Cylindrical vector beam generation based on arc-induced long period gratings in few-mode fiber
We propose and demonstrate the use of the cost-effective electric arc writing method for the all-fiber CVB and OAM mode generation in few-mode fibers 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 \(\mu m\), such 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 LPFG are elucidated and we report a polarization-dependent loss of about 2.5 dB accross the different CVBs. By means of a fabricated LPFG, we further demonstrated the all-fiber generation of the OAM states with topological charge (\(\pm1\)) at the output of the few-mode fiber. The results are relevant to the fields of laser material processing, space-division multiplexing and novel optical sensors that would benefit from a compact source of quality CVB and OAM beams of high average optical power.