Figure 1. (a) 3D model of a MIM WG structure, which constitutes a thin
metal film deposited on a substrate. And a narrow slit (few nm) is
inscribed in the thin-film which provides a way for the SPP to propagate
in a low-index medium, (b) a cross-sectional view of the E-field
distribution taken at the output of the MIM WG, (c) The relationship
between the real part of the effective index and the ambient refractive
index.
In this mini-review, the recent advances in MIM WG-based plasmonic
sensors are investigated and trying to figure out the possible causes
which limit the experimental demonstration of such attractive devices.
To the best of the author’s knowledge, almost all the reports are
devoted to the numerical analysis of the nanoscale sensing devices
without addressing the real challenges that can arise during
nanofabrication, sensing mechanisms (by using microfluidic channels),
and optical characterization. There are more than ~6000
reports published up till now on MIM WG devices indexed in the Scopus
database. Butt et al. have also published more than 30 papers on the
numerical study of the MIM WG-based plasmonic sensors. Most of the MIM
WG-based sensors are based on unique resonant cavity schemes (as
discussed later) where the gap between the bus WG and the cavity is
~10 nm-50 nm, furthermore, the additional geometric
parameters such as the width of the bus WG, defects or baffles are also
in nm scale. This raises a question on the method of fabrication,
reproducibility, and light coupling methods during device
characterization.