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Araujo-Cabarcas, Juan CarlosORCID iD iconorcid.org/0000-0002-0143-5554
Publikasjoner (8 av 8) Visa alla publikasjoner
Araujo-Cabarcas, J. C., Engström, C. & Wadbro, E. (2023). Shape optimization for the strong routing of light in periodic diffraction gratings. Journal of Computational Physics, 472, Article ID 111684.
Åpne denne publikasjonen i ny fane eller vindu >>Shape optimization for the strong routing of light in periodic diffraction gratings
2023 (engelsk)Inngår i: Journal of Computational Physics, ISSN 0021-9991, E-ISSN 1090-2716, Vol. 472, artikkel-id 111684Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

In the quest for the development of faster and more reliable technologies, the ability to control the propagation, confinement, and emission of light has become crucial. The design of guide mode resonators and perfect absorbers has proven to be of fundamental importance. In this project, we consider the shape optimization of a periodic dielectric slab aiming at efficient directional routing of light to reproduce similar features of a guide mode resonator. For this, the design objective is to maximize the routing efficiency of an incoming wave. That is, the goal is to promote wave propagation along the periodic slab. A Helmholtz problem with a piecewise constant and periodic refractive index medium models the wave propagation, and an accurate Robin-to-Robin map models an exterior domain. We propose an optimal design strategy that consists of representing the dielectric interface by a finite Fourier formula and using its coefficients as the design variables. Moreover, we use a high order finite element (FE) discretization combined with a bilinear Transfinite Interpolation formula. This setting admits explicit differentiation with respect to the design variables, from where an exact discrete adjoint method computes the sensitivities. We show in detail how the sensitivities are obtained in the quasi-periodic discrete setting. The design strategy employs gradient-based numerical optimization, which consists of a BFGS quasi-Newton method with backtracking line search. As a test case example, we present results for the optimization of a so-called single port perfect absorber. We test our strategy for a variety of incoming wave angles and different polarizations. In all cases, we efficiently reach designs featuring high routing efficiencies that satisfy the required criteria.

sted, utgiver, år, opplag, sider
Elsevier, 2023
Emneord
Diffraction grating, Helmholtz problem, Light routing, Scattering problem, Shape optimization
HSV kategori
Identifikatorer
urn:nbn:se:umu:diva-200659 (URN)10.1016/j.jcp.2022.111684 (DOI)000879217600002 ()2-s2.0-85140226291 (Scopus ID)
Forskningsfinansiär
The Kempe Foundations, SMK-1857eSSENCE - An eScience CollaborationSwedish Research Council, 2021-04537
Tilgjengelig fra: 2022-11-07 Laget: 2022-11-07 Sist oppdatert: 2023-09-05bibliografisk kontrollert
Hamrin, M., Schillings, A., Opgenoorth, H. J., Nesbit-Östman, S., Krämer, E., Araújo, J. C., . . . Barnes, R. J. (2023). Space weather disturbances in non-stormy times: occurrence of dB/dt spikes during three solar cycles. Journal of Geophysical Research - Space Physics, 128(10), Article ID e2023JA031804.
Åpne denne publikasjonen i ny fane eller vindu >>Space weather disturbances in non-stormy times: occurrence of dB/dt spikes during three solar cycles
Vise andre…
2023 (engelsk)Inngår i: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 128, nr 10, artikkel-id e2023JA031804Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Spatio-temporal variations of ionospheric currents cause rapid magnetic field variations at ground level and Geomagnetically Induced Currents (GICs) that can be harmful for human infrastructure. The risk for large excursions in the magnetic field time derivative, “dB/dt spikes”, is known to be high during geomagnetic storms and substorms. However, less is known about the occurrence of spikes during non-stormy times. We use data from ground-based globally covering magnetometers (SuperMAG database) from the years 1985–2021. We investigate the spike occurrence (|dB/dt| > 100 nT/min) as a function of magnetic local time (MLT), magnetic latitude (Mlat), and the solar cycle phases during non-stormy times (−15 nT ≤ SYM-H < 0). We sort our data into substorm (AL < 200 nT) intervals (“SUB”) and less active intervals between consecutive substorms (“nonSUB”). We find that spikes commonly occur in both SUBs and nonSUBs during non-stormy times (3–23 spikes/day), covering 18–12 MLT and 65°–80° Mlat. This also implies a risk for infrastructure damage during non-stormy times, especially when several spikes occur nearby in space and time, possibly causing infrastructure weathering. We find that spikes are more common in the declining phase of the solar cycle, and that the occurrence of SUB spikes propagates from one midnight to one morning hotspot with ∼10 min in MLT for each minute in universal time (UTC). Finally, we discuss causes for the spikes in terms of spatio-temporal variations of ionospheric currents.

