Stuttgart and IIT team canalizes light in MoOCl2 without fabricated waveguides

Researchers at the University of Stuttgart 4th Physics Institute and the Istituto Italiano di Tecnologia in Milan demonstrated a mechanism for directing light in a naturally hyperbolic van der Waals material without conventional nanofabricated waveguides, phys.org reported. The work is published in Nature Nanotechnology. A team led by Professor Harald Giessen and Dr. Antonio Ambrosio used two-dimensional molybdenum oxy-dichloride (MoOCl2). By placing a nanoscale gold antenna on the surface and illuminating it with infrared laser light, they generated highly confined optical waves that propagated along a single direction, remaining confined as if guided by an invisible waveguide. Doctoral researcher Farid Aghashirinov and postdoctoral fellow Andrea Mancini carried out the experiments with scattering-type scanning near-field optical microscopy. MoOCl2 is biaxial: along one axis it supports surface plasmons, while the orthogonal direction is dielectric and suppresses propagation, producing canalized channels from crystal properties rather than lithography. Near 4 μm, canalized propagation occurs; changing wavelength produces isotropic ringlike or open hyperbolic wavefronts, enabling tunable on-chip light routing, according to the report. The approach is positioned for integrated photonics, on-chip optical communication, and quantum technologies.