Investigation of dual-narrowband plasmonic perfect absorbers at visible frequencies for biosensing
Author
Ali, Farhan
Advisor
Gülseren, Oğuz
Date
2019-12Publisher
Bilkent University
Language
English
Type
ThesisItem Usage Stats
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Abstract
Since the introduction of first plasmonic perfect absorber (PA) in early 2008 by
Landy et al., numerous studies have demonstrated their superior optical performance
in frequencies ranging from terahertz to visible region of electromagnetic
spectrum. In the literature broadband PAs are studied in more detail compared
to narrowband PAs as their large absorption bandwidths make them a prime
candidate for energy harvesting applications or security and defense. Recently
scientists have shown a great interest in designing narrowband PAs by controlling
the optical losses of the plasmonic materials as the narrowband resonances with
a high quality-factor is particularly important for label-free biosensing. However,
given the lossy optical properties of metals, this task has been challenging and
requires delicate investigation and parameter control in contrast to broadband
perfect absorbers.
In this research, we numerically studied and experimentally fabricated a
narrow-band plasmonic perfect absorber based on a metal-insulator-metal con-
figuration. We analyzed the origin of perfect absorption for our proposed system
and investigated the parameters that effect the optical properties. The purposed
plasmonic structure comes up with a dual narrow-band absorption peaks at visible
and near-infrared region of electromagnetic spectrum with near unity absorption
e ciency. The physical origin of these absorption peaks is shown to be the excitation
of propagating and localized surface plasmon resonances at certain individual
frequencies, that leads to impedance matching and critical coupling when certain
conditions are satisfied. Finally, we analyzed the sensing capabilities of PA by embedding nanostructure
into different background refractive index, resulting in sensitivity of 500 nm/RIU,
making such a platform suitable for biosensing and spectroscopic applications. This work analyzes the perfect absorption phenomena in visible frequencies in
detail and will be a go to guide for researchers in the perfect absorber community.
Keywords
Plasmonic nanostructuresMetamaterial
MIM perfect absorber
Narrowband perfect absorbers
Biosensing