sted, utgiver, år, opplag, sider
American Geophysical Union (AGU), 2023
HSV kategori
Identifikatorer
urn:nbn:se:umu:diva-215270 (URN)10.1029/2023ja031804 (DOI)2-s2.0-85174460250 (Scopus ID)
Forskningsfinansiär
Swedish National Space Board, 81/17Swedish National Space Board, 108/18Swedish National Space Board, 194/19Swedish National Space Board, 118/17Swedish Research Council, 2018-03623Swedish Research Council, 2021-06683
Tilgjengelig fra: 2023-10-15 Laget: 2023-10-15 Sist oppdatert: 2023-10-30bibliografisk kontrollert
Araujo-Cabarcas, J. C. & Engström, C. (2021). On spurious solutions encountered in Helmholtz scatteringresonance computations in Rd with applications tonano-photonics and acoustics. Journal of Computational Physics, 429, Article ID 110024.
Åpne denne publikasjonen i ny fane eller vindu >>On spurious solutions encountered in Helmholtz scatteringresonance computations in Rd with applications tonano-photonics and acoustics
2021 (engelsk)Inngår i: Journal of Computational Physics, ISSN 0021-9991, E-ISSN 1090-2716, Vol. 429, artikkel-id 110024Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

In this paper, we consider a sorting scheme for potentially spurious scattering resonant pairs in one- and two-dimensional electromagnetic problems and in three-dimensional acoustic problems. The novel sorting scheme is based on a Lippmann-Schwinger type of volume integral equation and can, therefore, be applied to structures with graded materials as well as to configurations including piece-wise constant material properties. For TM/TE polarized electromagnetic waves and for acoustic waves, we compute first approximations of scattering resonances with finite elements. Then, we apply the novel sorting scheme to the computed eigenpairs and use it to mark potentially spurious solutions in electromagnetic and acoustic scattering resonances computations at a low computational cost. Several test cases with Drude-Lorentz dielectric resonators as well as with graded material properties are considered.

sted, utgiver, år, opplag, sider
Elsevier, 2021
Emneord
plasmon resonance, acoustic scattering resonances, resonance modes, nonlinear eigenvalue problems, Helmholtz problem, pseudospectrum, PML, DtN, leaky modes, resonant states, quasi-normal modes
HSV kategori
Identifikatorer
urn:nbn:se:umu:diva-159153 (URN)10.1016/j.jcp.2020.110024 (DOI)000618824400001 ()2-s2.0-85097236464 (Scopus ID)
Forskningsfinansiär
Swedish Research Council, 621-2012-3863
Merknad

Previously included in manuscript form, with title "Removal of spurious solutions encountered in Helmholtz scattering resonance computations in R^d".

Tilgjengelig fra: 2019-05-20 Laget: 2019-05-20 Sist oppdatert: 2021-09-10bibliografisk kontrollert
Araujo-Cabarcas, J. C. & Wadbro, E. (2021). Shape optimization for the strong directional scattering of dielectric nanorods. International Journal for Numerical Methods in Engineering, 122(15), 3683-3704
Åpne denne publikasjonen i ny fane eller vindu >>Shape optimization for the strong directional scattering of dielectric nanorods
2021 (engelsk)Inngår i: International Journal for Numerical Methods in Engineering, ISSN 0029-5981, E-ISSN 1097-0207, Vol. 122, nr 15, s. 3683-3704Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

In this project, we consider the shape optimization of a dielectric scatterer aiming at efficient directional routing of light. In the studied setting, light interacts with a penetrable scatterer with dimension comparable to the wavelength of an incoming planar wave. The design objective is to maximize the scattering efficiency inside a target angle window. For this, a Helmholtz problem with a piecewise constant refractive index medium models the wave propagation, and an accurate Dirichlet-to-Neumann map models an exterior domain. The strategy consists of using a high-order finite element (FE) discretization combined with gradient-based numerical optimization. The latter consists of a quasi-Newton (BFGS) with backtracking line search. A discrete adjoint method is used to compute the sensitivities with respect to the design variables. Particularly, for the FE representation of the curved shape, we use a bilinear transfinite interpolation formula, which admits explicit differentiation with respect to the design variables. We exploit this fact and show in detail how sensitivities are obtained in the discrete setting. We test our strategy for a variety of target angles, different wave frequencies, and refractive indexes. In all cases, we efficiently reach designs featuring high scattering efficiencies that satisfy the required criteria.

