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Li, Xi, Joseph Smalley, Zhitong Li e Qing Gu. "Effective Modal Volume in Nanoscale Photonic and Plasmonic Near-Infrared Resonant Cavities". Applied Sciences 8, n.º 9 (25 de agosto de 2018): 1464. http://dx.doi.org/10.3390/app8091464.
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We survey expressions of the effective modal volume, Veff, commonly used in the literature for nanoscale photonic and plasmonic cavities. We apply different expressions of Veff to several canonical cavities designed for nanoscale near-infrared light sources, including metallo-dielectric and coaxial geometries. We develop a metric for quantifying the robustness of different Veff expressions to the different cavities and materials studied. We conclude that no single expression for Veff is universally applicable. Several expressions yield nearly identical results for cavities with well-confined photonic-type modes. For cavities with poor confinement and a low quality factor, however, expressions using the proper normalization method need to be implemented to adequately describe the diverging behavior of their effective modal volume. The results serve as a practical guideline for mode analysis of nanoscale optical cavities, which show promise for future sensing, communication, and computing platforms.
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Melchior, Pascal, Deirdre Kilbane, Ernst Jan Vesseur, Albert Polman e Martin Aeschlimann. "Photoelectron imaging of modal interference in plasmonic whispering gallery cavities". Optics Express 23, n.º 25 (30 de novembro de 2015): 31619. http://dx.doi.org/10.1364/oe.23.031619.
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Dell’Ova, Florian, Yoann Brulé, Nicolas Gros, Justin Bizouard, Diana Shakirova, Aurélie Bertaux, Ouassila Narsis-Labbani et al. "Compact implementation of an all-optical 1-bit full adder by coherent excitation of a single 3-µm2 plasmonic cavity". EPJ Web of Conferences 287 (2023): 04014. http://dx.doi.org/10.1051/epjconf/202328704014.
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In contrast to the high performances of long-range, high-speed optical information transfer, optical information processing remains outperformed by electronic microprocessing. The two mains reasons are the lack of gain medium that hampers the development of an optical analogue of the transistor and the lack of compactness of the approaches proposed so far. Here, we demonstrate a new concept of the design of all-optical elementary computing units based on the shaping of plasmonic modal landscape in micrometric on-chip 2D cavities to realize reconfigurable Arithmetic and Logic Units (ALU). Our interconnect-free devices perform multi-bit logic gate functions in a single cavity without ALU cascading, therefore obviating loss in vias and so the need for gain to restore the binary signal. Moreover, an astute cavity design allows to reconfigure a single cavity into multiple logic functions, including a first full adder. The main challenge on the way to increasing the functional Boolean complexity is the design of the cavity shape and of the excitation/detection parameters for which an approach based on artificial intelligence will be implemented.
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Berkhout, Annemarie, e A. Femius Koenderink. "A simple transfer-matrix model for metasurface multilayer systems". Nanophotonics 9, n.º 12 (4 de julho de 2020): 3985–4007. http://dx.doi.org/10.1515/nanoph-2020-0212.
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AbstractIn this work we present a simple transfer-matrix based modeling tool for arbitrarily layered stacks of resonant plasmonic metasurfaces interspersed with dielectric and metallic multilayers. We present the application of this model by analyzing three seminal problems in nanophotonics. These are the scenario of perfect absorption in plasmonic Salisbury screens, strong coupling of microcavity resonances with the resonance of plasmon nano-antenna metasurfaces, and the hybridization of cavities, excitons and metasurface resonances.
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Sain, Basudeb, Roy Kaner, Yaara Bondy e Yehiam Prior. "Plasmonic flat surface Fabry-Perot interferometry". Nanophotonics 7, n.º 3 (23 de fevereiro de 2018): 635–41. http://dx.doi.org/10.1515/nanoph-2017-0082.
