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Diao Y, Liu L, Deng N, Lyu S, Hirata A. Tensor-conductance model for reducing the computational artifact in target tissue for low-frequency dosimetry. Phys Med Biol 2023; 68:205014. [PMID: 37722382 DOI: 10.1088/1361-6560/acfae0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Accepted: 09/18/2023] [Indexed: 09/20/2023]
Abstract
Objective.In protecting human from low-frequency (<100 kHz) exposure, an induced electric field strength is used as a physical quantity for assessment. However, the computational assessment suffers from a staircasing error because of the approximation of curved boundary discretized with cubic voxels. The international guidelines consider an additional reduction factor of 3 when setting the limit of external field strength computed from the permissible induced electric field. Here, a new method was proposed to reduce the staircasing error considering the tensor conductance in human modeling for low-frequency dosimetry.Approach.We proposed a tensor-based conductance model, which was developed on the basis of the filling ratio and the direction of the tissue interface to satisfy the electric field boundary condition and reduce staircasing errors in the target tissue of a voxel human model.Main results.The proposed model was validated using two-layer nonconcentric cylindrical and spherical models with different conductivity contrasts. A comparison of induced electric field strengths with solutions obtained using an analytical formula and finite element method simulation indicated that for a wide range of conductivity ratios, staircasing errors were reduced compared with a conventional scalar-potential finite-difference method. The induced electric field in a simple anatomical head model using our approach was in good agreement with finite element method for exposure to uniform magnetic field exposure and that from coil, simulating transcranial magnetic stimulation.Significance.The proposed tensor-conductance model demonstrated that the staircasing error in an inner target tissue of a voxel human body can be reduced. This finding can be used for the electromagnetic compliance assessment and dose evaluation in electric or magnetic stimulation at low frequencies.
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Affiliation(s)
- Yinliang Diao
- College of Electronic Engineering, College of Artificial Intelligence, South China Agricultural University, Guangzhou 510642, People's Republic of China
- Department of Electrical and Mechanical Engineering, Nagoya Institute of Technology, Nagoya 466-8555, Japan
| | - Li Liu
- College of Electronic Engineering, College of Artificial Intelligence, South China Agricultural University, Guangzhou 510642, People's Republic of China
| | - Nuo Deng
- College of Electronic Engineering, College of Artificial Intelligence, South China Agricultural University, Guangzhou 510642, People's Republic of China
| | - Shilei Lyu
- College of Electronic Engineering, College of Artificial Intelligence, South China Agricultural University, Guangzhou 510642, People's Republic of China
| | - Akimasa Hirata
- Department of Electrical and Mechanical Engineering, Nagoya Institute of Technology, Nagoya 466-8555, Japan
- Center of Biomedical Physics and Information Technology, Nagoya Institute of Technology, Nagoya 466-8555, Japan
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Firoozi A, Amphawan A, Khordad R, Mohammadi A, Jalali T, Edet CO, Ali N. Effect of nanoshell geometries, sizes, and quantum emitter parameters on the sensitivity of plasmon-exciton hybrid nanoshells for sensing application. Sci Rep 2023; 13:11325. [PMID: 37443203 DOI: 10.1038/s41598-023-38475-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2023] [Accepted: 07/09/2023] [Indexed: 07/15/2023] Open
Abstract
A proposed nanosensor based on hybrid nanoshells consisting of a core of metal nanoparticles and a coating of molecules is simulated by plasmon-exciton coupling in semi classical approach. We study the interaction of electromagnetic radiation with multilevel atoms in a way that takes into account both the spatial and the temporal dependence of the local fields. Our approach has a wide range of applications, from the description of pulse propagation in two-level media to the elaborate simulation of optoelectronic devices, including sensors. We have numerically solved the corresponding system of coupled Maxwell-Liouville equations using finite difference time domain (FDTD) method for different geometries. Plasmon-exciton hybrid nanoshells with different geometries are designed and simulated, which shows more sensitive to environment refractive index (RI) than nanosensor based on localized surface plasmon. The effects of nanoshell geometries, sizes, and quantum emitter parameters on the sensitivity of nanosensors to changes in the RI of the environment were investigated. It was found that the cone-like nanoshell with a silver core and quantum emitter shell had the highest sensitivity. The tapered shape of the cone like nanoshell leads to a higher density of plasmonic excitations at the tapered end of the nanoshell. Under specific conditions, two sharp, deep LSPR peaks were evident in the scattering data. These distinguishing features are valuable as signatures in nanosensors requiring fast, noninvasive response.
