Polarization-Maintaining Hollow-Core Fibers for Radially and Azimuthally Polarized Light

Lasers emitting radially and azimuthally polarized beams have been shown for continuous-wave emission as well as for lasers and amplifiers emitting ultrashort laser pulses [1], [2]. Even though the remarkable benefits of using these polarization states in material processing have been experimentally validated [3], [4], they are still rarely used in practice. This can be attributed to the cumbersome but necessary free-space guiding of laser beams with radial and azimuthal states of polarization (SOP), as conventional glass fibers typically do not preserve these SOPs.