Single-longitudinal-mode DBR fiber laser with cylindrical vector beam output based on Yb³⁺-doped YAG crystal-derived...

A single-longitudinal-mode (SLM) distributed Bragg reflector (DBR) fiber laser with cylindrical vector beam (CVB) output at 1064 nm was demonstrated. The SLM operation is enabled by a short DBR cavity constructed by a high-gain Yb:YAG crystal-derived silica fiber (YYCDSF), fabricated via the molten core (MC) method with a core Yb₂O₃ concentration of 7.43 wt.%. By offset-splicing a 5.4-mm segment of the YYCDSF to a few-mode fiber Bragg grating (FM-FBG) for mode excitation and selection, a stable single-longitudinal-mode cylindrical vector beam (SLM-CVB) fiber laser was achieved. The laser delivered a maximum output power of 18.08 mW, a slope efficiency of 12.3% for the absorbed pump power, and an optical signal-to-noise ratio (OSNR) of ∼56 dB. Furthermore, by adjusting the polarization controller (PC), switchable radially polarized (TM₀₁) beam and azimuthally polarized (TE₀₁) beam were generated, both exhibiting mode purities (MP) exceeding 93%. To the best of our knowledge, this is the first SLM-CVB fiber laser demonstration based on a DBR cavity structure.