A single-mode fiber with a large core diameter

Abstract

The invention provides a type of single-mode optical fiber with a large core diameter. Doping rare earth elements and other co-doping elements, the refractive index of which is lower than the refractive index of the inner cladding material; the inner cladding layer covers the core, and the main material of the inner cladding layer is pure silica glass or other doped silica glass , and two kinds of air holes are distributed therein; the outer cladding covers the inner cladding, and the outer cladding is composed of a circle of air holes closely arranged around the inner cladding.

Description

technical field [0001] The invention relates to the technical field of optical fibers, in particular to a class of active single-mode photonic crystal optical fibers with large core diameters, which are mainly applied to optical fiber lasers and optical fiber amplifiers. Background technique [0002] In recent decades, fiber lasers have gradually replaced other types of lasers and have been widely used in scientific research, medical treatment, and especially industrial manufacturing. Optical fibers have many advantages, such as the large specific surface area of ​​the optical fiber and therefore low cooling requirements, the single-mode optical fiber outputting a nearly Gaussian beam and thus good beam quality, the optical fiber is mainly made of silica glass, so the production is efficient and the cost is relatively low, in addition, almost all optical path systems are in The optical fiber is internally transmitted, so it is more stable, reliable and maintenance-free. In ...

AI Technical Summary

Problems solved by technology

Fiber lasers have become the most mainstream lasers at present. However, to achieve higher indicators, especially for ultrafast lasers, the pulse energy of tens of microjoules to millijoules puts forward stricter requirements for the single-mode effective area of ​​the fiber core. , which makes the design and manufacture of optical fibers will face some major technical difficulties. On the one hand, the single pulse energy of tens of microjoules to hundreds of microjoules of the current high-power ultrafast fiber laser is unbearable for ordinary small core diameter fibers. , but requires the core diameter of the fiber to be 25 microns, 30 microns, 40 microns, 80 microns, or even 100 microns, and to maintain high single-mode purity; on the other hand, high energy density will cause nonlinear effects, in order to avoid nonlinear effect also requires a large core diameter to reduce the energy density of the pulse

[0003] There are many design schemes for active single-mode fiber to achieve large effective mode field area, such as helical chiral coupling fiber, etc. However, the existing large-core active fiber achieves active single-mode The mode fiber mainly adopts the step-type few-mode fiber, and the quasi-single-mode is realized by bending the fiber to filter out the high-order mode. Active single-mode fibers with a micron core diameter are more difficult to realize with step-type fibers, because the extremely low core-in-pack refractive index difference has uncontrollable and difficult-to-achieve defects for conventional manufacturing processes, so photonic crystal fibers are mainly used Design, and allow the fiber to have a certain bending under appropriate circumstances; the active fiber with a core diameter of more than 40 microns can only use a rod-shaped photonic crystal fiber. Patent CN103080796B discloses a single-mode fiber with a large core area. Any fiber with this The single-mode fiber has the same large core diameter and extremely low numerical aperture NA and cannot be bent. In addition, the single-mode fiber is expensive, mainly because the production process is difficult

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