Mid‐ to Far‐Infrared Anisotropic Dielectric Function of HfS2 and HfSe2
Abstract
The far‐infrared (far‐IR) remains a relatively underexplored region of the electromagnetic spectrum extending roughly from 20 to 100 µm in free‐space wavelength. Research within this range has been restricted due to a lack of optical materials that can be optimized to reduce losses and increase sensitivity, as well as by the long free‐space wavelengths associated with this spectral region. Here the exceptionally broad Reststrahlen bands of two Hf‐based transition metal dichalcogenides (TMDs) that can support surface phonon polaritons (SPhPs) within the mid‐infrared (mid‐IR) into the terahertz (THz) are reported. In this vein, the IR transmission and reflectance spectra of hafnium disulfide (HfS2) and hafnium diselenide (HfSe2) flakes are measured and their corresponding dielectric functions are extracted. These exceptionally broad Reststrahlen bands (HfS2: 165 cm−1; HfSe2: 95 cm−1) dramatically exceed that of the more commonly explored molybdenum‐ (Mo) and tungsten‐ (W) based TMDs (≈5–10 cm−1), which results from the over sevenfold increase in the Born effective charge of the Hf‐containing compounds. This work therefore identifies a class of materials for nanophotonic and sensing applications in the mid‐ to far‐IR, such as deeply sub‐diffractional hyperbolic and polaritonic optical antennas, as is predicted via electromagnetic simulations using the extracted dielectric function.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Sep 06, 2022
- Source ID
- 10.1002/adom.202200933
Entities
People
- Christopher J Ciccarino
- Dominik M Juraschek
- Georgios Varnavides
- J. Ryan Nolen
- Jack E. Allen
- Joshua D Caldwell
- Prineha Narang
- Ryan A. Kowalski
- Sebastian Miki-Silva
- Stephanie Law
Organizations
- City University of New York
- Gordon and Betty Moore Foundation
- Harvard University
- National Aeronautics and Space Administration
- National Science Foundation
- Office of Naval Research
- Tel Aviv University
- United States Department of Energy
- University of Delaware
- Vanderbilt University