Engineers find a way to manipulate light at the nanoscale

A scanning electron microscope image of the iron pyrite metasurface created at Rice University to test its ability to bypass the algae base, which describes the trade-off between the material’s optical absorption and how light is refracted. The research shows that virtual reality screens and 3D displays along with optical technologies in general can be improved. Credit: Naik Lab

If you’re going to break a rule with style, make sure everyone sees it. That’s the goal of engineers at Rice University who hope to improve virtual reality displays, 3D displays, and optical technologies in general.

Gururaj Naik, associate professor of electrical and computer engineering at Rice’s George R. Brown School of Engineering and Applied Physics graduate program Chloe Doiron alumna, has found a way to manipulate light at the nanoscale, breaking the Mohs rule, which describes the trade-off between optical absorption of matter and how Refraction of Light.

Apparently, it’s more like a guideline than an actual rule, because there are a number of “Mosian superconductors” out there. Sod’s gold, also known as iron pyrite, is one of them.

to study in advanced optical materialsNike, Doiron and co-author Jacob Khorgen, Professor of Electricity and computer engineering At Johns Hopkins University, he discovered that iron pyrite works well as a nanophotonic material and could lead to better and thinner displays for wearable devices.

Importantly, they devised a method for finding materials that bypass the moss base and provide useful light-handling properties for display and sensing applications.

“In the field of optics, we are still limited to very few materials,” said Nike. “our Periodic Table It is really small. But there is a lot of material that is simply unknown, only because we have not developed any idea how to find it.”

“That’s what we wanted to show: There is physics that can be applied here to shortlist materials, and then help us search for ones that can lead us to any industrial needs,” he said.

“Let’s say I want to design an LED or a waveguide that operates at a certain wavelength, say 1.5 micrometers,” said Nike. “For this wavelength, I want the smallest possible waveguide, which has the lowest loss, which means it can better trap light.”

According to Moss, choosing a material with the highest refractive index at this wavelength usually guarantees success. “This is generally a requirement for all nanoscale photonic devices,” he said. “The materials have to have a bandgap a little bit higher than the desired wavelength, because that’s where we start to see less light going through.”

“Silicon has a refractive index of about 3.4, which is the gold standard,” Nike said. “But we started wondering if we could get past silicon to an index of 5 or 10.”

This prompted their search for other visual options. Therefore, they developed their formula for determining the Mossian super-dielectrics.

“In this work, we provide people with a recipe that can be applied to a publicly available database of material to identify them,” Naik said.

The researchers settled on experiments with iron pyrite after applying their theory to a database of 1,056 compounds, searching three bandgap bands for those with the highest refractive indices. Three compounds along with pyrite have been identified as Mossian superfilters, but pyrite’s low cost and long use in photovoltaic and catalytic applications made it the best choice for experiments.

“False gold has traditionally been studied in astrophysics because it is commonly found in interstellar debris,” Naik said. “But in the context of optics, that’s unknown.”

He noted that iron pyrite has been studied for use in solar cells. “In this context, they showed optical properties In the Visible wavelengths, where it’s really wasteful,” he said. But this was a clue to us, because when something is very lost in the visible frequencies, it likely has a very high refractive index in the near infrared. “

So the lab made a visual score iron pyrite Movies. Material tests revealed a refractive index 4.37 with a 1.03 eV bandgap, exceeding the performance predicted by the Mohs rule by about 40%.

That’s great, Naik said, but the research protocol can – and probably will – find better material.

“There are many candidates, some of whom have not even been submitted,” he said.

Ambient light changes refraction in a two-dimensional material

more information:
Chloe F. Doiron et al, Super Mossian Dielectrics for Nanophotonics, advanced optical materials (2022). DOI: 10.1002 / adom.202201084

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