Chromium doped gallium oxide nanowire-based thermometer and the study of the anisotropic refractive index temperature dependence

Daniel Carrasco; Manuel Alonso-Orts; Eva Nieto; Rosalía Serna; José María San Juan; María Luisa Nó; Jani Jesenovec; John McCloy; Alicia de Andrés; Emilio Nogales Díaz; Bianchi Méndez

doi:10.1117/12.3012105

15 March 2024 Chromium doped gallium oxide nanowire-based thermometer and the study of the anisotropic refractive index temperature dependence

Daniel Carrasco, Manuel Alonso-Orts, Eva Nieto, Rosalía Serna, José María San Juan, María Luisa Nó, Jani Jesenovec, John McCloy, Alicia de Andrés, Emilio Nogales Díaz, Bianchi Méndez

Author Affiliations +

Proceedings Volume 12887, Oxide-based Materials and Devices XV; 128870A (2024) https://doi.org/10.1117/12.3012105
Event: SPIE OPTO, 2024, San Francisco, California, United States

Abstract

Gallium oxide is being widely studied, mainly for high-power electronics applications. It is a very promising material for photonic/optoelectronic applications, such as solar-blind UV detectors and light emitters. In this work, we study the temperature-dependent behavior of the optical properties of microcavities based on luminescent β-Ga₂O3:Cr nanowires that emit an intense red-infrared band. Two distributed Bragg reflectors (DBR), when milled with a focused ion beam (FIB) and separated some microns, result in an optical microcavity that confines the light longitudinally. Both chromium R lines and Fabry-Perot spectral resonances (FPSR) are observed to shift as temperature varies, making these DBRs a valuable thermometer in a wide temperature range, due to both luminescent and interferometric transducing mechanisms. The underlying origin of this shift, in the case of the FPSR, is mainly the variation of the refractive index with temperature and the thermal expansion of the cavity. Ellipsometry studies carried out at different temperatures in bulk β-Ga₂O₃ yielded the dispersion relations for the three main crystal axes, i.e. its temperature-dependent anisotropic refractive index. These results were implemented in finite-difference time-domain (FDTD) simulations to compare the expected spectral shift of the FPSR in the modelled system with the experimental shift in the DBR cavities, as obtained experimentally by micro-photoluminescence. The results from these two approximations, and a third one based on solving the relevant analytical equations, are compared.

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Daniel Carrasco, Manuel Alonso-Orts, Eva Nieto, Rosalía Serna, José María San Juan, María Luisa Nó, Jani Jesenovec, John McCloy, Alicia de Andrés, Emilio Nogales Díaz, and Bianchi Méndez "Chromium doped gallium oxide nanowire-based thermometer and the study of the anisotropic refractive index temperature dependence", Proc. SPIE 12887, Oxide-based Materials and Devices XV, 128870A (15 March 2024); https://doi.org/10.1117/12.3012105

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