Rare earth ion annular doping double-cladding optical fiber

Abstract

The invention provides a rare earth ion annular doped double-cladding fiber, which comprises a undoped fiber core, an inner cladding, an outer cladding and an annular doped region which is positioned between the fiber core and the inner cladding; wherein, the annular doped region is a circular ring shape doped rare earth ion region surrounding the fiber core; the refractive index of the annular doped region is lower than that of the fiber core and higher than that of the inner cladding layer. On the one hand, the annular doped region increases the rare earth ion doped region, increases the probability that pump light is coupled with the rear earth doped region, and improves the efficiency of the fiber absorbing the pump light; the using length of the fiber is reduced. On the other hand, the structure can cause the laser which is generated by the annular region to be coupled with the undoped rare earth ion fiber core, the laser transmission loss caused by Yb<3+> and co-doped Al<3+> is reduced, and at the same time, the beam quality of the structure can be controlled through the undoped fiber core numerical aperture and structure.

Description

technical field [0001] The invention belongs to the technical field of special optical fibers, and relates to a double-clad optical fiber with a rare earth ion ring-doped structure. Background technique [0002] Fiber lasers originally used rare earth-doped single-mode fibers as gain media, but because the fiber core is very thin, only a few microns, the coupling efficiency with the pump source is low, and the efficiency and power of the output laser are very low, which limits scope of its use. In order to solve the limitations of fiber laser output power and efficiency, American researchers proposed the structure of double-clad fiber. Compared with ordinary fiber, double-clad fiber includes outer cladding, inner cladding and core doped with rare earth ions. The refractive index of the outer cladding is lower than that of the inner cladding, and the refractive index of the inner cladding is lower than that of the core. The inner cladding acts as a waveguide for the pump li...

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Problems solved by technology

As a result, photonic crystal fibers have emerged, but photonic crystal fibers have a complex air hole structure, and their manufacturing process is complicated, and it is difficult to control the uniformity and consistency of the structure; although increasing the size of the doped core can increase the absorption coefficient, but due to After the core size increases, the control of the numerical aperture (NA) of the fiber core is getting higher and higher. From the previous NA=0.1-0.15, it must be reduced to about 0.05, otherwise the quality of the laser output beam will be deteriorated, and this is in the optical fiber manufacturing process. difficult to realize

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