Dynamic modulation of spot-ring mode distribution in a high-power fiber laser utilizing a triple-structure...

High-power spot-ring fiber lasers effectively suppress metal spatter in laser manufacturing such as power battery welding. Increasing expectations regarding processing quality have necessitated the incorporation of additional ring beams to enhance the preheating effect. However, traditional dual-core fiber methods are limited by the waveguide structure. To address this challenge, we propose a dynamic modulation method for spot-ring mode distributions in high-power fiber lasers by utilizing a triple-structure long-period fiber grating (LPFG). The LPFG was temperature-tuned to achieve three types of spot-ring beams with different mode distributions. A triple-structure LPFG was fabricated in a 14/250 fiber, and a kilowatt-level fiber master oscillator power amplifier (MOPA) system was established for verification. Experimental results show that the LPFG can effectively generate Gaussian, spot-single-ring, spot-double-ring, and spot-triple-ring beams with an insertion loss of 0.07 dB. The proposed approach is an effective method for dynamically adjusting the mode distributions in high-power fiber lasers.