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(76) Production(s) de GUIZAL B.


Efficient computation of EM scattering from a dielectric cylinder covered with graphene strips
Auteur(s): Guizal B., Jeyar Y., Antezza M.
Conférence invité: The 14th International Conference “Micro and Nanoelectronics – 2021” (ICMNE2021) (Zvenigorod, Moscow Region, RU, 20211004)
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Résumé: We present a numerical approach for the solution of EM scattering from a dielectric cylinder partially covered with graphene. It is based on a classical FourierBessel expansion of the fields inside and outside the cylinder to which we apply the adhoc boundary conditions in the presence of graphene. Due to the singular nature of the electric field at the ends of the graphene sheet, we introduce auxiliary boundary conditions to better take this reality into account. The result is a very simple and very efficient method allowing the study of diffraction from such structures.



Efficient computation of EM scattering from a dielectric cylinder covered with graphene strips for heat transfer
Auteur(s): Jeyar Y., Antezza M., Guizal B.
Conference: European Optical Society : Annual Meeting 2021 (EOSAM2021) (Rome, IT, 20210913)
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Résumé: We present a numerical approach for the solution of EM scattering from a dielectric cylinder partially covered with graphene. It is based on a clas sical FourierBessel expansion of the fields inside and outside the cylinder to which we apply the adhoc boundary conditions in the presence of graphene. Due to the singular nature of the electric field at the ends of the graphene sheet, we introduce auxiliary boundary conditions to better take this reality into ac count. The result is a very simple and very efficient method allowing the study of diffraction from such structures. Our ultimate goal is to apply this approach to radiative heat transfer between graphene coated cylinders and planes.



Strong geometry dependence of the Casimir force between interpenetrated rectangular gratings
Auteur(s): Wang Mingkang, Tang Lu, Messina C. Y. Ng Riccardo, Guizal B., Crosse J. a., Antezza M., Chan Che ting, Chan Ho bun
(Article) Publié:
Nature Communications, vol. 12 p.600 (2021)
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DOI: 10.1038/s41467021208914
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Résumé: Quantum fluctuations give rise to Casimir forces between two parallel conducting plates, the magnitude of which increases monotonically as the separation decreases. By introducing nanoscale gratings to the surfaces, recent advances have opened opportunities for controlling the Casimir force in complex geometries. Here, we measure the Casimir force between two rectangular silicon gratings. Using an onchip detection platform, we achieve accurate alignment between the two gratings so that they interpenetrate as the separation is reduced. Just before interpenetration occurs, the measured Casimir force is found to have a geometry dependence that is much stronger than previous experiments, with deviations from the proximity force approximation reaching a factor of ~500. After the gratings interpenetrate each other, the Casimir force becomes nonzero and independent of displacement. This work shows that the presence of gratings can strongly modify the Casimir force to control the interaction between nanomechanical components.



Manybody effective thermal conductivity in phasechange nanoparticle chains due to nearfield radiative heat transfer
Auteur(s): Luo M., Zhao Junming, Liu Linhua, Guizal B., Antezza M.
(Article) Publié:
International Journal Of Heat And Mass Transfer, vol. 166 p.120793 (2020)
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DOI: 10.1016/j.ijheatmasstransfer.2020.120793
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Résumé: In dense systems composed of numerous nanoparticles, direct simulations of nearfield radiative heat transfer (NFRHT) require considerable computational resources. NFRHT for the simple onedimensional nanoparticle chains embedded in a nonabsorbing host medium is investigated from the point of view of the continuum by means of an approach combining the manybody radiative heat transfer theory and the Fourier law. Effects of the phase change of the insulatormetal transition material (), the complex manybody interaction (MBI) and the host medium relative permittivity on the characteristic effective thermal conductivity (ETC) are analyzed. The ETC for nanoparticle chains below the transition temperature can be as high as 50 times of that above the transition temperature due to the phase change effect. The strong coupling in the insulatorphase nanoparticle chain accounts for its high ETC as compared to the low ETC for the chain at the metallic phase, where there is a mismatch between the characteristic thermal frequency and resonance frequency. The strong MBI is in favor of the ETC. For SiC nanoparticle chains, the MBI even can double the ETC as compared to those without considering the MBI effect. For the dense chains, a strong MBI enhances the ETC due to the strong interparticles couplings. When the chains go more and more dilute, the MBI can be neglected safely due to negligible couplings. The host medium relative permittivity significantly affects the interparticles couplings, which accounts for the permittivitydependent ETC for the nanoparticle chains.



