Open AccessSurface-enhanced terahertz spectroscopy using gold rod structures resonant with terahertz waves
Author(s) -
Kosei Ueno,
Sho Nozawa,
Hiroaki Misawa
Publication year - 2015
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.23.028584
Subject(s) - terahertz radiation , materials science , terahertz spectroscopy and technology , plasmon , spectroscopy , surface plasmon , surface plasmon resonance , localized surface plasmon , optoelectronics , optics , surface plasmon polariton , infrared spectroscopy , chemistry , nanotechnology , physics , nanoparticle , organic chemistry , quantum mechanics
Terahertz (THz) spectroscopy is a promising method to measure the spectrum of low-frequency modes of molecules or ensembles, such as crystals and polymers, including proteins. However, the main drawback of THz spectroscopy is its extremely low sensitivity. In the present study, we report on signal enhancement in THz spectroscopy achieved by depositing amino acid molecules or their derivatives on a gold rod structured silicon substrate whose localized surface plasmon resonance is exhibited in the THz frequency region. The distinct peaks derived from the enhancement of the inherent spectrum based on a molecular crystal were clearly observed when a longitudinal plasmon resonance mode of the gold rod structure was excited and the plasmon resonance band overlapped the molecular/intermolecular vibrational mode. We discuss the mechanism by which surface-enhanced THz spectroscopy was induced from the viewpoint of the enhancement of light-matter coupling due to plasmon excitation and the modulation of the plasmon band by dipole coupling between the plasmon dipole and molecular/intermolecular vibrational modes.