Authors:

Benjamin Wassgren

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About Paper:

Light propagates differently inside different materials. One special class is hyperbolic materials, named after their hyperbolic isofrequency surfaces in wavevector space. This quality allows for negative refraction or sub- wavelength information storage. One promising hyperbolic material is alpha-MoO3, a biaxial anisotropic material. These properties are rare, but make it uniquely capable in nanoscale radiative energy transport applications. The dielectric function is a fundamental property of hyperbolic materials, but has only been measured in alpha-MoO3 at room temperature. This paper measures the temperature dependence of alpha- MoO3's dielectric function in the infrared region. The Lorentz model, a building block of the dielectric function, is used with Fresnel's equations to generate a reflectivity spectrum. This spectrum is then compared to a spectrum measured using Fourier Transform Infrared Response (FTIR) spectroscopy, iterating unknown parameters until error is minimized. For a more accurate fitting, Raman spectroscopy is used to determine some unknowns in the Lorentz model prior to fitting. The dielectric functions of varying temperature are then used to determine temperature dependence. The dielectric function is both a crucial optical property and related to radiative heat transfer. An understanding of its temperature dependence is a crucial step towards alpha-MoO3's use in optical and heat transfer settings.

Source:

Purdue University / 2023

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No topics listed

Co-authors:

Benjamin Wassgren