scholarly journals Size Determination of Polystyrene Sub-Microspheres Using Transmission Spectroscopy

2020 ◽  
Vol 10 (15) ◽  
pp. 5232
Author(s):  
Tien Van Nguyen ◽  
Linh The Pham ◽  
Khuyen Xuan Bui ◽  
Lien Ha Thi Nghiem ◽  
Nghia Trong Nguyen ◽  
...  
Keyword(s):  
Time Domain ◽  
Finite Difference Time Domain ◽  
Fdtd Simulation ◽  
Transmission Spectra ◽  
Experimental Transmission ◽  
Straightforward Method ◽  
Quartz Substrates ◽  
Difference Time ◽  
Good Agreement

Nano/micro polystyrene (PS) beads have found many applications in different fields spanning from drug delivery, bio-diagnostics, and hybrid plasmonics to advanced photonics. The sizes of the PS beads are an important parameter, especially in plasmonic and photonic experiments. In this work, we demonstrate a quick and straightforward method to estimate the diameters of sub-microspheres (0.2 μm to 0.8 μm) using the transmission spectra of a close-packed monolayer of polystyrene beads on glass or quartz substrates. Experimental transmission spectra of the PS monolayers were verified against finite-difference time-domain (FDTD) simulation and showed good agreement. The effects of the substrates on the transmission spectra and, hence, the accuracy of the method were also studied by simulation, which showed that common transparent substrates only cause minor deviation of the PS bead sizes calculated by the proposed method.

scholarly journals Metasurface of Combined Semicircular Rings with Orthogonal Slit Pairs for Generation of Dual Vector Beams

Nanomaterials ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1718
Author(s):  
Qian Kong ◽  
Manna Gu ◽  
Xiangyu Zeng ◽  
Rui Sun ◽  
Yuqin Zhang ◽  
...  
Keyword(s):  
Time Domain ◽  
Finite Difference Time Domain ◽  
Polarized Light ◽  
Orientation Angle ◽  
Fdtd Simulation ◽  
Dual Vector ◽  
Vector Beams ◽  
Linearly Polarized ◽  
Potential Applications ◽  
Difference Time

Manipulation of multichannel vector beams (VBs) with metasurfaces is an important topic and holds potential applications in information technology. In this paper, we propose a novel metasurface for the generation of dual VBs, which is composed of orthogonal slit pairs arranged on multiple groups of combined semicircular rings (CSRs). A group of CSRs include a right-shifted set and a left-shifted set of semicircular rings, and each set of semicircular rings has two halves of circles with different radii, sharing the same shifted center. Under the illumination of linearly polarized light, the two shifted sets of semicircular rings generate the two VBs at the shifted center positions on the observation plane. The slit units of each set are designed with independent rotation order and initial orientation angle. By adjusting the linear polarization of illumination, both two VBs with their orders and polarization states are independently controlled simultaneously. The principle and design are demonstrated by the finite-difference time domain (FDTD) simulation. The work is of significance for miniatured devices of VB generators and for related applications.

Focusing Technique for Holographic Subsurface Radar Based on Image Entropy

2021 ◽  
Vol 36 (4) ◽  
pp. 373-378
Author(s):  
Haewon Jung ◽  
Dal-Jae Yun ◽  
Hoon Kang
Keyword(s):  
Numerical Simulation ◽  
Time Domain ◽  
Finite Difference Time Domain ◽  
Software Package ◽  
Reconstruction Algorithm ◽  
Simulation Software ◽  
Material Information ◽  
Difference Time ◽  
Actual Depth ◽  
Good Agreement

An image focusing method for holographic subsurface radar (HSR) is proposed herein. HSR is increasingly being utilized to survey objects buried at shallow depths and the acquired signals are converted into an image by a reconstruction algorithm. However, that algorithm requires actual depth and material information or depends on human decisions. In this paper, an entropy-based image focusing technique is proposed and validated by numerical simulation software package based on finite-difference time-domain method and experiment. The resulting images show good agreement with the actual positions and shapes of the targets.

