Scientists invented the smallest known way to guide light

2D optical waveguides could point way to new technology.


Fiber optic cables carry light that encodes everything, all inside strands about the size of a hair. What would happen if you made even thinner and flatter strands—in effect, so thin that they’re 2D instead of 3D? What would happen to the light?

These questions puzzled the University of Chicago, Prof. Jiwoong Park.

He and his team discovered that only a few thick glass crystal sheet atoms could catch and convey light through a series of inventive tests. In addition, it was remarkably effective and had a range of up to a centimeter, which is a great distance in light-based computing. The study demonstrated 2D photonic circuits and could open paths to new technology.

Scientists were surprised to see the power of this super-thin crystal: It can hold energy and deliver it a thousand times further than anyone has seen in similar systems.

The recently developed system is a two-dimensional waveguide used to direct light. In testing, the scientists discovered they could direct the light’s path through a chip using incredibly tiny prisms, lenses, and switches—all the components needed for circuits and computations.

With this system, the glass crystal is thinner than the photon itself—so part of the photon sticks out of the crystal as it travels.

Along the trip, the photons can gather information about the surroundings. Consider checking the suitcases brought in from outside to see if it is snowing there. Scientists can even envision creating minuscule sensors using these waveguides.

Park said, “For example, say you had a sample of liquid and wanted to sense whether a particular molecule was present. You could design it so that this waveguide travels through the sample, and the presence of that molecule would change how the light behaves.”

The scientists are also interested in creating extremely thin photonic circuits that might be layered to incorporate numerous tiny devices into the same chip area. Molybdenum disulfide was the glass crystal employed in these studies, but the concepts should also apply to other substances.

Journal Reference:

  1. Myungjae Lee, Hanyu Hong et al. Wafer-scale δ waveguides for integrated two-dimensional photonics. Science. DOI: 10.1126/science.adi2322