A new method of dispersion-regulated soliton group pulses for efficient mid-infrared fiber laser generation

High-power mid-infrared (MIR) lasers have aroused great interest in many scientific and industrial applications. Due to the immaturity of pump sources and fiber materials, it has been difficult to achieve high-power laser output in MIR long-wavelength spectrum (LWS) exceeding 2.4 μm using traditional schemes. Here, we propose a new method for generating MIR laser that utilizes the dispersion characteristics of nonlinear fiber to segmentally regulate the frequency-shift, accumulation, and enhancement process of soliton group pulses, in order to maximize pump energy conversion and reshape spectral profile. A 14.72 W high-power all-fiber MIR laser was obtained using a fluorotellurite fiber with dispersion specifically engineered as a frequency-shift stretcher. The laser conversion efficiency reached 70%, facilitating efficient energy conversion from 2 μm near-infrared laser to 3 μm mid-infrared laser. Notably, the proportion of MIR LWS exceeding 2.4 μm was significantly enhanced, accounting for over 90% of the total spectrum components. This work provides a simple, compact, efficient, stable and economical method for developing high-power, high-efficiency, and high-occupancy MIR fiber lasers, without the need for complex MIR amplification systems, which is of great scientific significance for promoting the practical application of 3-5 μm MIR light sources.