Phys. Rev. Lett. 109, 106402 (2012)

Look at a quasicrystal close up and it seems to have little pattern. But scale out and an ordered arrangement soon emerges. Yaacov Kraus and colleagues now show that an optical quasicrystal is a means for efficient photon transfer with little loss.

Kraus et al. investigated a one-dimensional quasicrystal comprising a series of microscale optical waveguides side-by-side. They show that light sent down the middle waveguide quickly spreads out to the neighbouring channels as it propagates. If the light is sent down a waveguide on the edge, however, the photons emerge as a tightly localized beam from the guide at the other edge of the quasicrystal.

The researchers highlight that this unexpected effect has many similarities with the electronic properties of topological insulators — where states exist at the surface of an insulating material enabling a current to flow. In both cases, a system with a small number of dimensions displays characteristics associated with a higher-dimensional one. This analogy might aid better understanding of topological states and their application.