Bringing Topological Light to Chips
The shortest path between two points may be a straight line, but it is not always the easiest. For some systems, including electronics, the easiest path can be around the edges of a material, where impurities will have a reduced impact. Researchers at the Joint Quantum Institute have succeeded in making light take such a topological path, and the approach could one day make it onto photonic chips.
Topological insulators are materials that have the special property of only conducting electrons over their surface and not through their bulk. This results in the electrons travelling with very little resistance because they can flow around impurities. By recreating this effect with photons, light signals can be made to travel with very little lose. What the JQI researchers have accomplished is a photonic array on a chip that does more than just that. Provided the light follows the outside path of the array, it loses very little energy, compared to passing through its interior, but it also will cross the array in a set amount of time. The latter is an important feature as delaying optical signals normally takes optical fiber loops kilometers in length, but this is achieved on a chip.
All of this has also been achieved with great consistency, thanks to the reduced influence of irregularities. That is especially necessary for creating integrated photonic devices as irregularities could lead to device-to-device variations, which would cut into performance.