Inverse design of a 1D dielectric metasurface by topology optimization: fluctuationstrend analysis assisted by a diamondsquare algorithm
Auteur(s): Edee Kofi, Ben rhouma Maha, Fan Jonathan albert, Antezza M., Gippius N. a., Wang E., Plumey JeanPierre, Granet G., Guizal B.
(Article) Publié:
Journal Of The Optical Society Of America B, vol. 37 p.3721 (2020)
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DOI: 10.1364/JOSAB.405030
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Résumé: We present a topology optimization method for a 1D dielectric metasurface, coupling the classical fluctuations trend analysis (FTA) and diamondsquare algorithm (DSA). In classical FTA, a couple of device distributions termed fluctuation or mother and trends or father, with specific spectra, is initially generated. The spectral prop erties of the trend function allow one to efficiently target the basin of optimal solutions. For optimizing a 1D metasurface to deflect a normally incident plane wave into a given deflecting angle, a cosinelike function has been identified to be an optimal father profile, allowing one to efficiently target a basin of local minima. However, there is no efficient method to predict the father profile number of oscillations that effectively allows one to avoid undesirable local optima. It would be natural to suggest a randomization of the variable that controls the number of oscillations of the father function. However, one of the main drawbacks of the randomness searching process is that, combined with a gradient method, the algorithm can target undesirable local minima. The method proposed in this paper improves the possibility of classical FTA to avoid the trapping of undesirable local optimal solutions. This is accomplished by extending the initial candidate family to higherquality offspring that are generated due to the DSA. Doing so ensures that the main features of the best trends are stored in the genes of all offspring structures.



Giant Casimir Torque between Rotated Gratings and the θ = 0 Anomaly
Auteur(s): Antezza M., Chan Ho bun, Guizal B., Marachevskii V., Messina R., Wang Mingkang
(Article) Publié:
Physical Review Letters, vol. 124 p.013903 (2020)
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DOI: 10.1103/PhysRevLett.124.013903
WoS: 000505997600005
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2 Citations
Résumé: We study the Casimir torque between two metallic onedimensional gratings rotated by an angle θ with respect to each other. We find that, for infinitely extended gratings, the Casimir energy is anomalously discontinuous at θ 1⁄4 0, due to a critical zeroorder geometric transition between a 2D and a 1Dperiodic system. This transition is a peculiarity of the grating geometry and does not exist for intrinsically anisotropic materials. As a remarkable practical consequence, for finitesize gratings, the torque per area can reach extremely large values, increasing without bounds with the size of the system. We show that for finite gratings with only ten period repetitions, the maximum torque is already 60 times larger than the one predicted in the case of infinite gratings. These findings pave the way to the design of a contactless quantum vacuum torsional spring, with possible relevance to micro and nanomechanical devices.



Longrange Heat and Energy Transfer through Hyperbolic Materials
Auteur(s): Biehs SvendAge, Messina R., Guizal B., Antezza M., Benabdallah Philippe, Deshmukh R., Galfsky T., Menon V, Agarwal G. S.
Conférence invité: PIERS 2019 (Rome, IT, 20190620)
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Résumé: Heat flux exchanged between two hot bodies at subwavelength separation distances can exceed the limitpredicted by the blackbody theory. However, this superPlanckian transfer is restricted to these separationdistances. Here we demonstrate the possible existence of a superPlanckian transfer at arbitrary large separationdistances if the interacting bodies are connected in the near field with weakly dissipating hyperbolic waveguides.This result opens the way to longdistance transport of nearfield thermal energy.