Quantifying Sub-gridding Errors in Standard and Hybrid Higher Order 2D FDTD Simulations

2021 ◽  
Vol 35 (11) ◽  
pp. 1428-1429
Author(s):  
Madison Le ◽  
Mohammed Hadi ◽  
Atef Elsherbeni
Keyword(s):  
Finite Difference ◽  
Time Domain ◽  
Finite Difference Time Domain ◽  
Contrast Ratio ◽  
Higher Order ◽  
Fdtd Simulation ◽  
Fdtd Simulations ◽  
2D Fdtd ◽  
Difference Time

Sub-gridding errors for a 2D Finite-Difference Time-Domain (FDTD) simulation are compared for both the standard FDTD and Hybrid higher order FDTD cases. Subgridding contrast ratios of 1:3, 1:9, 1:15, and 1:27 are considered and analyzed. A correlation is seen between the increase of contrast ratio with the increase of sub-gridding errors for both standard and hybrid cases. However, a trend of errors reduction when using hybrid formulations over standard formulations is apparent for each contrast ratio.

Time-domain analysis of a CRLH coupled-line coupler using the CN-FDTD method

2018 ◽  
Vol 11 (1) ◽  
pp. 94-103 ◽  
Author(s):  
Mahdieh Gholami Mayani ◽  
Shahrooz Asadi ◽  
Shokrollah Karimian
Keyword(s):  
Time Domain ◽  
Finite Difference Time Domain ◽  
Fdtd Method ◽  
Time Domain Analysis ◽  
Step Size ◽  
Dramatic Decrease ◽  
Coupled Line ◽  
Left Handed ◽  
Difference Time ◽  
Good Agreement

In this study, the implicit Crank–Nicolson finite-difference time-domain (CN-FDTD) method is applied to discretize the governing telegrapher's equations of a composite right-/left-handed (CRLH) coupled-line coupler. The unconditionally stable CN-FDTD is compared with the conventional leap-frog (LF) FDTD method. The results obtained from the CN-FDTD scheme show up to 10 times increase in the temporal step size, reflecting in a dramatic decrease in processing time; in addition to having a good agreement with the LF method and the measurements.

Field Distribution Adjacent to Apertures Located on Infinite Plates

2014 ◽  
Vol 602-605 ◽  
pp. 335-338
Author(s):  
Run Xiong ◽  
Bin Chen ◽  
Zheng Jun Wang
Keyword(s):  
Electromagnetic Field ◽  
Field Distribution ◽  
Time Domain ◽  
Finite Difference Time Domain ◽  
Infinite Plate ◽  
Fdtd Simulation ◽  
Electromagnetic Field Distribution ◽  
Coupling Principle ◽  
Difference Time ◽  
Electromagnetic Field Component

In this paper, electromagnetic field distribution adjacent to the aperture is analyzed to help deducing the coupling principle of apertures. The aperture is located on an infinite plate to avoid the effect of other structures. Taking advantage of high-resolution standard finite-difference time-domain (FDTD) simulation, it is possible to observe the electromagnetic field distribution adjacent to the aperture. From analyses, it can be seen that the electromagnetic field component is dramatically varied adjacent to the aperture, and conclusions drawn here is helpful to deduce the coupling principle of apertures.

scholarly journals Investigating the Fabrication Imperfections of Plasmonic Nanohole Arrays and Its Effect on the Optical Transmission Spectra

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Amr M. Mahros ◽  
Marwa M. Tharwat
Keyword(s):  
Time Domain ◽  
Finite Difference Time Domain ◽  
Optical Transmission ◽  
Fdtd Method ◽  
Extraordinary Optical Transmission ◽  
Gold Films ◽  
Transmission Spectra ◽  
Nanohole Arrays ◽  
Optical Transmission Spectra ◽  
Difference Time

We investigate the extraordinary optical transmission spectra of thin gold films perforated with imperfect nanohole arrays using the finite difference time domain (FDTD) method. Exponential shapes for the nanohole sidewalls are used. To the best of our knowledge, such investigation of transmission spectra of imperfect nanohole arrays has not previously been demonstrated. It was found that the asymmetry between the two openings of the circular nanoholes or bending to their sidewalls strongly modifies both the intensity and resonance positions of the transmission spectra. Furthermore, the results of this study assist in explaining the technicality of extraordinary optical transmission phenomenon and why some experimental results on transmission differ from those expected.

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