Self-Assembled Nanostructured Photonic-Plasmonic Metasurfaces for High-Resolution Optical Thermometry

Sensing devices for environment, safety, healthcare, and optoelectronic applications require an accurate and noninvasive monitoring of their temperature, because its variations markedly affect the overall response of the device. Monitoring the optical response of temperature-sensitive integrated photonic elements, such as microresonators or microinterferometers, is an appealing solution in this context. However, achieving high-resolution optical thermometry with such elements is unpractical and costly as this requires lithography processing, highly monochromatic laser sources, complex light coupling strategies. Here, a photonic-plasmonic metasurface design that enables practical optical thermometry with a sub-10(-3) degrees C resolution is proposed. It is based on a self-assembled nanostructured material implemented with a lithography-free process. The optical response of the temperature-sensitive metasurface is probed using a white light source and by monitoring the optical phase in a standard reflectance configuration. This facile, yet powerful, sensing scheme stands on the effective response of the metasurface, which involves the hybridization of thin film interference and low-quality-factor plasmon resonances to enable a quasi-darkness response with a sharp spectral variation (jump) of the optical phase. Such jump is equivalent with a high-quality-factor resonator that yields a high sensor responsivity and thus enables high-resolution optical thermometry.