Harsh-environment sensors are key elements for the development of smart sensor networks. They enable extending the boundaries of such networks to the most inaccessible parts of human infrastructures. For the same reason, the design of harsh-environment sensors poses multiple material challenges, since these devices must survive in a hostile environment, while at the same time facilitate data acquisition and readout. Therefore, taking advantage of all the properties offered by a given material platform is crucial for the design of harsh-environment sensors.

In this regard, silicon carbide (SiC) is a semiconductor with excellent electrical, mechanical, thermal and chemical properties, which has already proven successful in the design of harsh-environment sensors. SiC also exhibits interesting optical properties. However, these have been disregarded in the design of sensor systems. Specifically, SiC is a polar dielectric with a highlyreflective band at mid-infrared (MIR) frequencies, supporting the excitation of surface phonon polaritons. It is also the lowest-loss epsilon-near-zero (ENZ) media known to date (i.e., a medium with a near-zero permittivity).

During the last years, we have introduced a number of theoretical breakthroughs demonstrating that ENZ media lead to a qualitatively different optical regime, where even a concept as basic as the geometry can play a qualitatively different role. Examples of this anomalous behaviour include: (i) Geometry-invariant resonators whose resonant frequency is independent of the geometry of their external boundary, (ii) particles immersed in ENZ do not obey conventional effective medium theories, but they behave as photonic dopants, (iii) the spatial coherence of thermal fields is intrinsically enhanced in ENZ media, independently of its geometry.

In this project, we will harness the unique properties of SiC at MIR frequencies, including its ENZ response, in order to develop a MIR interface with harsh-environment sensors. To this end, we will advance our previous theoretical breakthroughs to the stage of proof-of-concept prototypes, demonstrating the aforementioned optical effects in SiC microstructures. We expect that this MIR-interface will provide multiple functionalities of interest for harsh-environment sensors, including heat-management, actuation, multi-spectral sensing, optical readout, and control of Casimir and van der Waals forces.

In doing so, we will exploit material properties of SiC that have not been considered before for the design of sensor systems. Moreover, we will do so by exploring the unique optical regime observed in ENZ media. Therefore, our prototypes will bring multiple innovation opportunities for the design of harsh-environment sensors. Ultimately, these devices will find applications in
energy, aerospace, automotive, and communication market sectors.