Inter-Cavity Coupling Strength Control in Metal/Insulator Multilayers for Hydrogen Sensing

Abstract

Hydrogen (H2) sensing is crucial for modern energy storage technology, which looks to hydrogen as the most promising alternative to fossil fuels. In this respect, magnesium (Mg) offers unique possibilities, since magnesium and hydrogen easily undergo a reversible hydrogenation reaction where Mg reversibly converts into MgH2. From an optical point of view, this process produces an abrupt refractive index change, which can be exploited for sensing applications. To maximize this opportunity, we envision an architecture composed of two Ag/ITO/Mg metal/dielectric resonators facing each other and displaced by 200 nm of vacuum. This structure forms a so-called Epsilon-Near-Zero (ENZ) multi-cavity resonator, in which the two internal Mg layers, used as tunneling coupling metals, are accessible to environmental agents. We demonstrate that the hydrogenation of the two Mg layers leads to substantial changes in the strong coupling between the cavities composing the entire resonator, with a consequent abrupt modification of the spectral response, thus enabling the sensing mechanism. One of the main advantages of the proposed system with respect to previous research is that the proposed multilayered architecture avoids the need for lithographic processes. This feature makes the proposed architecture inexpensive and wafer-to-chip scalable, considering that each kind of substrate from common glass to silicon can be used. Therefore, our sensing architecture offers great promise for applications in embedded H2 sensors.

Surface-Enhanced Raman Spectroscopy on an As-deposited Fano Resonance Multilayer Substrate

“…17,18 In all the above cases, a liquid analyte is in contact with a substrate enriched with metals such as gold, silver, and copper 3 for obtaining Vis-SERS and aluminum for UV-SERS. 19 On the other hand, thin film multilayer systems can represent a very interesting alternative owing to their outstanding effects 20 such as electromagnetic mode confinement, plasmonic effect, self-collimation, and sharp resonances that found application in several fields as sensing, 21−23 structural color, 24,25 anticounterfeiting, 26−28 and cooling 29,30 to name a few.…”

“…On the other hand, thin film multilayer systems can represent a very interesting alternative owing to their outstanding effects such as electromagnetic mode confinement, plasmonic effect, self-collimation, and sharp resonances that found application in several fields as sensing, − structural color, , anticounterfeiting, − and cooling , to name a few.…”