Researchers Manipulate Light to Make Optical Chip Invisible

Using a metasurface and an integrated photonics platform, researchers have conceived a method of achieving invisibility cloaks by tailoring evanescent fields. The approach deflects and scatters light away from a ‘cloaking’ chip surface so it is not detected. The scattering fields of the object located on the cloak do not interact with the evanescent field, rendering the object invisible.

To design a plasmonic waveguide-based invisibility cloaking scheme, Ben-Gurion University of the Negev (BGU) researchers performed an analysis of the modal distribution and surface intensity in a channel photonic waveguide with a metasurface overlayer. The spatial distribution of the metasurface permittivity was analytically calculated based on transformation optics principles. The spatial distribution was then imported into a commercial Maxwell solver using the finite-difference time-domain method (FDTD).

Researchers demonstrated cloaking for a cylindrical object with diameter of 70 percent from the waveguide width on a high index ridge waveguide structure with a silicon nitride guiding layer on silica substrate.

“We showed that it is possible to bend the light around an object located on the cloak on an optical chip. The light does not interact with the object, thus resulting in the object’s invisibility,” said Alina Karabchevsky, head of BGU’s Light-on-a-Chip Group.

An operational cloaking chip could be an extension of technologies such as radar-absorbing dark paint used on stealth aircraft, local optical camouflage, surface cooling to minimize electromagnetic IR emissions, or electromagnetic wave scattering.

“These results open the door to new integrated photonic devices, harnessing electromagnetic fields of light at nanoscale for a variety of applications from on-chip optical devices to all-optical processing,” Karabchevsky said.

The researchers’ next step will be to develop a prototype.

The research was published in Scientific Reports (doi: 10.1038/s41598-017-10578-6).