High-power gain optical fiber capable of simultaneously inhibiting mode instability and nonlinear effect and design method

Abstract

The invention discloses a high-power gain optical fiber capable of simultaneously inhibiting mode instability and a nonlinear effect. The optical fiber is a double-cladding layer and sequentially comprises a fiber core and an inner cladding layer from inside to outside, the fiber core is doped with ytterbium or other rare earth ions to serve as a gain medium, the inner cladding layer is a quartz cladding layer, and the diameter value of the fiber core is 15-100 microns; the numerical aperture NA of the fiber core ranges from 0.01 to 0.1; the cross section of the inner cladding is a regular octagon; the value of the diameter of the inner cladding is 300-1200 microns; the cladding pumping absorption coefficient@915 nm is 0.2 to 1.0 dB / m; the optical fiber is bent and coiled, and the bendingradius is between 2.5 cm and 80 cm. According to the invention, the parameters influencing the thresholds of the nonlinear effect and the mode instability effect in the optical fiber are substituted into the theoretical model for calculation; in combination with the existing process level and experimental conditions, optical fiber parameters and bending radiuses capable of meeting the requirementsof a high-power optical fiber laser and inhibiting gains of a nonlinear effect and a mode instability effect at the same time are selected, and the mode instability threshold and the nonlinear effectthreshold are changed at the same time, so that the maximum output power of the optical fiber is improved.

Description

technical field [0001] The invention belongs to the technical field of optical fiber laser, and in particular relates to a high-power-gain optical fiber and a design method for simultaneously suppressing mode instability and nonlinear effects. Background technique [0002] High-power lasers play an irreplaceable role in many fields such as industrial manufacturing, remote detection, communication transmission, and military equipment. High-power fiber laser combines the advantages of optical fiber and high-power laser, and has the advantages of small size, high power, and good beam quality. At present, it has achieved a single-fiber 2kW near-diffraction-limit output. [0003] In the fiber laser, the gain medium uses a fiber doped with rare earth ions to achieve laser gain output. At present, the most widely used is the Nd (Neodymium) doped silica fiber, which has the advantages of mature technology and stable performance. With the continuous development of fiber materials, y...

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Problems solved by technology

In 2018, Zervas et al. published the document "Power scaling limits in high power fiber amplifiers due to transverse mode instability, thermal lensing, and fiber mechanical reliability" (Proc.SPIE 10512), considering nonlinear effects, mode instability effects and other limiting factors , the model for calculating the highest output power of the optical fiber, but the calculation mode instability threshold in this model is too rough, the accuracy is too low, and it cannot reflect the influence of numerical aperture changes on the mode instability threshold

However, the influence of bending loss is not considered, and the nonlinear effect is not connected to calculate the maximum output power value of the fiber

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