Wide Dynamic Range Thermometer Based on Luminescent Optical Cavities in Ga<sub>2</sub>O<sub>3</sub>:Cr Nanowires
Manuel Alonso‐Orts, Daniel Carrasco, J. San Juán, M.L. Nó, A. de Andrés, Emilio Nogales, Bianchi Méndez
Abstract
Abstract Remote temperature sensing at the micro‐ and nanoscale is key in fields such as photonics, electronics, energy, or biomedicine, with optical properties being one of the most used transducing mechanisms for such sensors. Ga 2 O 3 presents very high chemical and thermal stability, as well as high radiation resistance, becoming of great interest to be used under extreme conditions, for example, electrical and/or optical high‐power devices and harsh environments. In this work, a luminescent and interferometric thermometer is proposed based on Fabry–Perot (FP) optical microcavities built on Cr‐doped Ga 2 O 3 nanowires. It combines the optical features of the Cr 3+ ‐related luminescence, greatly sensitive to temperature, and spatial confinement of light, which results in strong FP resonances within the Cr 3+ broad band. While the chromium‐related R lines energy shifts are adequate for low‐temperature sensing, FP resonances extend the sensing range to high temperatures with excellent sensitivity. This thermometry system achieves micron‐range spatial resolution, temperature precision of around 1 K, and a wide operational range, demonstrating to work at least in the 150–550 K temperature range. Besides, the temperature‐dependent anisotropic refractive index and thermo‐optic coefficient of this oxide have been further characterized by comparison to experimental, analytical, and finite‐difference time‐domain simulation results.