Durham, NC, United States

Wave Computation Technologies, Inc.

www.wavenology.com
Durham, NC, United States
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Deng C.,Xiamen University | Luo M.,Wave Computation Technologies, Inc. | Yuan M.,Wave Computation Technologies, Inc. | Zhao B.,Wave Computation Technologies, Inc. | And 2 more authors.
Journal of Computational Acoustics | Year: 2017

The perfectly matched layer (PML) absorbing boundary condition has been proven to absorb body waves and surface waves very efficiently at non-grazing incidence. However, the traditional PML would generate large spurious reflections at grazing incidence, for example, when the sources are located near the truncating boundary and the receivers are at a large offset. In this paper, a new PML implementation is presented for the boundary truncation in three-dimensional spectral element time domain (SETD) for solving acoustic wave equations. This method utilizes pseudospectral time-domain (PSTD) method to solve first-order auxiliary differential equations (ADEs), which is more straightforward than that in the classical FEM framework. © 2017 © IMACS


Niu J.,Duke University | Luo M.,Wave Computation Technologies, Inc. | Zhu J.,Xiamen University | Liu Q.H.,Duke University
Optics Express | Year: 2015

Graphene's relatively poor absorption is an essential obstacle for designing graphene-based photonic devices with satisfying photo-responsivity. To enhance the tunable light absorption of graphene, appropriate excitation of localized surface plasmon resonance is considered as a promising approach. In this work, the strategy of incorporating periodic cuboid gold nanoparticle (NP) cluster arrays and cylindrical gold NP arrays with Bragg reflectors into graphene-based photodetectors are theoretically studied by the boundary-integral spectral element method (BI-SEM). With the BI-SEM, the models can be numerically analyzed with excellent accuracy and efficiency. Numerical simulation shows that the proposed structures can effectively engineer the light absorption in graphene by tuning plasmon resonance. In the spectra of 300 nm to 1000 nm, a maximum light absorption of 67.54% is observed for the graphene layer with optimal parameters of the photodetector model. © 2015 Optical Society of America.


Niu J.,Duke University | Liu Q.H.,Duke University | Luo M.,Wave Computation Technologies, Inc. | Zhu J.,Xiamen University
IEEE Antennas and Propagation Society, AP-S International Symposium (Digest) | Year: 2015

Graphene's relatively poor absorption is an essential obstacle for designing graphene-based photonic devices with satisfying photo-responsivity. To enhance the tunable light absorption of graphene, appropriate excitation of localized surface plasmon resonance is considered as a promising approach. In this work, the strategy of incorporating periodic cylindrical gold nanoparticle (NP) cluster arrays with Bragg reflectors into graphene-based photodetectors are theoretically studied by the boundary-integral spectral element method (BI-SEM). With the BI-SEM, the models can be numerically analyzed with excellent accuracy and efficiency. Numerical simulation shows that the proposed structures can effectively engineer the light absorption in graphene by tuning plasmon resonance. In the spectra of 300 nm to 1000 nm, a maximum light absorption of 76.13% is observed for the graphene layer with optimal parameters of the photodetector model, while that of 54.68% is observed at the edge of visible spectra. © 2015 IEEE.


Wang L.,Duke University | Yuan M.,Duke University | Xiao T.,Wave Computation Technologies, Inc. | Joines W.T.,Duke University | Liu Q.H.,Duke University
IEEE Antennas and Wireless Propagation Letters | Year: 2011

Using dual high-speed memristors, we report on an efficient broadband electromagnetic radiation from a narrowband microstrip patch antenna. The directly modulated microstrip patch antenna system with dual memristors is calculated by using an integrated full-wave finite-difference time-domain method with an embedded SPICE3 solver. Nonlinear transient electromagnetic response is analyzed. The radiation frequency spectrum demonstrates the broadband radiation performance from the narrowband antenna system. © 2011 IEEE.


Niu J.,Duke University | Liu Q.H.,Duke University | Luo M.,Wave Computation Technologies, Inc.
IEEE Antennas and Propagation Society, AP-S International Symposium (Digest) | Year: 2015

Over the past decades, a few prototype of graphene-based optoelectronic devices have been proposed because of graphene's remarkable optical and mechanical properties. However, few tools are available for analyzing graphene's nonlinear optical performance within practical designs, despite its strong third harmonic generation (THG) has drawn intensive attention in theoretical and experimental study. In this work, a full-wave solver is proposed for the THG problem. Based on boundary-integral spectral element solvers, the proposal numerical method shows relatively fast convergence and high accuracy. In addition, as a typical example, several prototypes of graphene-based photodetectors are studied for their THG emission as stored energy. © 2015 IEEE.


Niu J.,Duke University | Luo M.,Wave Computation Technologies, Inc. | Liu Q.H.,Duke University
2015 USNC-URSI Radio Science Meeting (Joint with AP-S Symposium), USNC-URSI 2015 - Proceedings | Year: 2015

Graphene has drawn strong interest and intensive study because of its remarkable electromagnetic, thermal, and mechanical properties. As a crucial property, graphene's nonlinear optical performance is an emerging topic in theoretical and experimental studies. Recent investigations shows that despite its one-atom thickness, single layer graphene's nonlinear optical response is particularly strong. Due to the centrosymmetric structure, the ideal floating single layer graphene forbids the emission of second harmonic generation (SHG) of optical fields. However, in practical designs, the symmetric property may be broken by its adjacent materials, which makes the induced SHG optical behavior interesting. On the contrary, the third order nonlinear optical effects in graphene are reported as remarkably strong. Originated from the resonant nature of the light-graphene interaction, the effective third-order susceptibility arrives on the order of χ(3) ∼ 10-15m2/V2. This strong third order optical interaction generates a third harmonic signal with a significant contrast between graphene and the background material in most optoelectronic designs. © 2015 IEEE.


