Helical Bragg Gratings: Experimental Verification of Light Orbital Angular Momentum Conversion

Structured light, in particular light possessing orbital angular momentum (OAM), has been actively studied in recent decades. Helical Bragg grating (HBG) is a reflecting optical element, which predicted to be able to convert the OAM of light in waveguides and fibers. However, the HBG has not been demonstrated experimentally yet. Here we report the first experimental manifestation of HBG created in...