Novel semiconductor structure bends light 'wrong' way -- the right direction for many applications

Oct 14, 2007
Novel semiconductor structure bends light 'wrong' way
An easy-to-produce material made from the stuff of computer chips has the rare ability to bend light in the opposite direction from all naturally occurring materials. The semiconductors that constitute the Princeton invention are grown from crystals using common manufacturing techniques, making it less complex, more reliable and easier to produce than other metamaterials. Credit: Keith Drake

A Princeton-led research team has created an easy-to-produce material from the stuff of computer chips that has the rare ability to bend light in the opposite direction from all naturally occurring materials. This startling property may contribute to significant advances in many areas, including high-speed communications, medical diagnostics and detection of terrorist threats.

The new substance is in a relatively new class of materials called "metamaterials," which are made out of traditional substances, such as metals or semiconductors, arranged in very small alternating patterns that modify their collective properties. This approach enables metamaterials to manipulate light in ways that cannot be accomplished by normal materials.

Previous metamaterials were two-dimensional arrangements of metals, which limited their usefulness. The Princeton invention is the first three-dimensional metamaterial constructed entirely from semiconductors, the principal ingredient of microchips and optoelectronics.

"To be useful in a variety of devices, metamaterials need to be three-dimensional," said Princeton electrical engineering professor Claire Gmachl, one of the researchers on the study. "Furthermore, this is made from semiconductors, which are extremely functional materials. These are the things from which true applications are made."

The research team, led by Princeton engineering graduate student Anthony Hoffman, will publish its findings online Oct. 14 in the journal Nature Materials. Other Princeton researchers on the team include graduate students Leonid Alekseyev, Scott Howard and Kale Franz; former Council of Science and Technology fellow Dan Wasserman, now at the University of Massachusetts-Lowell; and former electrical engineering professor Evgenii Narimanov, now at Purdue University. The team also includes collaborators from Oregon State University and telecommunications firm Alcatel-Lucent.

Light waves and other forms of electromagnetic radiation bend whenever they pass from one medium to another. This phenomenon, called refraction, is readily observable when a straw placed into a glass of water appears to be bent or broken. Lenses in reading glasses or a camera work because of refraction.

All materials have an index of refraction, which measures the degree and direction that light is bent as it passes through them. While materials found in nature have positive refractive indices, the material recently invented by Princeton researchers has a negative index of refraction.

In the case of the straw in a glass, normal water would make the underwater portion of the straw appear to bend toward the surface. If water were able to refract light negatively, as the newly invented semiconductor does, the segment of straw under the water would appear as if it were bending away from the surface

Far more than a neat optical illusion, negative refraction holds promise for the development of superior lenses. The positive refractive indices of normal materials necessitate the use of curved lenses, which inherently distort some of the light that passes through them, in telescopes and microscopes. Flat lenses made from materials that exhibit negative refraction could compensate for this aberration and enable far more powerful microscopes that can "see" things as small as molecules of DNA.

In addition, the Princeton metamaterial is capable of negative refraction of light in the mid-infrared region, which is used in a wide range of sensing and communications applications. Its unique composition results in less lost light than previous metamaterials, which were made of extremely small arrangements of metal wires and rings. The semiconductors that constitute the new material are grown from crystals using common manufacturing techniques, making it less complex, more reliable and easier to produce.

"Currently, the typical infrared lens is a massive object -- the setups are bulky," Hoffman said. "This new material may enable more compact mid-infrared optics because we now have a new material with an entirely new set of optical parameters in our toolkit."

The research is part of a multi-institutional research center called Mid-Infrared Technologies for Health and the Environment (MIRTHE). Researchers at MIRTHE are developing compact sensors that detect trace amounts of gases in the atmosphere and human breath. These could one day be used in devices that monitor air quality and enhance homeland security, as well as in non-invasive and on-the-spot medical tests for diabetes and lung disease.

The research relies on a new type of laser that emits mid-infrared light. Gmachl, who directs the MIRTHE project, said the new material could be used to make the lasers better and smaller.

Next, the team plans to incorporate the new metamaterial into lasers. Additionally, the researchers will continue to modify the material in attempts to make features ever smaller in an effort to expand the range of light wavelengths they are able to manipulate.

Source: Princeton University

Explore further: Technique simplifies the creation of high-tech crystals

add to favorites email to friend print save as pdf

Related Stories

Technique simplifies the creation of high-tech crystals

16 hours ago

Highly purified crystals that split light with uncanny precision are key parts of high-powered lenses, specialized optics and, potentially, computers that manipulate light instead of electricity. But producing ...

New particle-sorting method breaks speed records

Jun 24, 2014

Researchers compare the processing of biological fluid samples with searching for a needle in a haystack—only in this case, the haystack could be diagnostic samples, and the needle might be tumor cells ...

A collaboration of minds and metal

Jun 24, 2014

This past January, Derek Ahneman, a graduate student in the lab of Abigail Doyle, a Princeton University associate professor of chemistry, began work on an ambitious new project: he proposed the merger of ...

Experts cast doubt on Big Bang bolstering discovery

Jun 14, 2014

Astrophysicists are casting doubt on what just recently was deemed a breakthrough in confirming how the universe was born: the observation of gravitational waves that apparently rippled through space right ...

Has dust clouded the discovery of gravitational waves?

Jun 04, 2014

It's almost three months since a team of scientists announced it had detected polarised light from the afterglow of the Big Bang. But questions are still being asked about whether cosmic dust may have clou ...

Recommended for you

Unleashing the power of quantum dot triplets

1 hour ago

Quantum computers have yet to materialise. Yet, scientists are making progress in devising suitable means of making such computers faster. One such approach relies on quantum dots—a kind of artificial atom, ...

Chemist develops X-ray vision for quality assurance

2 hours ago

It is seldom sufficient to read the declaration of contents if you need to know precisely what substances a product contains. In fact, to do this you need to be a highly skilled chemist or to have genuine ...

The future of ultrashort laser pulses

2 hours ago

Rapid advances in techniques for the creation of ultra-short laser pulses promise to boost our knowledge of electron motions to an unprecedented level.

IHEP in China has ambitions for Higgs factory

19 hours ago

Who will lay claim to having the world's largest particle smasher?. Could China become the collider capital of the world? Questions tease answers, following a news story in Nature on Tuesday. Proposals for ...

The physics of lead guitar playing

21 hours ago

String bends, tapping, vibrato and whammy bars are all techniques that add to the distinctiveness of a lead guitarist's sound, whether it's Clapton, Hendrix, or BB King.

User comments : 0