Beams carrying orbital angular momentum (OAM) are attractive as they offer a theoretically unbounded number ofdiscrete states and have therefore been a subject of great interest for a variety of fundamental and applied researchincluding optical communications, optical trapping, super-resolution microscopy, remote sensing and quantuminformation. In this work, we present a study on the use of fused silica capillary optical fibers for OAM beampropagation by means of antiresonant reflecting waveguiding. In particular, we propose the application of these simpleand commercially available fibers for probing the light–matter interactions within the hollow core. We show that OAMbeams (topological charge |L| = 1) of high mode purity (>90%) can be achieved in such capillary fibers. The stability ofthe OAM beam propagation was theoretically and experimentally demonstrated in the visible range. A numerical studybased on full-vector finite-element method is conducted to characterize the change of OAM mode purity and loss as afunction of the refractive index (RI) of the material filling the core. The propagation loss remains in the range of a fewdB/m throughout the range of RI values varying from 1 to 1.39 that encompasses many analytes in the vapor or liquidphase. Finally, we propose that the simple capillary fiber can be used as a cost-effective optofluidic platform to studyOAM light-matter interactions and new optical phenomena involving biochemical analytes.
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