Cylindrical vector beam generation based on arc-induced long-period gratings in few-mode fiber

Abstract

We propose and demonstrate the use of the cost-effective electric arc writing method for the all-fiber cylindrical vector beam (CVB) and orbital angular momentum (OAM) beam generation in few-mode fibers (FMFs) for the first time to the best of our knowledge. We show that this technique enables the writing of long-period fiber gratings (LPFGs) with pitch values as small as 238 μm, which is required in some high-index contrast specialty fibers tailored for the stable guiding of CVB and OAM modes. Conversion efficiencies around 81% are measured for three different symmetric CVBs. The polarization-dependent properties of the fabricated gratings are elucidated, and we report a polarization-dependent loss of about 2.5 dB across the different CVBs. By means of a fabricated LPFG, we further demonstrated the all-fiber generation of the OAM states with topological charge (±1) at the output of the FMF. The results are relevant to the fields of space-division multiplexing, optical sensors, and optical tweezers that would benefit from a compact source of quality CVB and OAM beams of high average optical power.