Topological photonic crystal made of silicon

A new principle, in which electromagnetic waves, including light, can propagate on the edge of a 2D photonic crystal without being scattered, has been developed by researchers from Japan’s International Center for Materials Nanoarchitectonics (MANA) and the National Institute for Materials Science (NIMS).

It was known that scattering of light by defects in conventional photonic crystals could be suppressed in topological photonic states, but so far special materials were required in order to create topological photonic crystals.

However, in the new approach, called topological nanoarchitectonics, the MANA researchers are said to have realised a topological photonic crystal by merely adjusting the positions of insulator or semiconductor nanorods in a honeycomb lattice.

When hexagonal clusters are formed by adjusting the positions of nanorods, electromagnetic modes carrying spin appear. As a result, the MANA researchers theoretically clarified that a photonic crystal exhibits topological properties when the separation between hexagonal clusters is narrowed from that of the honeycomb lattice.

The discovery could lead to the development of new functions and devices through integration with semiconductors.