Topology is a branch of mathematics, which mainly studies the properties of geometric figures or spaces that remain unchanged under continuous deformation. The famous Möbius strip, for example, is a fascinating topological structure.
In topological physics, one of the most important concepts is topological insulators. They behave as insulators in bulk but conduct electricity on surfaces. Inspired by the topological insulators, scientists have proposed photonic analogues, namely photonic topological insulators. Like the electronic counterpart, the photonic topological insulators are opaque in bulk but support one-way waves on surfaces. Such surface waves are topologically robust and could flow though disorder without scattering or losses.
In 2019, Yihao Yang et al. published a paper titled "Realization of a three-dimensional photonic topological insulator" in Nature, which for the first time experimentally verified the three-dimensional (3D) photonic topological insulator. Based on the 3D photonic topological insulator, the research team developed a high-efficiency robust electromagnetic waveguide. Yihao et al. experimentally verified that light could travel through the Z-shaped highly-curved surface effortlessly. The surface of the 3D photonic topological insulator is hence like a "3D highway for photons."
Yihao is also a well-known user of Zhihu, a Chinese version of Quora. He once answered the question "What is a photonic topological insulator?" His answer became a highly upvoted one with "expertise certification". Regarding his research field, he felt that people have begun to get tired of merely new concepts as photonic topological insulators need to find more and better applications.
"Therefore, from this perspective, photonic topological insulators have started the second-half: more researchers who aim to create applications will join in the future," Yihao said.
Dr Yang Yihao has recently finished his postdoctoral work at Nanyang Technological University (NTU), Singapore, and has returned to China to continue his research. Professor Baile Zhang of NTU, a 2012 MIT TR35 honoree, was Yihao's mentor. Eight years later, Yihao is selected by the same list. Perhaps this is the best way to pay tribute to each other.