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AbstractWe report measurements of the optical transmission through a plasmonic flat surface interferometer. The transmission spectrum shows Fabry-Perot-like modes, where for each mode order, the maximal transmission occurs at a gap that grows linearly with wavelength, giving the appearance of diagonal dependence on gap and wavelength. The experimental results are supported by numerical solutions of the wave equations and by a simplified theoretical model that is based on the coupling between localized and propagating surface plasmon. This work explains not only the appearance of the modes but also their sharp dependence on the gap, taking into consideration the refractive indices of the surrounding media. The transmission spectra provide information about the phase difference between the light impinging on the two cavities, enabling interferometric measurement of the light phase by transmission through the coupled plasmonic cavities. The 1° phase-difference resolution is obtained without any propagation distance, thus making this interferometer suitable for on-chip operation.
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Schmidt, Mikołaj K., Ruben Esteban, Felix Benz, Jeremy J. Baumberg e Javier Aizpurua. "Linking classical and molecular optomechanics descriptions of SERS". Faraday Discussions 205 (2017): 31–65. http://dx.doi.org/10.1039/c7fd00145b.
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The surface-enhanced Raman scattering (SERS) of molecular species in plasmonic cavities can be described as an optomechanical process where plasmons constitute an optical cavity of reduced effective mode volume which effectively couples to the vibrations of the molecules. An optomechanical Hamiltonian can address the full quantum dynamics of the system, including the phonon population build-up, the vibrational pumping regime, and the Stokes–anti-Stokes correlations of the photons emitted. Here we describe in detail two different levels of approximation to the methodological solution of the optomechanical Hamiltonian of a generic SERS configuration, and compare the results of each model in light of recent experiments. Furthermore, a phenomenological semi-classical approach based on a rate equation of the phonon population is demonstrated to be formally equivalent to that obtained from the full quantum optomechanical approach. The evolution of the Raman signal with laser intensity (thermal, vibrational pumping and instability regimes) is accurately addressed when this phenomenological semi-classical approach is properly extended to account for the anti-Stokes process. The formal equivalence between semi-classical and molecular optomechanics descriptions allows us to describe the vibrational pumping regime of SERS through the classical cross sections which characterize a nanosystem, thus setting a roadmap to describing molecular optomechanical effects in a variety of experimental situations.
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Bahadori, Meisam, Ali Eshaghian, Hossein Hodaei, Mohsen Rezaei e Khashayar Mehrany. "Analysis and Design of Optical Demultiplexer Based on Arrayed Plasmonic Slot Cavities: Transmission Line Model". IEEE Photonics Technology Letters 25, n.º 8 (abril de 2013): 784–86. http://dx.doi.org/10.1109/lpt.2013.2250951.
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Palstra, Isabelle M., Hugo M. Doeleman e A. Femius Koenderink. "Hybrid cavity-antenna systems for quantum optics outside the cryostat?" Nanophotonics 8, n.º 9 (16 de maio de 2019): 1513–31. http://dx.doi.org/10.1515/nanoph-2019-0062.
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AbstractHybrid cavity-antenna systems have been proposed to combine the sub-wavelength light confinement of plasmonic antennas with microcavity quality factors Q. Here, we examine what confinement and Q can be reached in these hybrid systems, and we address their merits for various applications in classical and quantum optics. Specifically, we investigate their applicability for quantum-optical applications at noncryogenic temperatures. To this end we first derive design rules for hybrid resonances from a simple analytical model. These rules are benchmarked against full-wave simulations of hybrids composed of state-of-the-art nanobeam cavities and plasmonic-dimer gap antennas. We find that hybrids can outperform the plasmonic and cavity constituents in terms of Purcell factor, and additionally offer freedom to reach any Q at a similar Purcell factor. We discuss how these metrics are highly advantageous for a high Purcell factor, yet weak-coupling applications, such as bright sources of indistinguishable single photons. The challenges for room-temperature strong coupling, however, are far more daunting: the extremely high dephasing of emitters implies that little benefit can be achieved from trading confinement against a higher Q, as done in hybrids. An attractive alternative could be strong coupling at liquid nitrogen temperature, where emitter dephasing is lower and this trade-off can alleviate the stringent fabrication demands required for antenna strong coupling. For few-emitter strong-coupling, high-speed and low-power coherent or incoherent light sources, particle sensing and vibrational spectroscopy, hybrids provide the unique benefit of very high local optical density of states, tight plasmonic confinement, yet microcavity Q.
