A newly designed device routes photons along twisting paths with minimal scattering by exploiting ‘topological’ effects. In physics, topological properties are those that do not change when a shape is deformed; as such, they can preserve the direction of electrical currents and protect light waves from disturbances.
Mohammad Hafezi and his collaborators at the University of Maryland in College Park etched triangular holes into a transparent slab of insulating material. The holes, which were arranged in a honeycomb pattern, were slightly larger in one half of the slab than in the other, a design that gave the two sections different topological properties.
Thanks to this split, single photons emitted by a light source in the slab could travel only along the boundary between the sections. The device’s design also prevented the light from scattering when it swerved around bends and forced polarized light to travel in only one direction.