Step-Gaussian composite type doped ion concentration distribution gain fiber

Abstract

The invention provides a gain fiber with step and gauss composite ion doping concentration distribution, and belongs to the technical field of fiber lasers. In gain light output, fundamental mode optical power ratio is not high in the prior art. The gain fiber with step and gauss composite ion doping concentration distribution is a large-core-diameter multimode fiber and is of a double-cladding structure, and rare earth ions are doped in a fiber core doping radius R'1. The gain fiber is characterized in that distribution of ion doping concentration N is divided into two areas, a round 0-R0 area in the range of a fiber core radius R1 is a step area, R0 is the radius of the step area, and R0 is less than R'1, in the step area, distribution of the ion doping concentration N is a step type, and the ion doping concentration N is the maximum value Nmax; an annular R0-R'1 area in the fiber core radius R1 is a gauss area, in the gauss area, distribution of the ion doping concentration N is a gauss type, the ion doping concentration N is determined by the following formula (please see the formula in the instruction), and in the formula, r is the radius of the gain fiber.

Description

technical field [0001] The invention relates to a step-Gauss compound type doping ion concentration distribution gain fiber, which belongs to the technical field of fiber laser. Background technique [0002] Gain fibers are used as wavelength converters, optical amplifiers, fiber lasers, etc., and have a double-clad structure. The fibers are core 1, inner cladding 2, outer cladding 3, and protective layer 4 in sequence from the inside to the outside, such as figure 1 As shown, the core 1 and the outer cladding 3 are circular, and the radius of the core 1 is the core radius R 1 , the inner cladding 2 generally adopts a special-shaped structure, and its cross-sectional shapes include oval, rectangular, quincunx, D-shaped, and hexagonal, etc., and rectangles are commonly used, such as squares. At this time, the inner cladding 2 has a radius R 2 Refers to the radius of the inscribed circle of a square, and the rectangular inner cladding 2 can increase the laser conversion effic...

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Problems solved by technology

However, at the dopant ion concentration maximum N max Under the same premise, the fundamental mode gain in the central region of the mode field is also reduced compared with the step type

Moreover, the unilateral parabola has no inflection point and is a complete convex curve. The dopant ion concentration N does not decrease rapidly as the fiber radius r increases from the center O, and the suppression effect on the high-order mode gain is not optimal.

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