Advances in sensors using lossy mode resonances

Lossy mode resonance (LMR) is a phenomenon that is observed in the optical spectrum when a mode that progresses through a waveguide starts to be guided in a thin film deposited on this waveguide under certain conditions, mainly related to materials and angles of incidence. An important property that LMRs have is that they can be guided into the thin film with both magnetic (TM) and electrical (TE) polarized light, unlike the other two main types of optical resonances with the same modus operandi that complete this trilogy, surface plasmon resonances (SPRs) and surface exciton plasmon resonances (SEPR). Regarding the potential materials that make up thin films, they include dielectrics suchs as metal oxides such as titanium dioxide (TiO2), zinc oxide (ZnO), tin oxide (SnO2) or polymers. In all cases it must be fulfilled that the real part of the refractive index must be greater than its imaginary part, unlike also the SPR and SEPR. As for the angles of incidence, they must be close to 90º, which explains the success of deposition of thin films around an optical fiber to obtain sensors based on LMR, although interesting results have recently been obtained using planar waveguides. This work will present the main milestones obtained during more than a decade using LMR-based sensors for the detection of multiple parameters. Among these interesting aspects, we can mention the sensitivity records achieved, hybridization with other sensing technologies or the possibility of multiplexing multiple sensors on the same substrate, just to mention a few.