Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

# Bragg Mirrors for Thermal Waves

Version 1 : Received: 9 October 2021 / Approved: 12 October 2021 / Online: 12 October 2021 (10:21:55 CEST)

How to cite: Camacho de la Rosa, A.; Becerril, D.; Gómez-Farfán, G.; Esquivel-Sirvent, R.P. Bragg Mirrors for Thermal Waves. Preprints 2021, 2021100174 (doi: 10.20944/preprints202110.0174.v1). Camacho de la Rosa, A.; Becerril, D.; Gómez-Farfán, G.; Esquivel-Sirvent, R.P. Bragg Mirrors for Thermal Waves. Preprints 2021, 2021100174 (doi: 10.20944/preprints202110.0174.v1).

## Abstract

We present a numerical calculation of the heat transport in a Bragg mirror configuration made of materials that do not obey Fourier's law of heat conduction. The Bragg mirror is made of materials that are described by the Cattaneo-Vernotte equation. By analyzing the Cattaneo-Vernotte equation's solutions, we define the thermal wave surface impedance to design highly reflective thermal Bragg mirrors. Even for mirrors with a few layers, very high reflectance is achieved ($>90\%$). The Bragg mirror configuration is also a system that makes evident the wave-like nature of the solution of the Cattaneo-Vernotte equation by showing frequency pass-bands that are absent if the materials obey the usual Fourier's law.

## Keywords

Cattaneo-Vernotte; waves; Bragg

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