By taking a graphene nanoribbon as a resonator, we have numerically and analytically investigated the spectral characteristics of plasmon-induced transparency in integrated graphene waveguides. For the indirect coupling, the formation and evolution of the transparency window are determined by the excitation of the super resonances, as well as by the destructive interference and the coupling strength between the two resonators, respectively, while for the indirect coupling, the peak transmission and corresponding quality factor can be dynamically tuned by adjusting the Fermi energy of graphene nanoribbons and the transparency peak shifts periodicity with the round-trip phase accumulated in the graphene waveguide region. Analytical results based on temporal coupled mode theory (CMT) show good consistence with the numerical calculations. Our findings may support the design of ultra-compact plasmonic devices for optical modulating.
Pushing
the detection limit of infrared absorption (IR) through
surface-enhanced (SEIRA) approaches have far-reaching prospect for
related applications in molecular analysis and detection. Specifically
engineered Au nanowires (NWs) can be applied as the surface-enhancing
substrates in colloidal solution, given their longitudinal surface
plasmon resonance (SPR) being aspect-ratio dependent and extendable
into the infrared region. Through carefully designed control experiments,
we realized resonant coupling between the longitudinal surface plasmons
of Au NWs and the vibration modes of the bonded oleylamine (OA) ligands.
In our system, after deliberately tuning thickness of the OA ligands
and ratio of the detached/attached ligands in the solution, the apparent
enhancement factor of IR signal from ligands around Au NWs could be
pushed up to 5.29 × 104. Given the facile tuning of
SPR properties of Au NWs in the colloidal solution and the performance
demonstrated in the report, our work could be an intriguing platform
for SEIRA implementations in a broad spectrum of circumstances.
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