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    Finite-difference time-domain study of Si nanorod arrays with UV and green light
    (Korean Physical Soc, 2022) Keles, Filiz; Seo, Hye-Won
    The finite-difference time-domain (FDTD) simulation on the absorption properties of Si nanorods with different spacings at UV and green light has been conducted. It was revealed that the enhanced absorption along the sidewalls of Si nanorods occurred, parallel to the light polarization directions, at UV-light while the green light is literally confined towards the nanorod center which leads to the V-shape absorption. The significant difference in absorption profile at two different illuminations is mainly due to the distinct origin of the light-matter interactions. For the UV light, the polarization induced local electric field in the gap between nanorods is responsible for the results observed. However, the confined prolonged absorption of the green light is attributed to the non-negligible total internal reflection inside Si nanorod waveguide.
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    Investigation of Enhanced Light Absorption in GaN Nanorod Arrays by Finite-Difference Time-Domain Method
    (Korean Vacuum Society, 2022) Keles, Filiz; Kim, Il-Hwan; Seo, Hye-Won
    Finite-difference time-domain simulation of GaN nanorod arrays with linearly polarized ultraviolet (UV) (325 nm) and visible (513 nm) light has been carried out. Enhanced light absorption of nanorods with confined electric field in the surrounding gap was observed. To identify the rationale of this finding, we studied their three-dimensional graphical profile and then realized that 1) modal resonance is developed with absorption gain in the UV region and 2) reflection at the interface with substrate leads to a subtle increase of absorption of visible light. By solving the eigenvalue equation, we also confirmed that TM11 mode of leaky-mode resonance is responsible for the observed modal absorption of UV light. © 2022, Korean Vacuum Society. All rights reserved.
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    Modulated 3D light absorption profile in GaN nanorod arrays
    (Elsevier, 2021) Keles, Filiz; Seo, Hye-Won
    The depth dependent UV-light absorption profile of GaN nanorods with different lattice arrays and filling factors was studied using finite-difference time-domain (FDTD) methods. By comparing to the results from LambertBeer's law with Maxwell-Garnett effective medium theory, we identified the quantitative contribution from nano-scattering effect on the light absorption in the nanorod arrays. The FDTD study of graphical 3D profile of light absorption and electric field intensity was parallelly conducted to investigate the origin of the nano scattering. We found that the coupled electric field in the gap regions led to the larger absorption crosssection of the nanorod arrays, which is attributed to the distorted depth profile of the light absorption.