Photopolymerization, the process of using ultraviolet light to activate polymerization within resins, is a powerful approach to create arbitrary, transparent micro-objects with a resolution below the diffraction limit. We investigate photopolymerization of ultraviolet curing resins with a light field possessing orbital angular momentum (OAM). Due to total internal reflection of the beam within the cured polymer, the material acts as a waveguide, which develops into an optical fibre as long as submillimeters. Importantly, the cured polymer mirrors the energy flow and helical nature of the incident OAM field, resulting in an equivalent spiralling of the cured polymer waveguide itself. Moreover, the chirality of the helix, which is the direction of the spiral, can be controlled by inverting the handedness (reversing the sign of the azimuthal index or topological charge) of the incident field. As the fibre diameter becomes narrower due to self-focusing effects, incident light with higher topological charge cannot be maintained within the single-mode structure of the fibre. We show that the fibre repeatedly branches into a bundle of intertwined fibre guides, each of which carries a fundamental mode of the OAM. Such fibre structures represent a novel form of photonic lanterns. This research opens up a range of new vistas and has broad consequences for the fields of structured light, new approaches to writing novel mesoscopic structures and applications such as in detecting or sorting the OAM mode in areas including optical communications and manipulation.
Yoshihiko Arita, Junhyung Lee, Shunsuke Toyoshima, Katsuhiko Miyamoto, Kishan Dholakia, and Takashige Omatsu, "Generation of helical microfibers by photopolymerization of UV curing resins through light fields possessing orbital angular momentum (Conference Presentation)," Proc. SPIE 10549, Complex Light and Optical Forces XII, 1054917 (Presented at SPIE OPTO: February 01, 2018; Published: 14 March 2018); https://doi.org/10.1117/12.2290479.5751542203001.
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