Niu J.,Duke University | Luo M.,Wave Computation Technologies, Inc. | Liu Q.H.,Duke University
Journal of the Optical Society of America B: Optical Physics | Year: 2016

Although graphene's particularly strong third-order susceptibility has drawn intensive attention in theoretical and experimental studies, its low bulk nonlinear response heavily emphasizes the nanostructure's design for a sufficient magnitude of third-harmonic generation (THG). Meanwhile, currently few tools are available for accurate theoretical analyses of graphene's nonlinear performance within a relatively complex structure, which renders the design of graphene-based nonlinear optoelectronic devices even more challenging. In this work, a high-accuracy self-consistent numerical solver based on the boundary-integral spectral element method is first proposed for the THG problem. Starting from the coupled vector wave equations, the proposed solver solves for the fundamental frequency field and third-harmonic field together iteratively, and it covers the optical/electro-optic Kerr effects ignored by most previous THG studies. After validating the proposed method with the comparison between numerical results and experimental data, we extend our study to the THG enhancement strategy with ultrastrong localized surface plasmon resonances (LSPRs) and Kerr effects. For both optical and electro-optic Kerr effects, the systematic simulation is performed for graphene's THG within the incident spectra of 400-1000 nm. Compared with the THG of floating single-atom-layer graphene, numerical results show that under specific LSPR engineering, graphene's THG backward emission is enhanced by 4.4 × 105 times. Simultaneously applying the electro-optic Kerr process can further boost the THG emission. However, its contribution is only secondary compared with LSPR. This study is also extended to bilayer and trilayer graphene models under strong LSPR. © 2016 Optical Society of America.


Grant
Agency: Department of Defense | Branch: Navy | Program: STTR | Phase: Phase II | Award Amount: 732.87K | Year: 2011

Wave Computation Technologies and Duke University will develop minimally coupled, co-mingled E and B field antennas through numerical and experimental investigations based on first-principle theories. The project objectives are to (a) develop the simulation capability for modeling superconducting quantum interference filter devices and the related B field antennas, (b) make appropriate designs of co-mingled E and B antennas, and (c) experimentally verify and improve these designs. The numerical simulation will also include the superconducting and quantum mechanic effects in the B field antennas; thus, this project will provide a new tool to determine the optimal configurations of individual E and B field antennas and the arrays formed by such antennas. Based on the successful development of 1D and simple 2D SQIF array modeling capabilities, in Phase 2, we will develop sophisticated 2D SQIF array simulation capabilities for magnetic field antennas, as well as multiscale simulation capabilities for electric field antennas in the near field based on our enhanced new commercial electromagnetic field software package Wavenology EM. With this tool we will determine the mutual coupling and isolation levels from a variety of combinations of E field and B field transmitters/receivers, and the dependence on scanning parameters such as the scan angle. We will also experimentally verify the designed co-mingled E and B field antennas.


Grant
Agency: Department of Defense | Branch: Navy | Program: STTR | Phase: Phase I | Award Amount: 100.00K | Year: 2010

Wave Computation Technologies and Duke University will develop minimally coupled, co-mingled E and B field antennas through numerical and experimental investigations based on both phenomenological and first-principle theories. The project objectives are to (a) develop the simulation capability for modeling superconducting quantum interference filter devices and the related B field antennas, (b) make appropriate designs of co-mingled E and B antennas, and (c) experimentally verify and improve these designs. The numerical simulation will also include the superconducting and quantum mechanic effects in the B field antennas; thus, this project will provide a new tool to determine the optimal configurations of individual E and B field antennas and the arrays formed by such antennas. In Phase 1, we will develop an initial simulation capability for both electric and magnetic field antennas in the near field based on our enhanced new commercial electromagnetic field software package Wavenology EM. With this tool we will determine the mutual coupling and isolation levels from a variety of combinations of E field and B field transmitters/receivers, and the dependence on scanning parameters such as the scan angle. By the end of Phase 1, we will have several candidates for the co-mingled E and B field antennas.


Grant
Agency: Department of Defense | Branch: Navy | Program: SBIR | Phase: Phase I | Award Amount: 70.00K | Year: 2010

Wave Computation Technologies, Inc. (WCT) proposes to develop a new time-domain discontinuous Galerkin software tool for modeling electromagnetic wave propagation through complex material and configurations. This solver combines the discontinuous Galerkin (DG) method with the finite-element time-domain (FETD) method to allow discontinuous discretization of complex geometry and materials. The solver will be implemented for arbitrary anistropoic and dispersive meda, so that novel materials including metamaterials can be included in the design simulation. The DG-FETD solver is highly efficient for complicated problems because it allows independent meshing and resolution for different regions. The WCT team has extensive experience with the relevant computational electromagnetics algorithms, and is in an excellent position to develop such a computational electromagnetics software tool. The proposed time-domain solver will further extend the application domain of the conventional finite element method to include large array of frequency selective surfaces and other complex electromagnetic environments.

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