Super-Mossian Dielectrics for Nanophotonics


High refractive index dielectrics enable nanoscale integration of optical components with practically no absorption loss. Hence, high index dielectrics are promising for many emerging applications in nanophotonics. However, the lack of a complete library of high index dielectric materials poses a significant challenge to understanding the full potential for dielectric nanophotonics.

If you’re going to break a rule with style, make sure everybody sees it. That’s the goal of engineers at Rice University who hope to improve screens for virtual reality, 3D displays and optical technologies in general. Researchers found a way to manipulate light at the nanoscale that breaks the Moss rule, which describes a trade-off between a material’s optical absorption and how it refracts light. The research team find iron pyrite works particularly well as a nanophotonic material and could lead to better and thinner displays for wearable devices. More important is that they’ve established a method for finding materials that surpass the Moss rule and offer useful light-handling properties for displays and sensing applications. 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. Choosing a material with the highest possible refractive index at that wavelength would normally guarantee success.

The researchers settled on experiments with iron pyrite after applying their theory to a database of 1,056 compounds, searching in three bandgap ranges for those with the highest refractive indices. Three compounds along with pyrite were identified as super-Mossian candidates, but pyrite’s low cost and long use in photovoltaic and catalytic applications made it the best choice for experiments. The authors noted iron pyrite has been studied for use in solar cells. In that context, they showed optical properties in the visible wavelengths, where it’s really lossy, he said. But that was a clue for us, because when something is extremely lossy in the visible frequencies, it’s likely going to have a very high refractive index in the near-infrared. So the lab made optical-grade iron pyrite films. Tests of the material revealed a refractive index of 4.37 with a band gap of 1.03 electron volts, surpassing the performance predicted by the Moss rule by about 40%.

Super-Mossian Dielectrics for Nanophotonics - Advances in Engineering

About the author

Jacob Khurgin, a professor of electrical and computer engineering, is known for his diverse and eclectic research in the areas of optics, electronics, condensed matter physics, and telecommunications.

Much of Khurgin’s work lies at the intersection of optics and solid-state electronics. He has focused on an array of topics during his career, including the optics of semiconductor nanostructures, nonlinear optical devices, lasers, optical communications, microwave photonics, and condensed matter physics. His most recent work involves mid-infrared optical frequency combs, metamaterials, optical refrigeration of solids, and phonon engineering for high-frequency transistors, to name a few.

The insights that have emerged from his research have led to numerous inventions ranging from small appliances, such as electric shavers and coffeemakers, to sophisticated systems for laser communication and chemical detection. He has published roughly 40 patents to date.

Khurgin has consulted for numerous companies over the years, including Philips Electronics, IBM, AT&T, and Hewlett Packard. His work has been funded by the Defense Advanced Research Projects Agency (DARPA), Air Force Office of Scientific Research (AFOSR), Office of Naval Research, National Science Foundation, NASA, and Small Business Technology Transfer (STTR).

He is a member of the American Physical Society Joint Council on Quantum Electronics and has served as a technical program committee member for more than 60 academic conferences. He has held visiting professorships at numerous institutions, including Princeton, UCLA, Brown, ETH in Zurich, and Ecole Normale Superieure in Paris. He was named a Fellow by the American Physical Society and the Optical Society of America.

Khurgin is an associate editor for Optica, a premier journal of Optical Society of America. He has published eight book chapters, 340 papers in refereed journals, and a book: “Slow Light – Science and Applications.”


Chloe F. Doiron, Jacob B. Khurgin, Gururaj V. Naik, Super‐Mossian Dielectrics for Nanophotonics, Advanced Optical Materials (2022). DOI: 10.1002/adom.202201084

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