows a near field pattern. The cross-sectional view of the fiber which concerns on 16th Example of this invention. The cross-sectional view of the fiber which concerns on 17th Example of this invention. The transverse cross section of the fiber concerning the 18th example of the present invention. The cross-sectional view of the fiber which concerns on 19th Example of this invention. The cross-sectional view of the fiber which concerns on 20th Example of this invention. The cross-sectional view of the fiber which concerns on 21st Example of this invention. The cross-sectional view of the fiber which concerns on 22nd Example of this invention. The cross-sectional view of the fiber which concerns on 23rd Example of this invention. The cross-sectional view of the fiber which concerns on 24th Example of this invention. The cross-sectional view of the fiber which concerns on 25th Example of this invention. A cross-sectional view of a fiber according to a twenty-sixth embodiment of the present invention. The figure for demonstrating the manufacturing method of the fiber which concerns on 27th Example of this invention. The figure for demonstrating the manufacturing method of the fiber which concerns on 28th Example of this invention. The figure for demonstrating the manufacturing method of the fiber which concerns on 28th Example of this invention. The schematic block diagram of the fiber laser which concerns on 29th Example of this invention. The schematic block diagram of the fiber type amplifier which concerns on 30th Example of this invention. The figure which shows the example of the conventional fiber. The figure which shows the example of the conventional fiber. The figure which shows the example of the conventional fiber. The figure which shows the example of the conventional fiber. The figure which shows the example of the conventional fiber. The figure which shows the example of the conventional fiber.

FIG. 5 shows a fourth embodiment of the fiber of the present invention. This fiber has a core glass 1 having a SiO ₂ -based rectangular structure containing a rare earth element at its center, and a low refractive index clad 2d made of SiO ₂ glass having a rectangular cross section on the outer periphery thereof. enclosed in SiO ₂ glass 4d with the addition of F in which the octagonal structure the outer periphery of the cladding 2d, is a fiber which is characterized in that covering the SiO ₂ glass 4d with the addition of the F in SiO ₂ glass 5d. In this fiber, the outer periphery of the low refractive index clad 2d made of SiO ₂ glass having a rectangular structure is covered with a wide space 3d, so that the NA of the transmission path for transmitting the excitation light can be increased. Note that the SiO ₂ glass 4d to which F is added covers the cladding 2d in a state where the corners of the cladding 2d are in contact with each other at four locations (6-1, 6-2, 6-3, 6-4). The outer periphery of the SiO ₂ glass 4d to which the F is added is covered with the SiO ₂ glass 5d.
In the fiber having such a structure, when the base material is drawn into a fiber, the four corners of the low refractive index clad 2d made of SiO ₂ glass having a rectangular structure are slightly rounded. This is also acceptable. is there. In addition, the eight corners of the SiO ₂ glass 4d to which F having an octagonal structure is added are slightly rounded when the fiber is drawn, but this is sufficiently acceptable because it hardly affects the fiber characteristics. is there.

When this manufacturing method is used, the low refractive index clad 2 made of SiO ₂ glass can be formed on the outer periphery of the SiO ₂ -based core glass 1 to which the rare earth element is added. Scattering loss due to non-uniformity can be reduced.
Further, solidifying the starting material of low refractive index the outermost SiO ₂ glass 5 also liquid source with the cladding 2 made of the SiO ₂ glass, to manufacture a preform at a low cost by forming together by heating Can do. In the above, the core glass 1 to which the rare earth element is added is impregnated with an aqueous solution of YbCl ₃ on a porous SiO ₂ glass rod to which GeO ₂ and Al ₂ O ₃ added by the VAD method are added, and then dried in a chlorine atmosphere. Produced by high temperature heating. Then, a glass rod 13 produced by forming a SiO ₂ glass in a thickness of 20μm on the outer circumference of the core glass 1 with the addition of the rare earth elements.

Claims (18)

