Mie Voids for High-Pressure Refractive Index Sensing

A simpler and more sensitive method for the measurement of the refractive index (RI) of materials under high pressure is desirable for the advancement of materials science. Nanophotonic RI sensing based on the localized surface plasmon resonance (LSPR) of gold nanorods dispersed in an anvil cell could achieve simplicity and high sensitivity. However, this method is restricted by deformations of the nanorods resulting from nonhydrostatic effects and so on. Here, we have developed a dielectric Mie-void resonator array for local RI sensing at high pressures by fabricating a submicron hole array on an anvil of stiff 4H-silicon carbide. The spectral shift of the Mie voids allowed us to detect pressure-induced changes in the RI of water with the sensitivity of approximately 290 ± 110 nm per RI unit, which is comparable with that based on LSPR. Our method has the advantages of robustness against deformation and a fine spatial resolution.