Speaker: Thomas Folland, University of Iowa
Abstract: Van der Waals (vdW) crystals offer intriguing light-matter interactions to help us understand their physical properties and develop new optoelectronic technologies. As vdW crystals have a small lateral size and can be exfoliated to atomically thin thicknesses, optical measurements offer some unique challenges for these materials. My group leverages infrared microscopy and nanoscopy to uncover the properties of exfoliated vdW materials and the polaritons that form in these materials. In my talk, I will briefly outline what infrared reflection, transmission, and nearfield spectroscopies can tell us about the properties of van der Waals materials, with a particular focus on the properties of polaritons. We will discuss how the anisotropic crystal structure affiliated with most vdW materials leads to unique optical properties, allowing us to confine light to deeply sub-wavelength length scales. Specifically, we will discuss the optical properties of hBN, MoO3, and ReSe2, where their low symmetry structure gives rise to highly confined polariton modes - compressing light by over an order of magnitude versus the wavelength in free space. Finally, we will show how these techniques can be extended to devices, providing new insights into how material imperfections can influence the performance of devices. This demonstrates that infrared spectroscopic tools can act as metrology tools capable of accessing information unavailable to other techniques.