sted, utgiver, år, opplag, sider
John Wiley & Sons, 2021
Emneord
directional scattering, Helmholtz problem, light routing, scattering problem, shape optimization
HSV kategori
Identifikatorer
urn:nbn:se:umu:diva-183008 (URN)10.1002/nme.6677 (DOI)000646710100001 ()2-s2.0-85104290944 (Scopus ID)
Forskningsfinansiär
The Kempe Foundations, SMK-1857eSSENCE - An eScience Collaboration
Tilgjengelig fra: 2021-05-18 Laget: 2021-05-18 Sist oppdatert: 2022-01-12bibliografisk kontrollert
Araujo-Cabarcas, J. C., Campos, C., Engström, C. & Roman, J. E. (2020). Computation of scattering resonances in absorptive and dispersive media with applications to metal-dielectric nano-structures. Journal of Computational Physics, 407, Article ID 109220.
Åpne denne publikasjonen i ny fane eller vindu >>Computation of scattering resonances in absorptive and dispersive media with applications to metal-dielectric nano-structures
2020 (engelsk)Inngår i: Journal of Computational Physics, ISSN 0021-9991, E-ISSN 1090-2716, Vol. 407, artikkel-id 109220Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

In this paper we consider scattering resonance computations in optics when the resonators consist of frequency dependent and lossy materials, such as metals at optical frequencies. The proposed computational approach combines a novel hp-FEM strategy, based on dispersion analysis for complex frequencies, with a fast implementation of the nonlinear eigenvalue solver NLEIGS. Numerical computations illustrate that the pre-asymptotic phase is significantly reduced compared to standard uniform h and p strategies. Moreover, the efficiency grows with the refractive index contrast, which makes the new strategy highly attractive for metal-dielectric structures. The hp-refinement strategy together with the efficient parallel code result in highly accurate approximations and short runtimes on multi processor platforms.

sted, utgiver, år, opplag, sider
Elsevier, 2020
Emneord
Plasmon resonance, Resonance modes, Nonlinear eigenvalue problems, Helmholtz problem, PML, Dispersion analysis, leaky modes, resonant states, quasimodes, quasi-normal modes
HSV kategori
Identifikatorer
urn:nbn:se:umu:diva-159151 (URN)10.1016/j.jcp.2019.109220 (DOI)000519535500017 ()2-s2.0-85078588641 (Scopus ID)
Merknad

Originally included in thesis in manuscript form

Tilgjengelig fra: 2019-05-20 Laget: 2019-05-20 Sist oppdatert: 2023-03-24bibliografisk kontrollert
Araujo-Cabarcas, J. C. (2019). Reliable hp finite element computations of scattering resonances in nano optics. (Doctoral dissertation). Umeå: Umeå Universitet
Åpne denne publikasjonen i ny fane eller vindu >>Reliable hp finite element computations of scattering resonances in nano optics
2019 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

Eigenfrequencies are commonly studied in wave propagation problems, as they are important in the analysis of closed cavities such as a microwave oven. For open systems, energy leaks into infinity and therefore scattering resonances are used instead of eigenfrequencies. An interesting application where resonances take an important place is in whispering gallery mode resonators.

The objective of the thesis is the reliable and accurate approximation of scattering resonances using high order finite element methods. The discussion focuses on the electromagnetic scattering resonances in metal-dielectric nano-structures using a Drude-Lorentz model for the description of the material properties. A scattering resonance pair satisfies a reduced wave equationand an outgoing wave condition. In this thesis, the outgoing wave condition is replaced by a Dirichlet-to-Neumann map, or a Perfectly Matched Layer. For electromagnetic waves and for acoustic waves, the reduced wave equation is discretized with finite elements. As a result, the scattering resonance problem is transformed into a nonlinear eigenvalue problem.

In addition to the correct approximation of the true resonances, a large number of numerical solutions that are unrelated to the physical problem are also computed in the solution process. A new method based on a volume integral equation is developed to remove these false solutions.

