Researchers Use Glass to Make Objects Disappear

Researchers are developing a new approach to crafting a mythical cloak of invisibility that uses glass rather than metal or pure silicon.

A material that could deflect light waves around itself and effectively render the wearer, a shrouded object or a spaceship invisible remains the stuff of Harry Potter and Star Trek fantasy .

Nevertheless, scientists are making progress with a range of so-called metamaterials, or artificial materials having properties that do not exist in nature. These cloaking devices, which have successfully shielded objects from certain wavelengths of light, have been made from metal rings, wires, silicon "carpets," and other shapes and substances.

"Ours is the first to do the cloaking of cylindrical objects with glass," said Elena Semouchkina, lead author of a new study in Applied Physics Letters. Semouchkina is an associate professor of electrical and computer engineering at Michigan Technological University and an adjunct professor at the Pennsylvania State University

Glass cloaking device

In the paper, she and her colleagues describe developing a nonmetallic cloak that uses identical glass resonators made of chalcogenide glass, a type of "dielectric" material that does not conduct electricity.

The tiny glass resonators are arranged in a concentric pattern in the shape of a cylinder. The "spokes" of the concentric configuration produce the magnetic resonance required to bend light waves around an object, making it invisible.

In computer simulations, the cloak made objects hit by infrared waves – longer, less energetic waves than the light that our eyes see – disappear from view.

Invisibility by other means

Semouchkina and her team are also testing an invisibility cloak rescaled to work at microwave frequencies and made of ceramic resonators. For the work, the researchers are using a cave-like compartment called an anechoic chamber at Michigan Tech that is lined with highly absorbent charcoal-gray foam cones.

In this chamber, antennas transmit and receive microwaves, which are much longer than infrared light. The researchers have successfully cloaked metal cylinders two to three inches (five to 7.6 centimeters) in diameter and three to four inches (7.6 to 10.2 centimeters) high.

"Starting from these experiments, we want to move to higher frequencies and smaller wavelengths," Semouchkina said. "The most exciting applications will be at the frequencies of visible light."

As for whether an aspiring wizard or a future spacecraft will be able to clandestinely "cloak" themselves someday, "it is possible in principle, but not at this time," Semouchkina said.

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