A Simulation Study for Field Enhancement due to Multiresonant Localized Surface Plasmon Excitation in the truncated Octa
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A Simulation Study for Field Enhancement due to Multiresonant Localized Surface Plasmon Excitation in the truncated Octahedral Gold Nanoparticle Arrays Sung Woo Choi, Min Woo Oh and Doo Jae Park
∗
School of Nano Convergence Technology, Hallym University, Chuncheon 24252, Korea
Sungho Park Department of Chemistry, Sungkyunkwan University, Suwon 16419, Korea (Received 6 October 2020; revised 16 October 2020; accepted 18 October 2020) We theoretically demonstrates large field enhancement at the close-packed, truncated octahedral gold nanoparticle array by using a finite difference time domain method. A multiple peak at the visible and near infrared frequency implies the multiple resonance in the nanostructures, corresponding to the dipolar and quadrupolar mode excitation of electric field at the single octahedral particles. The splitting of two adjacent resonant peak as a function of the distance of the particles implies the existence of the significant coupling between the resonant modes of the individual nanoparticles. The electric field profile at the gap between the particles shows the field enhancement due to such mode couplings, where dipolar and quadrupolar mode are simultaneously involved. Such evolution of mode coupling with increasing gap distance confirms the resonant modes excitation and their coupling is the origin of the strong field enhancement. Simulation with different polarization of the incident light denotes the dominant coupling mode is governed by the size of the interaction area. Importantly, electric field at the gap is hugely enhanced up to 17 at the optimal gap distance of 4 nm. Keywords: Field enhancement, Nanoparitcles, Localized Surface Plasmon DOI: 10.3938/jkps.77.1148
I. INTRODUCTION An enhancement of electromagnetic field has been a main topic in nanoscale optics and related phenomena, because of its enormous potentials for various applications such as high sensitive molecular detection [1–3], imaging with ultrahigh spatial resolution [4–9], and ultrafast strong field emissions [10–13]. Specifically, increase of the effective cross section between light and matter due to field enhancement enabled the attomolar detection and characterization of molecules by means of the surface-Enhanced Raman Spectroscopy (SERS) recently [14–16]. In these researches, the assembly of closely packed, periodic arrays of single metallic nanoparticles was proven to be a key in generating hotspot with high controllability, where enormous increase of Raman scattering cross section was manifested. Generally, the hotspot in metallic nanoparticle arrays are formed in the gap between adjacent nanoparticles due to the mutual induction of additional charges at both face of the gap [17]. In addition, normal mode excitation ∗ E-mail:
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pISSN:0374-4884/eISSN:1976-8524
of individual nanoparticle which is governed by the size and shape of the particle also contributes in the enhancement of the local electric field. Hence, the hotspot formation mechanism of nanoparticle arrays involves normal mode excitation and i
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