A region coated end cap group for suppressing mode instability and application thereof

Abstract

A region coated end cap group for suppressing mode instability comprises a first end cap and a second end cap, the two end caps comprising an optical fiber and a quartz block; The quartz block is formed by connecting a circular table, and the cylinder and the output curved surface in turn to form an integral structure, wherein the circular table, the cylinder and the output curved surface has thesame connecting end face. One end face of the optical fiber is welded with the smaller end face of the circular table to form an interface; The extension line of the core line of the optical fiber isthe center line of the circular table, the cylinder and the output curved surface; The surface of the output curved surface is centered on the intersection point of the core extension line and the interface of the optical fiber, Taking the sum of the lengths of the quartz block centerline in the circular table, the cylinder and the output curved surface as the radius of curvature, the different regions of the output curved surface have different coatings, the space region of the fundamental mode on the first end cap curved surface is a high reflectivity film, and the region outside the fundamental mode is a full transmission film; The space region of the fundamental mode on the curved surface of the second end cap is a low-reflectivity film, and the region other than the fundamental mode is a full-transmission film. The invention can suppress the mode instability effect in the all-optical fiber oscillator.

Description

technical field [0001] The invention generally relates to the field of fiber lasers, in particular to an end cap group for suppressing mode instability and its application. Background technique [0002] High-power fiber lasers are widely used in laser cutting, laser cladding, 3D printing and other fields. In recent years, with the double-clad fiber manufacturing process and the power increase of high-brightness semiconductor lasers, the output power of single-channel high-power fiber laser has been developed rapidly, from 100 watts at the beginning of the 21st century to the current 10 kilowatts. With the continuous improvement of fiber laser output power, the mode instability effect has become the main factor limiting the increase of high-power fiber laser output power. The way to suppress mode instability in traditional fiber lasers is to increase the bending loss of the gain fiber and select the wavelength of the pump source corresponding to the low absorption coefficien...

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Problems solved by technology

[0005] For the above-mentioned existing technologies, the mode instability effect is suppressed by using a gain fiber that supports few fiber modes, using a pump source corresponding to a low absorption coefficient of the gain fiber, and increasing the bending loss of the fiber to reduce the mode instability effect. The oscillation of high-order modes cannot be substantially reduced. With the increase of output power, the mode instability effect will still appear. At the same time, the fundamental mode oscillation is effectively improved, and a large amount of high-order modes are lost, thereby suppressing the mode instability effect of the fiber laser oscillator

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