The main results of the thesis are a novel method for removing false solutions of the physical problem, efficient solutions of non-linear eigenvalue problems, and a new a-priori based refinement strategy for high order finite element methods. The overall material in the thesis translates into a reliable and accurate method to compute scattering resonances in physics and engineering.

sted, utgiver, år, opplag, sider
Umeå: Umeå Universitet, 2019. s. 35
Serie
Research report in mathematics, ISSN 1653-0810 ; 67
Emneord
Scattering resonances, Helmholtz problems, pseudospectrum, Lippmann-Schwinger equation, finite element methods, nonlinear eigenvalue problems, spurious solutions
HSV kategori
Identifikatorer
urn:nbn:se:umu:diva-159154 (URN)978-91-7855-076-0 (ISBN)
Disputas
2019-06-13, MA121, MIT-huset, Umeå, 13:00 (engelsk)
Opponent
Veileder
Tilgjengelig fra: 2019-05-23 Laget: 2019-05-20 Sist oppdatert: 2019-05-21bibliografisk kontrollert
Araujo-Cabarcas, J. C., Engström, C. & Jarlebring, E. (2018). Efficient resonance computations for Helmholtz problems based on a Dirichlet-to-Neumann map. Journal of Computational and Applied Mathematics, 330, 177-192
Åpne denne publikasjonen i ny fane eller vindu >>Efficient resonance computations for Helmholtz problems based on a Dirichlet-to-Neumann map
2018 (engelsk)Inngår i: Journal of Computational and Applied Mathematics, ISSN 0377-0427, E-ISSN 1879-1778, Vol. 330, s. 177-192Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

We present an efficient procedure for computing resonances and resonant modes of Helmholtz problems posed in exterior domains. The problem is formulated as a nonlinear eigenvalue problem (NEP), where the nonlinearity arises from the use of a Dirichlet-to-Neumann map, which accounts for modeling unbounded domains. We consider a variational formulation and show that the spectrum consists of isolated eigenvalues of finite multiplicity that only can accumulate at infinity. The proposed method is based on a high order finite element discretization combined with a specialization of the Tensor Infinite Arnoldi method (TIAR). Using Toeplitz matrices, we show how to specialize this method to our specific structure. In particular we introduce a pole cancellation technique in order to increase the radius of convergence for computation of eigenvalues that lie close to the poles of the matrix-valued function. The solution scheme can be applied to multiple resonators with a varying refractive index that is not necessarily piecewise constant. We present two test cases to show stability, performance and numerical accuracy of the method. In particular the use of a high order finite element discretization together with TIAR results in an efficient and reliable method to compute resonances.

sted, utgiver, år, opplag, sider
Amsterdam: Elsevier, 2018
Emneord
Nonlinear eigenvalue problems, Helmholtz problem, Scattering resonances, Dirichlet-to-Neumann map, Arnoldi's method, Matrix functions
HSV kategori
Forskningsprogram
matematik
Identifikatorer
urn:nbn:se:umu:diva-138325 (URN)10.1016/j.cam.2017.08.012 (DOI)000415783000014 ()2-s2.0-85029359070 (Scopus ID)
Tilgjengelig fra: 2017-08-21 Laget: 2017-08-21 Sist oppdatert: 2023-03-24bibliografisk kontrollert
Araujo-Cabarcas, J. C. & Engström, C. (2017). On spurious solutions in finite element approximations of resonances in open systems. Computers and Mathematics with Applications, 74(10), 2385-2402
Åpne denne publikasjonen i ny fane eller vindu >>On spurious solutions in finite element approximations of resonances in open systems
2017 (engelsk)Inngår i: Computers and Mathematics with Applications, ISSN 0898-1221, E-ISSN 1873-7668, Vol. 74, nr 10, s. 2385-2402Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

In this paper, we discuss problems arising when computing resonances with a finite element method. In the pre-asymptotic regime, we detect for the one dimensional case, spurious solutions in finite element computations of resonances when the computational domain is truncated with a perfectly matched layer (PML) as well as with a Dirichlet-to-Neumann map (DtN). The new test is based on the Lippmann–Schwinger equation and we use computations of the pseudospectrum to show that this is a suitable choice. Numerical simulations indicate that the presented test can distinguish between spurious eigenvalues and true eigenvalues also in difficult cases.

sted, utgiver, år, opplag, sider
Elsevier, 2017
Emneord
Scattering resonances, Lippmann–Schwinger equation, Nonlinear eigenvalue problems, Acoustic resonator, Dielectric resonator, Bragg resonator
HSV kategori
Forskningsprogram
matematik
Identifikatorer
urn:nbn:se:umu:diva-138096 (URN)10.1016/j.camwa.2017.07.020 (DOI)000415908400013 ()2-s2.0-85026531962 (Scopus ID)
Forskningsfinansiär
Swedish Research Council, 621-2012-3863
Tilgjengelig fra: 2017-08-09 Laget: 2017-08-09 Sist oppdatert: 2023-03-23bibliografisk kontrollert
Organisasjoner
Identifikatorer
ORCID-id: ORCID iD iconorcid.org/0000-0002-0143-5554