Developing Parallel 3D FDTD Numerical Models for Studying Metal-Coated Periodic Nanostructures
Date Issued
2010
Date
2010
Author(s)
Chen, Yi-Hui
Abstract
In this thesis, a three dimensional (3D) finite-difference time-domain (FDTD) numerical model is developed with parallel codes and applied to study the near-field enhancement and the reflectance and transmittance spectra of two subwavelength periodic structures. The Drude-Lorentz model is implemented for a metallic dispersive material into the FDTD algorithm and the uniaxial perfectly matched layer (UPML) is employed as a absorber for truncating the computational domain. For the large computational time and memory in the 3D FDTD method, we make use of different parallel computation methods, which are the Open Multi-Processing (OpenMP), and the blocking and nonblocking message passing interface (MPI) libraries. The first structure studied is the AgFON substrate with silver film deposited over nanospheres, which is applied as a chemical or biological sensor by the surface-enhanced Raman scattering (SERS) mechanism. The optimal structural parameters of the AgFON substrate for SERS application can be identified as the wavelength of the reflectance minimum coincides with that of the given excitation. In that situation, the AgFON substrate possesses greater electric-field enhancement on the surface compared to others with different parameters. The second structure is the periodic antireflection subwavelength structure (ASS) deposited with a silver layer forming a thermal-insulation film. The reflectance and transmittance spectra under normally incident wave condition are calculated. The strong electric fields around the metal surface are found to correspond to a relatively large dip in the transmittance spectrum separating the spectral regions into two parts: high transmittance in the shorter wavelength region and low transmittance in the longer wavelength region. Through varying the structural parameters, including adjusting the wavelength of the dip to 700 nm and enhancing the transmittance ratio of the two parts in the spectrum, the better design for thermal-insulation application is obtained. The FDTD calculated results for both structures are compared with respective measurement results with good agreement observed.
Subjects
3D
FDTD
parallel
metal-coated
periodic structure
SERS
thermal-insulation film
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