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Medina, I., e A. Villaseñor. "A comparative analysis between Drude and Johnson & Christy for nanometric optical demultiplexer". Journal of Physics: Conference Series 2475, n.º 1 (1 de abril de 2023): 012010. http://dx.doi.org/10.1088/1742-6596/2475/1/012010.
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Abstract The constant need to miniaturize technological devices has increased the development of novel optical devices in the nanoscale. A common kind of photonic devices are built using Metal-Insulator-Metal (MIM) interfaces to generate Surface Plasmons Polaritons (SPPs) and process light waves in the optical window. In this paper a 12 channel demultiplexer is proposed using 8 cavities coupled to both sides of the main waveguide. Then the nano demultiplexer is modelled in COMSOL Multiphysics using Drude model and Johnson and Christy parameters for the optical constants. Then we compare the transmission spectrum from 400 to 2200 nm for both models and discuss the differences advantages of each method.
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Wang, Bo-Yun, Zi-Hao Zhu, You-Kang Gao, Qing-Dong Zeng, Yang Liu, Jun Du, Tao Wang e Hua-Qing Yu. "Plasmon induced transparency effect based on graphene nanoribbon waveguide side-coupled with rectangle cavities system". Acta Physica Sinica 71, n.º 2 (2022): 024201. http://dx.doi.org/10.7498/aps.71.20211397.
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In order to reduce the size of the device and realize the ultrafast response time and dynamic tunableness, the single-band and dual-band plasmon induced transparency (PIT) effect are investigated based on graphene nanoribbon waveguide side-coupled rectangle cavity. The slow light properties of the model are analyzed numerically and theoretically by coupled mode theory and finite difference time domain method. With controlling the chemical potential of the graphene rectangle cavity, the tunability of the resonant wavelength and the transmission peak can be achieved simultaneously in single-band and dual-band PIT model. As the chemical potential of graphene increases, the resonant wavelength of each transmission window of PIT effect decreases gradually and presents the blue shift. In addition, through dynamically tuning the resonant wavelength of the graphene rectangle cavity, when the chemical potential of the graphene rectangle cavity increases from 0.41 to 0.44 eV, the group index of single PIT system is controlled to be between 79.2 and 28.3, and the tunable bandwidth is 477 nm. Moreover, the group index of dual PIT system is controlled to be between 143.2 and 108.6 when the chemical potentials of graphene rectangle cavities 1, 2, and 3 are 0.39–0.42 eV, 0.40–0.43 eV, and 0.41–0.44 eV, respectively. The size of the entire PIT structure is <0.5 μm<sup>2</sup>. The research results here in this work are of reference significance in designing and fabricating the optical sensors, optical filters, slow light and light storage devices with ultrafast, ultracompact and dynamic tunableness.
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Hainey, Mel F., Takaaki Mano, Takeshi Kasaya, Tetsuyuki Ochiai, Hirotaka Osato, Kazuhiro Watanabe, Yoshimasa Sugimoto et al. "Systematic studies for improving device performance of quantum well infrared stripe photodetectors". Nanophotonics 9, n.º 10 (4 de julho de 2020): 3373–84. http://dx.doi.org/10.1515/nanoph-2020-0095.
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AbstractThe integration of quantum well infrared photodetectors with plasmonic cavities has allowed for demonstration of sensitive photodetectors in the mid-infrared up to room-temperature operating conditions. However, clear guidelines for optimizing device structure for these detectors have not been developed. Using simple stripe cavity detectors as a model system, we clarify the fundamental factors that improve photodetector performance. By etching semiconductor material between the stripes, the cavity resonance wavelength was expected to blue-shift, and the electric field was predicted to strongly increase, resulting in higher responsivity than unetched stripe detectors. Contrary to our predictions, etched stripe detectors showed lower responsivities, indicating surface effects at the sidewalls and reduced absorption. Nevertheless, etching led to higher detectivity due to significantly reduced detector dark current. These results suggest that etched structures are the superior photodetector design, and that appropriate sidewall surface treatments could further improve device performance. Finally, through polarization and incidence angle dependence measurements of the stripe detectors, we clarify how the design of previously demonstrated wired patch antennas led to improved device performance. These results are widely applicable for cavity designs over a broad range of wavelengths within the infrared, and can serve as a roadmap for improving next-generation infrared photodetectors.
