CN-121978795-A - Chiral coupling ytterbium-doped optical fiber and high-power optical fiber laser

CN121978795ACN 121978795 ACN121978795 ACN 121978795ACN-121978795-A

Abstract

The invention provides a chiral coupling ytterbium-doped optical fiber and a high-power optical fiber laser, and relates to the technical field of optical fibers. The ytterbium-doped optical fiber sequentially comprises a central fiber core, a plurality of spiral side cores, an inner cladding and an outer cladding from inside to outside, wherein the plurality of spiral side cores are spirally wound on the central fiber core along the axial direction of the central fiber core, the refractive index of a fundamental mode of at least one spiral side core in the plurality of spiral side cores is different from the refractive index of the central fiber core in a preset high-order mode, and the thermo-optical coefficient of the spiral side core which is different from the refractive index of the central fiber core in the preset high-order mode is larger than that of the central fiber core. The chiral coupling ytterbium-doped fiber provided by the invention can effectively remove the high-order mode in the central fiber core.

Inventors

GENG PENGCHENG
YI YONGQING
SHEN YIZE
WANG SUYU
PAN RONG
HAN ZHIHUI
ZHANG HUIJIA

Assignees

中国电子科技集团公司第四十六研究所

Dates

Publication Date: 20260505
Application Date: 20260106

Claims (10)

1. The chiral coupling ytterbium-doped optical fiber is characterized by comprising a central fiber core and a plurality of spiral side cores from inside to outside in sequence, wherein the plurality of spiral side cores are spirally wound on the central fiber core along the axial direction of the central fiber core; the refractive index of the fundamental mode of at least one spiral side core in the plurality of spiral side cores is different from the refractive index of the central fiber core in a preset high-order mode, and the thermo-optical coefficient of the spiral side core which is different from the refractive index of the central fiber core in the preset high-order mode is larger than that of the central fiber core.
2. The chiral coupling ytterbium doped fiber of claim 1, wherein the fundamental mode refractive indices of all of the spiral side cores comprise at least 3 different values, and wherein the thermo-optic coefficients of all of the spiral side cores are greater than the thermo-optic coefficients of the central core.
3. The chiral-coupled ytterbium-doped optical fiber of claim 2, wherein the predetermined higher-order mode is an LP11 mode, wherein all of the spiral side cores comprise 3 groups, wherein a fundamental mode refractive index of a first group of the spiral side cores is the same as a refractive index of the central core in the LP11 mode at room temperature, a fundamental mode refractive index of a second group of the spiral side cores is the same as a refractive index of the central core in the LP21 mode at room temperature, a fundamental mode refractive index of a third group of the spiral side cores is the same as a refractive index of the central core in the LP02 mode at room temperature, and wherein at least one spiral side core is included in each of the first, second, and third groups of the spiral side cores.
4. The chiral coupling ytterbium doped fiber of claim 3, wherein the thermo-optic coefficients of all of the spiral side cores in the first set of spiral side cores are the same, the thermo-optic coefficients of all of the spiral side cores in the second set of spiral side cores are the same, and the thermo-optic coefficients of all of the spiral side cores in the third set of spiral side cores are the same.
5. The chiral coupling ytterbium doped fiber of claim 4, wherein the thermo-optic coefficients of the first set of spiral side cores, the second set of spiral side cores, and the third set of spiral side cores are all different.
6. The chiral-coupled ytterbium-doped fiber of claim 3, wherein the first set of spiral side cores includes 3 spiral side cores, the second set of spiral side cores includes 2 spiral side cores, the third set of spiral side cores includes 3 spiral side cores, and the 2 spiral side cores in the second set of spiral side cores are symmetrically disposed on either side of the central core, and the first set of spiral side cores and the third set of spiral side cores are symmetrically disposed on either side of the central core.
7. The chiral-coupled ytterbium-doped fiber of claim 3, wherein the first set of spiral side cores includes 2 spiral side cores therein, the second set of spiral side cores includes 4 spiral side cores therein, the third set of spiral side cores includes 2 spiral side cores therein, and the 4 spiral side cores in the second set of spiral side cores are symmetrically disposed on either side of the central core, the first set of spiral side cores and the third set of spiral side cores are symmetrically disposed on either side of the central core.
8. The chiral coupling ytterbium-doped fiber of any of claims 1-7, wherein the ytterbium-doped fiber is single tapered, the central core having a diameter greater than 25 microns.
9. The chiral coupling ytterbium-doped fiber of any of claims 1-7, further comprising an inner cladding, the inner cladding having a shape that is circular, D-shaped, or polygonal.
10. A high power fiber laser, comprising the chiral coupling ytterbium-doped fiber of any of claims 1-9.

