Cut-off, "forbidden" fiber modes: a new regime of light propagation

Since the elucidation of total internal reflection by Colladon, Babinet and Tyndall over 150 years ago, bound states of light have been the primary means to transport light, whether on a chip or in optical fibers. We show that light carrying sufficiently high orbital angular momentum can create a centrifugal barrier for itself, thereby enabling guidance even in a regime where a mode is normally considered “cutoff,” that is, in a regime where bound states are conventionally forbidden. We will discuss how this discovery, which has parallels with why binary stars don’t collapse into each other due to gravity, has applications in diverse areas, including classical and quantum communications with high dimensionality, power scaling of fiber lasers and nonlinear optics with greater degrees of freedom.