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Affiliation(s)
- A Firoozi
- Department of Physics, College of Sciences, Yasouj University, Yasouj, 75918, Iran
| | - Angela Amphawan
- Smart Photonics Research Laboratory, Sunway University, 47500, Sunway, Selangor, Malaysia.
- Future Cities Research Institute, Sunway University, 47500, Sunway, Selangor, Malaysia.
| | - R Khordad
- Department of Physics, College of Sciences, Yasouj University, Yasouj, 75918, Iran.
| | - A Mohammadi
- Department of Physics, Persian Gulf University, Bushehr, 75196, Iran
| | - T Jalali
- Department of Physics, Persian Gulf University, Bushehr, 75196, Iran
| | - C O Edet
- Institute of Engineering Mathematics, Universiti Malaysia Perlis, 02600, Arau, Perlis, Malaysia
- Faculty of Electronic Engineering Technology, Universiti Malaysia Perlis, 02600, Arau, Perlis, Malaysia
- Department of Physics, Cross River University of Technology, Calabar, Nigeria
| | - N Ali
- Department of Physics, Cross River University of Technology, Calabar, Nigeria
- Advanced Communication Engineering (ACE) Centre of Excellence, Universiti Malaysia Perlis, 01000, Kangar, Perlis, Malaysia
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Zhao Q, Sarris CD. Generalized tensor FDTD method for sloped dispersive interfaces and thin sheets. OPTICS EXPRESS 2019; 27:15812-15826. [PMID: 31163772 DOI: 10.1364/oe.27.015812] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Accepted: 04/18/2019] [Indexed: 06/09/2023]
Abstract
We present a modified formulation of the Finite-Difference Time-Domain (FDTD) technique that facilitates the accurate modeling of curved plasmonic interfaces. These interfaces appear in structures of interest for the design of optical metamaterials, such as arrays of plasmonic nanorods. Our approach uses the standard rectangular FDTD mesh and tensor effective permittivities for the interface cells, implicitly enforcing field boundary conditions, and is readily applicable to thin curved dispersive layers. We demonstrate the accuracy and effectiveness of our approach with the periodic analysis of a silver nanorod array and the computation of scattering parameters from a thin dispersive ring in a waveguide.
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Abstract
The basic theoretical understanding of light interacting with nanostructured metals that has existed since the early 1900s has become more relevant in the last two decades, largely because of new approaches to structure metals down to the nanometer scale or smaller. Here, a broad overview of the concepts and applications of nanostructuring metals for light-based technologies is given. The theory of the response of metals to an applied oscillating field is given, including a discussion of nonlocal, nonlinear and quantum effects. Using this metal response, the guiding of electromagnetic (light) waves using metals is given, with a particular emphasis on the impact of nanostructured metals for tighter confinement and slower propagation. Similarly, the influence of metal nanostructures on light scattering by isolated metal structures, like nanoparticles and nanoantennas, is described, with basic results presented including plasmonic/circuit resonances, the single channel limit, directivity enhancement, the maximum power transfer theorem, limits on the magnetic response from kinetic inductance and the scaling of gap plasmons to the nanometer scale and smaller. A brief overview of nanofabrication approaches to creating metal nanostructures is given. Finally, existing and emerging light-based applications are presented, including those for sensing, spectroscopy (including local refractive index, Raman, IR absorption), detection (including Schottky detectors), switching (including terahertz photoconductive antennas), modulation, energy harvesting and photocatalysis, light emission (including lasers and tunneling based light emission), optical tweezing, nonlinear optics, subwavelength imaging and lithography and high density data storage.
