Single-mode optical fiber with large fiber core diameter

Abstract

The invention provides a single-mode optical fiber with a large fiber core diameter. The single-mode optical fiber is mainly characterized by comprising a fiber core, an inner cladding and an outer cladding, wherein the fiber core is used for absorbing pump light and converting the pump light into signal light, the fiber core is doped with rare earth elements and other co-doped elements, and a refractive index of the fiber core is lower than that of the material of the inner cladding; the inner wrapping layer wraps the fiber core, the main material of the inner wrapping layer is pure quartz glass or other doped quartz glass, and two kinds of air holes are distributed in the inner wrapping layer; and the outer cladding layer wraps the inner cladding layer, and the outer cladding layer is composed of a circle of air holes which surround the inner cladding layer and are tightly arranged.

Description

technical field [0001] The invention relates to the field of optical fiber technology, in particular to a type of active single-mode photonic crystal optical fiber with a large core diameter, which is mainly used in 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 fiber has many advantages, such as large specific surface area of ​​optical fiber, so cooling requirements are low, the single-mode output of optical fiber is similar to Gaussian beam, so the beam quality is good, the optical fiber is mainly made of quartz glass, so the production is efficient and the cost is relatively low, and almost all optical systems are in the Internal transmission of optical fiber, so it is more stable, reliable and maintenance-free. In summary, fiber lasers have be...

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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