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Li, Huiyu, Lin Zhao, Guangwei Chen, Guoqing Hu e Zhehai Zhou. "Multilayer Metamaterials with Vertical Cavities for High-Efficiency Transmittance with Metallic Components in the Visible Spectrum". Photonics 11, n.º 10 (11 de outubro de 2024): 956. http://dx.doi.org/10.3390/photonics11100956.
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Metasurfaces are opening promising flexibilities to reshape the wavefront of electromagnetic waves. Notable optical phenomena are observed with the tailored surface plasmon, which is excited by metallic components in the visible spectrum. However, metamaterial or metasurface devices utilizing metallic materials encounter the challenge of low transmission efficiency, particularly within the visible spectrum. This study proposes a multilayer design strategy to enhance their transmission efficiency. By incorporating additional metal layers for improvements in the transmission efficiency and dielectric layers as spacers, cavities are formed along the propagation direction, enabling the modulation of transmittance and reflection through a process mimicking destructive interference. An analytical model simplified with the assumption of deep-subwavelength-thick metal layers is proposed to predict the structural parameters with optimized transmittance. Numerical studies employing the rigorous coupled wave analysis method confirmed that the additional metal layers significantly improve the transmittance. The introduction of the extra metal and dielectric layers enhances the transmission efficiency in specific spectral regions, maintaining a controllable passband and transmittance. The results indicate that the precise control over the layers’ thicknesses facilitates the modulation of peak-to-valley ratios and the creation of comb-like filters, which can be further refined through controlled random variation in the thickness. Furthermore, when the thickness of the silver layer followed an arithmetic sequence, a multilayer structure with a transmittance of approximately 80% covering the entire visible spectrum could be achieved. Significantly, the polarization extinction ratio and the phase delay of the incident beams could still be modulated by adjusting the geometrical structure and parameters of the multilayer metamaterial for diversified functionalities.
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Doğan, Mustafa, e Kazım Yavuz Ekşi. "Stimulated emission–based model of fast radio bursts". Monthly Notices of the Royal Astronomical Society 494, n.º 1 (13 de março de 2020): 876–84. http://dx.doi.org/10.1093/mnras/staa708.
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ABSTRACT Fast radio bursts (FRBs) are bright, short-duration radio transients with very high brightness temperatures implying highly coherent emission. We suggest that the FRBs are caused by the self-focusing of an electron beam interacting with an ambient plasma right beyond the light cylinder radius of a neutron star. The magnetic field at the light cylinder radius is relatively high that can accommodate both young Crab-like systems and old millisecond pulsars addressing the diverse environments of FRBs. At the first stage, the intense pulsed-beam passing through the background plasma causes instabilities such that the trapped particles in local Buneman-type cavitons saturate the local field. The beam is then radially self-focused due to the circular electric field developed by the two-stream instability that leads to Weibel instability in the transverse direction. Finally, the non-linear saturation of the Weibel instability results in the self-modulational formation of solitons due to plasmoid instability. The resonant solitary waves are the breather-type solitons hosting relativistic particles with self-excited oscillations. The analytical solutions obtained for non-linear dispersion and solitons suggest that, near the current sheets, the relativistic bunches are accelerated/amplified by klystron-like structures due to self-excited oscillations by the induced local electric field. Boosted coherent radio emission propagates through a narrow cone with strong focusing due to radial electric field and magnetic pinching. The non-linear evolution of solitons and the stimulated emission are associated with the Buneman instability and the possibility of the presence of nanosecond shots in FRBs are investigated.
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Yim, Ju Eun, Zachary T. Brawley e Matthew T. Sheldon. "Subradiant plasmonic cavities make bright polariton states dark". Nanophotonics, 22 de março de 2024. http://dx.doi.org/10.1515/nanoph-2024-0058.
