Researchers at the University of Purdue are developing a new class of materials that can serve as basic foundations for advanced optical technologies including ultra-powerful microscopes and highly efficient solar cells.
The new materials called plasmonic metamaterials can achieve an index of refraction less than one or even zero. Refraction is a natural occurrence where electromagnetic waves bend when passing from one material into another.
The researchers believe creating materials that have an index of refraction lower than one holds a range of potential breakthroughs in a budding field called transformation optics.
Alexandra Boltasseva, an assistant professor of electrical and computer engineering at Purdue, says the new materials could allow for nanophotonic devices for a number of applications.
Plasmonic materials could be the key to developing a possible hyperlens that make optical microscopes 10 times more powerful, capable of magnifying extremely small objects such as DNA. These can also be used to develop more advanced sensors.
More importantly, these can lead to new types of light-harnessing systems for more efficient solar cells. By having a very low index of light refraction, plasmonic materials can limit the amount of light lost when solar energy hits a solar cell.
Similarly, scientists at Stanford University believe properly engineered plasmonics can restrict the light that falls on a surface on a sub-micrometric scale, improving the solar light absorption capabilities of ultrathin semiconductor films.
However, development of new technologies based on metamaterials faces critical limitations.
Metamaterials tend to absorb too much light through their silver and gold elements. In addition, these materials also need to be adjusted so they can hold the proper index of refraction.
The researchers are looking to replace silver and gold by infusing more metal impurities into semiconductors to make them more metallic. To achieve the opposite effect, nonmetallic elements can also be added into metal to make them less metallic.
Some of the materials have already been tested and have demonstrated better optical properties than silver and gold.
“These materials can be tailored for almost any application because of their extraordinary response to electromagnetic, acoustic, and thermal waves that transcends the properties of natural materials,” the scientists said in their study.
Ms. Boltasseva, with her colleague Harry Atwater, a professor of applied physics and materials science, co-authored an article on the research that will be published in the journal Science. The work was funded by the United States Army Research Office.