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Lesina AC, Vaccari A, Berini P, Ramunno L. On the convergence and accuracy of the FDTD method for nanoplasmonics. OPTICS EXPRESS 2015; 23:10481-10497. [PMID: 25969089 DOI: 10.1364/oe.23.010481] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Use of the Finite-Difference Time-Domain (FDTD) method to model nanoplasmonic structures continues to rise - more than 2700 papers have been published in 2014 on FDTD simulations of surface plasmons. However, a comprehensive study on the convergence and accuracy of the method for nanoplasmonic structures has yet to be reported. Although the method may be well-established in other areas of electromagnetics, the peculiarities of nanoplasmonic problems are such that a targeted study on convergence and accuracy is required. The availability of a high-performance computing system (a massively parallel IBM Blue Gene/Q) allows us to do this for the first time. We consider gold and silver at optical wavelengths along with three "standard" nanoplasmonic structures: a metal sphere, a metal dipole antenna and a metal bowtie antenna - for the first structure comparisons with the analytical extinction, scattering, and absorption coefficients based on Mie theory are possible. We consider different ways to set-up the simulation domain, we vary the mesh size to very small dimensions, we compare the simple Drude model with the Drude model augmented with two critical points correction, we compare single-precision to double-precision arithmetic, and we compare two staircase meshing techniques, per-component and uniform. We find that the Drude model with two critical points correction (at least) must be used in general. Double-precision arithmetic is needed to avoid round-off errors if highly converged results are sought. Per-component meshing increases the accuracy when complex geometries are modeled, but the uniform mesh works better for structures completely fillable by the Yee cell (e.g., rectangular structures). Generally, a mesh size of 0.25 nm is required to achieve convergence of results to ∼ 1%. We determine how to optimally setup the simulation domain, and in so doing we find that performing scattering calculations within the near-field does not necessarily produces large errors but reduces the computational resources required.
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Zhao S. High-order FDTD methods for transverse electromagnetic systems in dispersive inhomogeneous media. OPTICS LETTERS 2011; 36:3245-3247. [PMID: 21847222 DOI: 10.1364/ol.36.003245] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
This Letter introduces a novel finite-difference time-domain (FDTD) formulation for solving transverse electromagnetic systems in dispersive media. Based on the auxiliary differential equation approach, the Debye dispersion model is coupled with Maxwell's equations to derive a supplementary ordinary differential equation for describing the regularity changes in electromagnetic fields at the dispersive interface. The resulting time-dependent jump conditions are rigorously enforced in the FDTD discretization by means of the matched interface and boundary scheme. High-order convergences are numerically achieved for the first time in the literature in the FDTD simulations of dispersive inhomogeneous media.
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Affiliation(s)
- Shan Zhao
- Department of Mathematics, University of Alabama, Tuscaloosa, Alabama 35487, USA.
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Halas NJ, Lal S, Chang WS, Link S, Nordlander P. Plasmons in Strongly Coupled Metallic Nanostructures. Chem Rev 2011; 111:3913-61. [DOI: 10.1021/cr200061k] [Citation(s) in RCA: 2420] [Impact Index Per Article: 186.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Naomi J. Halas
- Department of Electrical and Computer Engineering, ‡Department of Chemistry, and §Department of Physics and Astronomy, Rice University, Houston, Texas 77005, United States
| | - Surbhi Lal
- Department of Electrical and Computer Engineering, ‡Department of Chemistry, and §Department of Physics and Astronomy, Rice University, Houston, Texas 77005, United States
| | - Wei-Shun Chang
- Department of Electrical and Computer Engineering, ‡Department of Chemistry, and §Department of Physics and Astronomy, Rice University, Houston, Texas 77005, United States
| | - Stephan Link
- Department of Electrical and Computer Engineering, ‡Department of Chemistry, and §Department of Physics and Astronomy, Rice University, Houston, Texas 77005, United States
| | - Peter Nordlander
- Department of Electrical and Computer Engineering, ‡Department of Chemistry, and §Department of Physics and Astronomy, Rice University, Houston, Texas 77005, United States
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