Controlling light with electric fields could create invisibility cloaks

(Credit: iStock)
(Credit: iStock)

A new technique for controlling light with electric fields could make you disappear, or plunge you into a virtual world with no need for goggles.

Researchers from North Carolina State University used electric fields to tune the refractive index of a semiconductor, allowing them to change the behaviour of light passing through it. “Our method is similar to the technique used to provide the computing capabilities of computers,” says Linyou Cao, an assistant professor of materials science and a corresponding author of the work, which was published in the journal Nano Letters.

In computers, an electric field can turn a current either on or off – corresponding to the 1s and 0s that make up binary code. According to the researchers, this new discovery will allow them to do something similar with light. “A light may be controlled to be strong or weak, spread or focused, pointing one direction or others by an electric field,” says Cao.

“We think, that just as computers have changed our way of thinking, this new technique will likely change our way of watching.”

The ability to shape light into arbitrary patterns opens up a world of potential applications, according to Cao. These could include virtual reality that works without goggles, movies that float in front of your eyes, or even an invisibility cloak that can bend light away from you to make you disappear.

Before this discovery, previous attempts to change the refractive index of materials with electric fields only managed tiny amounts of change – between 0.1 and 1% at most. But the group from North Carolina were able to change the refractive index (how much light passing through an object bends) by 60 per cent, using thin films molybdenum sulphide, tungsten sulphide and tungsten selenide.”

“This is only a first step,” said Cao. “We think we can optimize the technique to achieve even larger changes in the refractive index. And we also plan to explore whether this could work at other wavelengths in the visual spectrum.”

A new technique for controlling light with electric fields could make you disappear, or plunge you into a virtual world with no need for goggles.

Researchers from North Carolina State University used electric fields to tune the refractive index of a semiconductor, allowing them to change the behaviour of light passing through it. “Our method is similar to the technique used to provide the computing capabilities of computers,” says Linyou Cao, an assistant professor of materials science and a corresponding author of the work, which was published in the journal Nano Letters.

In computers, an electric field can turn a current either on or off – corresponding to the 1s and 0s that make up binary code. According to the researchers, this new discovery will allow them to do something similar with light. “A light may be controlled to be strong or weak, spread or focused, pointing one direction or others by an electric field,” says Cao.

“We think, that just as computers have changed our way of thinking, this new technique will likely change our way of watching.”

The ability to shape light into arbitrary patterns opens up a world of potential applications, according to Cao. These could include virtual reality that works without goggles, movies that float in front of your eyes, or even an invisibility cloak that can bend light away from you to make you disappear.

Before this discovery, previous attempts to change the refractive index of materials with electric fields only managed tiny amounts of change – between 0.1 and 1% at most. But the group from North Carolina were able to change the refractive index (how much light passing through an object bends) by 60 per cent, using thin films molybdenum sulphide, tungsten sulphide and tungsten selenide.”

“This is only a first step,” said Cao. “We think we can optimise the technique to achieve even larger changes in the refractive index. And we also plan to explore whether this could work at other wavelengths in the visual spectrum.”

Professor Dan Hewak at the University of Southampton’s Optoelectronics Research Centre, who was not connected with the research, told Professional Engineering it represented a “significant step forward” in the field.

“The material offers an opportunity to link optical devices and electronic devices with one fundamental material family,” he said.  “Right now we have silicon chips in our computers but these silicon chips can’t really generate light so they’re used only for electronics and not for displays and optical applications. But these 2D materials are very good electronic materials, but they can also emit light. They provide a link between those two domains.”

This simplifies the electronics, said Hewak, and could lead to lighter, smaller and more efficient devices in future.

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