Ceramic-Based High-Q Retroreflectors for Sub-mm Localization in High-Temperature Environments

This scientific paper is an outcome of the MARIE project (for more information, see trrmarie.de) C09. This research addresses the development of innovative frequency-coded tags for localization, sensing, and ranging in harsh environments. The study focuses on enhancing orientation-insensitive THz retroreflectors through advanced approaches, including multi-notch high Radar Cross-Section (RCS) Corner Reflectors (CR) and Quasi Conformal Transformation Optics (QCTO)-enabled designs. Core innovations involve the integration of Luneburg lenses with Photonic Crystal (PhC)-based coding particles, fabricated using advanced materials such as Deep Reactive Ion Etched (DRIE) High-Resistive Silicon (HR-Si) and Lithography-based Ceramic Additive Manufacturing (LCM) with Alumina (Al₂O₃). These designs enable high-Q resonators for effective signal detection in extreme conditions up to 1200 °C, as in an indoor fire scenario. Achievements include wide-field-of-view (FoV) retroreflectors, frequency-coded lens reflectors, and wireless readouts capable of sub-mm localization. Future work will explore multi-material additive manufacturing and Liquid Crystal (LC)-based Reconfigurable Intelligent Surfaces (RIS) to advance state-of-the-art localization systems for autonomous rescue applications. These findings establish a foundation for robust, high-temperature sensor fusion technologies.