Surface vs. bulk sensitivity of sensors based on Rayleigh anomalies in metallic nanogratings

Abstract

This work provides numerical and experimental evidence that a significant difference exists between bulk and surface sensitivities in nanodevices based on Rayleigh anomalies (RAs) when employed for sensing the surrounding refractive index. In particular, recently proposed sensing schemes based on RAs in optical nanogratings are shown to be applicable only in the presence of bulk analytes. In the presence of thin overlays of analytes, instead, the (surface) sensitivity deteriorates up to two orders of magnitude by comparison with its bulk value, as well as with typical surface sensitivities exhibited by sensors based on surface plasmon resonances. This aspect is of fundamental importance as it severely limits the practical applicability of these devices to chemical and label-free biological sensing.

Biological sensing using hybridization phase of plasmonic resonances with photonic lattice modes in arrays of gold nanoantennas

“…In fact in this regime FoM is ∼9 while in the LPSR dominant regime it is ∼3.5. These findings have been previously highlighted by previous reports [20,22,23]. Our results in figure 4(a), however, show the conditions wherein hybridization of LSPR and RA provides optimal sensitivities.…”

“…A lot of research has compared the merits of LSPR and SLRs with each other. Previous investigations on sensors based on SLRs have shown improved figure of merit (FoM) [14,20,21], high bulk refractive index (RI) sensitivity [18,19,22,23], and enhanced phase sensitivity [19], compared to solely LSPR based sensors.…”