In a recent study published in Advanced Optical Materials, a team of researchers led by Rice University discovered a method to identify nanophotonic materials with the prospective of improving screens used for 3D and virtual reality displays and optical technologies overall.
By manipulating light at nanoscale levels, the researchers effectively broke what’s known as the Moos rule, which expresses a trade-off between the optical absorption of a material and how the light it refracts. For the study, they discovered that iron pyrite, also known as Fool’s gold, works specifically well as a nanophotonic material which could lead to both thinner and better displays for wearable devices.
More importantly, they’ve created a method for discovering materials that exceed the Moss rule and provide useful light-handling properties for sensing applications and displays.
"In optics, we're still limited to a very few materials," said Dr. Gururaj Naik, an associate professor of electrical and computer engineering at Rice University’s George R. Brown School of Engineering and a co-author on the study. "Our periodic table is really small. But there are so many materials that are simply unknown, just because we haven't developed any insight on how to find them. That's what we wanted to show: There are physics that can be applied here to short-list the materials, and then help us look for those that can get us to whatever the industrial needs are. Let's say I want to design an LED or a waveguide operating at a given wavelength, say 1.5 micrometers. For this wavelength, I want the smallest possible waveguide, which has the smallest loss, meaning that can confine light the best."
The research team applied their hypothesis to a database of 1,056 compounds and searched in bandgap ranges for compounds containing the highest refractive indices. Along with the pyrite, three compounds were found to act as what’s known as “super-Mossian” candidates. However, it was the both the low cost and longevity of pyrite in catalytic and photovoltaic applications that made it the best choice for the experiments. In the end, the tests revealed the material exceeded the Moss rule by about 40 percent.
Naik said while this is great, he noted the search protocol could -- and likely will -- find materials that are even better.
Sources: Advanced Optical Materials
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