The incorporation of responsive elements into photonic
crystals
is an effective strategy for fabricating active optical components
to be used as sensors, actuators, and modulators. In particular, the
combination of simple multilayered dielectric mirrors with optically
responsive plasmonic materials has proven to be successful. Recently,
Tamm plasmon (TP) modes have emerged as powerful tools for these purposes.
These modes arise at the interface between a distributed Bragg reflector
(DBR) and a plasmonic layer and can be excited at a normal incidence
angle. Although the TP field is located usually at the DBR/metal interface,
recent studies have demonstrated that nanoscale corrugation of the
metal layer permits access to the TP mode from outside, thus opening
exciting perspectives for many real-life applications. In this study,
we show that the TP resonance obtained by capping a DBR with a nanostructured
layer of silver is responsive toEscherichia coli. Our data indicate that the modification of the TP mode originates
from the well-known capability of silver to interact with bacteria,
within a process in which the release of Ag+ions leaves
an excess of negative charge in the metal lattice. Finally, we exploited
this effect to devise a case study in which we optically differentiated
between the presence of proliferative and nonproliferative bacteria
using the TP resonance as a read-out. These findings make these devices
promising all-optical probes for bacterial metabolic activity, including
their response to external stressors.