Light journeys unimpeded along material’s surface | Matter & Energy | Science News


Light journeys unimpeded along material’s surface | Matter & Energy | Science News.

– extracts from the article –

Topological insulators have been a burgeoning area of condensed-matter physics since they were proposed in 2005 (SN: 5/22/10, p. 22). Typical materials are either conductors or insulators, but topological insulators such as bismuth telluride are exotic hybrids: They block electric current yet allow electrons to flow along their surfaces.

What’s more, these surface electrons can move unimpeded through bumps and grooves that would normally block their path. That useful property makes topological insulators intriguing candidates for future electronics.

The ability to enable electrons to surf along the surface and avoid obstacles is so enticing that some physicists have investigated whether other particles, particularly photons, could do the same thing. Along with electrons, photons are an essential element of modern technology. Electrons flow through chips in our computers and smartphones, while photons are the information carriers that enable high-speed communication over fiber-optic cables. The key to faster, more efficient communication networks is minimizing the scattering of photons when they encounter obstacles.

With that goal in mind, physicist Mordechai Segev and his team at the Technion-Israel Institute of Technology in Haifa set out to demonstrate the first photonic topological insulator. They started with a block of glass and etched in hundreds of helical waveguides, which are essentially wires for light. The waveguides were tightly packed in a honeycomb-like structure so that light trying to make its way through one waveguide interfered with light in the others and canceled out.

The only part of each waveguide that did not cancel out light was its outer edge. As a result, photons got steered along the outside of the bundle of waveguides, confining them to the surface of the glass block.

When the researchers shined a beam of red light on one face of the glass, the photons moved along the surface of the glass, easily made a turn once they reached an edge of the glass and then continued on their way along the surface. None of the light got scattered by surface imperfections.


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