posted on 2024-02-23, 22:14authored byHuong
Nguyen Que Tran, Khoa Nhu Tran, Satyathiran Gunenthiran, Juan Wang, Cheryl Suwen Law, Siew Yee Lim, Yong Cheow Gary Lim, Andrew D. Abell, Lluis F. Marsal, Abel Santos
The
fields of plasmonics and photonic crystals (PCs) have been
combined to generate model light-confining Tamm plasmon (TMM) cavities.
This approach effectively overcomes the intrinsic limit of diffraction
faced by dielectric cavities and mitigates losses associated with
the inherent properties of plasmonic materials. In this study, nanoporous
anodic alumina PCs, produced by two-step sinusoidal pulse anodization,
are used as a model dielectric platform to establish the methodology
for tailoring light confinement through TMM resonances. These model
dielectric mirrors feature highly organized nanopores and narrow bandwidth
photonic stopbands (PSBs) across different positions of the spectrum.
Different types of metallic films (gold, silver, and aluminum) were
coated on the top of these model dielectric mirrors. By structuring
the features of the plasmonic and photonic components of these hybrid
structures, the characteristics of TMM resonances were studied to
elucidate effective approaches to optimize the light-confining capability
of this hybrid TMM model system. Our findings indicate that the coupling
of photonic and plasmonic modes is maximized when the PSB of the model
dielectric mirror is broad and located within the midvisible region.
It was also found that thicker metal films enhance the quality of
the confined light. Gas sensing experiments were performed on optimized
TMM systems, and their sensitivity was assessed in real time to demonstrate
their applicability. Ag films provide superior performance in achieving
the highest sensitivity (S = 0.038 ± 0.001 nm
ppm–1) based on specific binding interactions between
thiol-containing molecules and metal films.