Switching High-Order Modes in DSR Fiber Laser Using Acoustically Induced Fiber Grating

A high-energy dissipative soliton resonance (DSR) Yb-doped fiber laser with watt-level average power of high-order modes switching output is developed. Stable intracavity oscillations of diverse orders of high-order modes are facilitated by incorporating two mode conversion schemes: acoustically induced fiber grating (AIFG) and its cascading with fiber long-period gratings (broadband long-period fiber grating cascaded AIFG). The first AIFG enables conversion from LP₀₁ mode to LP₁₁ mode with a conversion efficiency of 92%, while the second AIFG converts LP₁₁ mode to LP₂₁ mode with a conversion efficiency of 64%, with less than a millisecond-scale mode-switching time. In addition, a few-mode picosecond seed laser amplifier with the AIFG for power amplification of LP₁₁ and optical vortex beam (OVB) modes while maintaining high purity is demonstrated experimentally. These works significantly enhance the diversity of high-order modes in high-energy Yb-doped fiber lasers, particularly in their capability for high-order modes switching output.