The center of the fiber has a high refractive index core glass made of SiO ₂ glass containing rare earth elements, and the core glass has a low refractive index clad made of SiO ₂ glass containing no rare earth elements. Then, most of the outer periphery of the cladding is covered with voids, and the outer periphery of the voids is covered with SiO ₂ glass added with F at at least three locations on the outer periphery of the cladding, and the SiO ₂ doped with F is added. A fiber characterized in that the outer periphery of glass is covered with SiO ₂ glass not containing F. A high refractive index core glass made of SiO ₂ glass containing rare earth elements in the center of the fiber, a clad made of SiO ₂ glass not containing rare earth elements provided on the outer periphery of the core glass, and an outer periphery of the cladding And a SiO ₂ glass layer added with F,
Most of the outer periphery of the SiO ₂ glass layer to which F has been added is covered with a gap, and the SiO ₂ glass to which F has been added is in contact with the outer periphery of the gap at at least three locations on the outer periphery of the SiO ₂ glass layer to which the F has been added. a structure for covering the fiber, characterized in that the outer periphery of the SiO ₂ glass doped with the F is covered with SiO ₂ glass without addition of F. A high refractive index core glass made of SiO ₂ glass containing rare earth elements in the center of the fiber, a clad made of SiO ₂ glass not containing rare earth elements provided on the outer periphery of the core glass, and an outer periphery of the cladding And a SiO ₂ glass layer added with F,
Covered with voids most of the outer periphery of the SiO ₂ glass layer with the addition of the F, contact with SiO ₂ glass without addition of F on the outer periphery of the void in at least three places of the outer periphery of the SiO ₂ glass layer with the addition of the F A fiber characterized by having a structure to cover. The fiber according to any one of claims 1 to 3, wherein a plurality of the high refractive index core glasses made of SiO ₂ glass containing rare earth elements are arranged at a predetermined interval at the center of the fiber. A fiber characterized by The fiber according to any one of claims 1 to 4, wherein an outer cross-sectional shape of the high refractive index core glass made of SiO ₂ glass containing rare earth elements is rectangular, polygonal, or circular. Fiber. The fiber according to any one of claims 1 to 5, wherein the outer cross-sectional shape is a circle and the corner is a rounded rectangle or a polygon. The fiber according to any one of claims 1 to 6, wherein the fiber has a plurality of holes in the low refractive index clad made of SiO ₂ glass. 8. The fiber according to claim 7, wherein the holes in the cladding having a low refractive index made of SiO ₂ glass containing the plurality of holes are arranged in a triangular lattice shape at a predetermined interval. A fiber characterized by forming a structure. The fiber according to any one of claims 1 to 8, wherein the rare earth element contained in the core glass is at least one of Er, Yb, Nd, Eu, Pr, Tm, Ho, La, Sm, and Ce. A fiber characterized by containing. The fiber according to any one of claims 1 to 9, wherein the core glass is SiO ₂ glass, GeO ₂ , P ₂ O ₅ , TiO ₂ , Al ₂ O ₃ , BaO, B ₂ O ₃ , ZrO ₂ , A fiber characterized by being SiO ₂ glass containing at least one of F and N. The fiber according to any one of claims 1 to 10, wherein an outer cross-sectional shape of the cladding is any one of a circle, a triangle, a rectangle, a hexagon, or a triangle, a rectangle, and a hexagon with rounded corners. Characteristic fiber. 3. The fiber according to claim 1 , wherein when the outer cross-sectional shape of the cladding is circular, the cross-sectional shape of the hollow portion of the SiO ₂ glass to which F is added is a rectangle, a triangle, or a polygon. Characteristic fiber. 3. The fiber according to claim 1 , wherein when the outer cross-sectional shape of the clad is a triangle or a quadrangle, the cross-sectional shape of the hollow portion of the SiO ₂ glass to which the F is added is a circle or a polygon. And fiber. 3. The fiber according to claim 1 , wherein when the outer cross-sectional shape of the clad is a polygon, the cross-sectional shape of the hollow portion of the SiO ₂ glass to which the F is added is circular. In the fiber according to any one of claims 1 to 14, the cladding and the outermost periphery of the SiO ₂ glass having a low refractive index of SiO ₂ based glass, the starting materials of SiO ₂ liquid material solidifies, heat A fiber characterized by being formed. The fiber according to any one of claims 1 to 14, wherein a liquid raw material of SiO ₂ is filled in a mold and solidified, then the solidified body is detached from the mold, and the solidified body is heated at high temperature in a chlorine atmosphere. A fiber obtained by drawing a fiber preform obtained by vitrification at a high temperature. The fiber type amplifier comprising the fiber according to any one of claims 1 to 16, wherein signal light is coupled into the core glass of the fiber, and excitation light for exciting the rare earth element is made of SiO ₂ glass containing the core glass. A fiber-type amplifier characterized by being coupled and propagated in a low refractive index clad.   The fiber according to any one of claims 1 to 16, and a wavelength-selective total reflection mirror that totally reflects laser light and transmits excitation light is disposed on an input end side of the fiber, and an output end side of the fiber Is provided with a reflecting mirror that semi-transmits the laser light so that the excitation light is coupled and propagated from the input end side of the fiber into the cladding, and the laser light is emitted from the output end side of the fiber. A fiber laser characterized by that.

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