Light travels in a straight line. However, scientists have contrived approaches to change the way it travels. A team of researchers from the College of Information Science and Electronic Engineering, Zhejiang University, China, and Nanyang Technological University, Singapore, has now announced the realization of the world’s first three-dimensional (3D) photonic topological insulator. Relevant findings are published in the journal of Nature.

A 3D/2D topological insulator is a material with non-trivial symmetry-protected topological order that has a bulk bandgap, but conducts on its surfaces/edges. More interestingly, the surface/edge states are topological protected and robust against backscattering. It is featured by the exceptional ability to transport electric signals without dissipation, via special quantum states called “topological surface/edge states”.

Inspired by topological insulators, scientists have proposed “photonic topological insulators” in an effort to apply the intriguing idiosyncrasy of topological insulators to the photonic system. In the past, research into photonic topological insulators has been confined to 2D structures.

The team constructs a 3D photonic topological insulator out of a stack of thin plastic sheets embedded with metal antennas acting as tiny electromagnetic resonators. The key breakthrough is made when they realize how to tailor the resonators to interact with electromagnetic waves in a very specific way, granting the waves the desired topological characteristics. Experiments attest to the fact that due to topological protection, transported photons are not affected by impurities, flows or twists, thereby successfully avoiding information dissipation caused by light scattering.

“This research can be applied to 3D topological photonic integrated circuits, waveguides, optical delay lines, lasers and other devices in surface electromagnetic waves,” said CHEN Hongsheng, a team co-supervisor from Zhejiang University.

“Our work extends the family of 3D topological insulators from fermions to bosons and may inspire the realization of 3D topological insulators in other bosonic systems, such as acoustic and mechanical structure”，said Dr. Yihao Yang, the lead author of this work.

This work might be beneficial for future researches on photonic chips and photon computers. In the future, in a tiny photonic chip, information-laded light can travel fast on crisscrossed photonic highways, creating a faster and better world.