Bhaskar Abhiraman (VIPER '21) Publishes in Nature Communications

Hybrid exciton-plasmon-polaritons in van der Waals semiconductor gratings

Nature Communications | Published July 2020 | Full Article

Also see "Suppression of Exciton Absorption via Structural Coloration: Manipulating Color with Nanophotonics" on Bhaskar's website. 


By Bhaskar Abhiraman (VIPER '21)


After my freshman summer, I worked with Professor Aaswath Raman on manipulating structures to optimize their properties in the infrared regime. That was when I began wrapping my head around light as electromagnetic radiation and got experience with computational physics. When I joined the Jariwala group, I found that they were exploring a similar type of geometry which was instead optimized to exhibit interesting behavior for visible light wavelengths. The first author, PhD student Huiqin Zhang, is an expert at experiments and fabrication of these nanostructures. Meanwhile, I was able to jump in on simulations and analysis. We were examining reflection spectra of parallel WS2 strips on a gold substrate. The WS2 was only tens of atoms thick, and the strips were spaced out at optical wavelengths. Normally, WS2 intrinsically absorbs an orange wavelength due to its semiconductor band structure. However, due to the periodicity we introduced, we also observed structural color, color that results from geometry and not just material properties. For example, iridescent bird feathers and butterfly wings can get their color from nanostructures on their surfaces. In our experiments and simulations, we observed coupling of this structural color to that intrinsic absorption. In some cases, this caused the intrinsic absorption to disappear—a new finding! To model this coupling and the subsequent disappearance of intrinsic absorption, we applied a coupled oscillator model. In some physics courses, you might come across nasty, ridiculous problems with a mess of springs and pendulums. They seem absurd, but the exact same mathematics that governs those kinds of mechanical systems was applied to our model, and was able to replicate the disappearance effect we observed! It's beautiful that this seemingly ridiculous analogy connects mechanics to nanophotonics. 


I'm grateful to the VIPER program for supporting this work. I'm also extremely lucky to have worked with Professor Jariwala, who takes mentorship and promotion of student work very seriously.