Description

Chiral coupling ytterbium-doped optical fiber and high-power optical fiber laser Technical Field The invention relates to the technical field of optical fibers, in particular to a chiral coupling ytterbium-doped optical fiber and a high-power optical fiber laser. Background The fiber laser using ytterbium-doped fiber as gain medium has the advantages of high full-electric driving and electro-optical conversion efficiency, flexible transmission and the like, and is widely applied to high-end laser processing industries such as laser drilling, laser cutting, laser welding, laser cleaning, laser quenching and the like, and the fields such as laser medical treatment, laser interception and the like. The high-power fiber laser is limited by the mode instability (TRANSVERSE MODE INSTABILITY, TMI) effect, so that the laser beam light spot output by the high-power fiber laser is large and unstable, and the processing precision and the service life of a laser processing system are seriously affected. As shown in fig. 1, after the laser output power exceeds a certain threshold, the output mode of the ytterbium-doped fiber may change randomly, such as the conversion between the fundamental mode and the higher-order mode, so that the light spot degradation and the rapid increase of the laser output power are caused. To achieve high power output, the high power fiber laser must have a larger central core diameter to suppress nonlinear effects and thermal damage caused by the high power laser. However, a plurality of transmission modes exist in the ytterbium-doped fiber core with a larger central fiber core diameter, so that single-mode output cannot be realized, and the transmission requirement of a high-power fiber laser cannot be met. Furthermore, the inventors have found that high power fiber lasers have output powers as high as thousands of watts and tens of thousands of watts, also resulting in the inability to remove higher order modes in the central core. Disclosure of Invention The embodiment of the invention provides a chiral coupling ytterbium-doped optical fiber and a high-power optical fiber laser, which are used for solving the problem that the existing large-core-diameter ytterbium-doped optical fiber cannot effectively inhibit the generation of a high-order mode in a central fiber core. In a first aspect, an embodiment of the present invention provides a chiral coupling ytterbium-doped optical fiber, where the ytterbium-doped optical fiber sequentially includes a central core and a plurality of spiral side cores from inside to outside, where the plurality of spiral side cores are spirally wound on the central core along an axial direction of the central core; The refractive index of the fundamental mode of at least one spiral side core in the spiral side cores is different from that of the central fiber core in a preset high-order mode, and the thermo-optic coefficient of the spiral side core which is different from that of the central fiber core in the preset high-order mode is larger than that of the central fiber core. In one possible implementation, the fundamental mode refractive indices of all the spiral side cores include at least 3 different values, and the thermo-optic coefficients of all the spiral side cores are greater than the thermo-optic coefficient of the central core. In one possible implementation manner, the preset high-order mode is an LP11 mode, all the spiral side cores comprise 3 groups, the basic mode refractive index of the first group of spiral side cores is the same as the refractive index of the central fiber core in the LP11 mode at room temperature, the basic mode refractive index of the second group of spiral side cores is the same as the refractive index of the central fiber core in the LP21 mode at room temperature, the basic mode refractive index of the third group of spiral side cores is the same as the refractive index of the central fiber core in the LP02 mode at room temperature, and at least one spiral side core is arranged in each of the first group of spiral side cores, the second group of spiral side cores and the third group of spiral side cores. In one possible implementation, the thermo-optic coefficients of all the spiral side cores in the first set of spiral side cores are the same, the thermo-optic coefficients of all the spiral side cores in the second set of spiral side cores are the same, and the thermo-optic coefficients of all the spiral side cores in the third set of spiral side cores are the same. In one possible implementation, the thermo-optic coefficients of the first set of spiral side cores, the second set of spiral side cores, and the third set of spiral side cores are all different. In one possible implementation manner, the first set of spiral side cores includes 3 spiral side cores, the second set of spiral side cores includes 2 spiral side cores, the third set of spiral side cores includes 3 spiral side cores, and the 2 spiral side cores in