All-fiber laser with agile mode-switching capability through intra-cavity conversion

Agile mode switching between LP $_{01}$ and LP $_{11}$ mode in an all-fiber laser is demonstrated by exploiting an acoustically-induced fiber grating within the laser cavity. The laser exploits a cladding pump configuration and can deliver up to 5.85 W of stable output power in LP $_{11}$ mode at 1070.07 nm and 6.06 W in LP $_{01}$ mode at 1070.48 nm, with a slope efficiency near 50%. Complete mode-switching speed with 250 Hz and partial mode-switching speed with 1 kHz are demonstrated. Based on the obtained switching time between LP $_{11}$ and LP $_{01}$ , the maximum complete mode-switching speed is calculated to be ~555.56 Hz. Moreover, variable output beam profiles could be obtained by adjusting the frequency of the modulation signal applied on the acoustically-induced fiber grating. This work could provide an example of realizing a high-power, mode-switchable fiber laser source for practical use.