Liberal Olleta, Íñigo

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https://academica-e.unavarra.es/handle/2454/49405

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Liberal Olleta

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Íñigo

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Ingeniería Eléctrica, Electrónica y de Comunicación

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ISC. Institute of Smart Cities

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0000-0003-1798-8513

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88733

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9467

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2022 - 20242
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Author: Pérez Escudero, José Manuel × Subject: Silicon carbide ×

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    PublicationOpen Access
    Exploring surface roughness in epsilon-near-zero materials
    (IEEE, 2024-10-08) Navajas Hernández, David; Pérez Escudero, José Manuel; Liberal Olleta, Íñigo; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza; Institute of Smart Cities - ISC
    The practical application of materials with epsilon-near-zero (ENZ) characteristics heavily depends on the quality of real-world ENZ materials, considering factors like material losses and surface roughness. These materials have drawn interest due to their strong nonlinear responses and unique behavior. In this study, an experimental examination of how surface roughness affects ENZ substrates is presented. We employed silicon carbide (SiC) substrates deliberately engineered to exhibit different levels of roughness, enabling us to analyze samples spanning from a few to hundreds of nanometers in size scales. Substrates with nanoscale roughness experience adverse effects due to longitudinal phonon coupling and strong ENZ fields, while at larger roughness scales, the ENZ band demonstrates to be more robust compared to dielectric and surface phonon polariton (SPhP) bands.
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    PublicationOpen Access
    Narrowband and spectrally robust thermal emission from metallic thin films on top of epsilon-near-zero substrates
    (IEEE, 2022) Navajas Hernández, David; Pérez Escudero, José Manuel; Liberal Olleta, Íñigo; Ingeniería Eléctrica, Electrónica y de Comunicación; Institute of Smart Cities - ISC; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
    The absorption and emission of infrared radiation by ultra-thin metallic films is a key element in several thermal engineering applications such as heat and energy management, and thermal camouflage. However, ultra-thin metallic films are broadband and low-efficiency emitters. Here, we demonstrate numerically and experimentally that metallic films placed on top of epsilon-near-zero (ENZ) substrates become narrowband and efficient thermal emitters. Our experiments show that ENZ-based emitters feature a narrow linewidth whose frequency positioning is robust against variations in the geometry of the system and the observation angle. Moreover, since ENZ emitters are based on the material properties of the substrate, no nanofabrication processes are needed, opening the pathway towards widefield and large-scale applications.