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Abstract Nanostructured plasmonic surfaces allow for precise tailoring of electromagnetic modes within sub-diffraction mode volumes, boosting light–matter interactions. This study explores vibrational strong coupling (VSC) between molecular ensembles and subradiant “dark” cavities that support infrared quadrupolar plasmonic resonances (QPLs). The QPL mode exhibits a dispersion characteristic of bound states in the continuum (BIC). That is, the mode is subradiant or evanescent at normal incidence and acquires increasing “bright” dipole character with larger in-plane wavevectors. We deposited polymethyl methacrylate (PMMA) thin films on QPL substrates to induce VSC with the carbonyl stretch in PMMA and measured the resulting infrared (IR) spectra. Our computational analysis predicts the presence of “dark” subradiant polariton states within the near-field of the QPL mode, and “bright” collective molecular states. This finding is consistent with classical and quantum mechanical descriptions of VSC that predict hybrid polariton states with cavity-like modal character and N−1 collective molecular states with minimal cavity character. However, the behaviour is opposite of what is standardly observed in VSC experiments that use “bright” cavities, which results in “bright” polariton states that can be spectrally resolved as well as N−1 collective molecular states that are spectrally absent. Our experiments confirm a reduction of molecular absorption and other spectral signatures of VSC with the QPL mode. In comparison, our experiments promoting VSC with dipolar plasmonic resonances (DPLs) reproduce the conventional behavior. Our results highlight the significance of cavity mode symmetry in modifying the properties of the resultant states from VSC, while offering prospects for direct experimental probing of the N−1 molecule-like states that are usually spectrally “dark”.
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Lu, Yu-Wei, Wen-Jie Zhou, Yongyao Li, Runhua Li, Jing-Feng Liu, Lin Wu e Haishu Tan. "Unveiling atom-photon quasi-bound states in hybrid plasmonic-photonic cavity". Nanophotonics, 9 de junho de 2022. http://dx.doi.org/10.1515/nanoph-2022-0162.
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Abstract Dissipation, often associated with plasmons, leads to decoherence and is generally considered fatal for quantum nonlinearities and entanglement. Counterintuitively, by introducing a dissipative plasmonic nanoantenna into a typical cavity quantum electrodynamics (QED) system, we unveil the wide existence of the atom-photon quasi-bound state (qBS), a kind of exotic eigenstate with anomalously small decay, in the hybrid plasmonic-photonic cavity. To derive the analytical condition of atom-photon qBS, we formulate a quantized two-mode model of the local density of states by connecting the interacting uncoupled cavity modes to the macroscopic QED. With resonant plasmon-photon coupling, we showcase the single-atom qBS that improves the efficiency of single-photon generation over one order of magnitude; and the two-atom qBS that significantly enhances spontaneous entanglement generation compared with a bare photonic cavity. Notably, such single-atom and multi-atom qBS can be simultaneously accessed in realistic plasmonic-photonic cavities, providing a versatile platform for advanced quantum technologies, such as quantum light sources, quantum computation, and quantum information.
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Gupta, Satyendra Nath, Ora Bitton, Tomas Neuman, Ruben Esteban, Lev Chuntonov, Javier Aizpurua e Gilad Haran. "Complex plasmon-exciton dynamics revealed through quantum dot light emission in a nanocavity". Nature Communications 12, n.º 1 (26 de fevereiro de 2021). http://dx.doi.org/10.1038/s41467-021-21539-z.
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AbstractPlasmonic cavities can confine electromagnetic radiation to deep sub-wavelength regimes. This facilitates strong coupling phenomena to be observed at the limit of individual quantum emitters. Here, we report an extensive set of measurements of plasmonic cavities hosting one to a few semiconductor quantum dots. Scattering spectra show Rabi splitting, demonstrating that these devices are close to the strong coupling regime. Using Hanbury Brown and Twiss interferometry, we observe non-classical emission, allowing us to directly determine the number of emitters in each device. Surprising features in photoluminescence spectra point to the contribution of multiple excited states. Using model simulations based on an extended Jaynes-Cummings Hamiltonian, we find that the involvement of a dark state of the quantum dots explains the experimental findings. The coupling of quantum emitters to plasmonic cavities thus exposes complex relaxation pathways and emerges as an unconventional means to control dynamics of quantum states.
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Sánchez-Pérez, Francisco, Olivia Borrell-Grueiro, Alfredo Casasnovas-Melián, Diego J. Ramos-Ramos, Andrés Guerrero-Martínez, Luis Bañares, Alejandro Prada et al. "Formation of hollow silver nanoparticles under irradiation with ultrashort laser pulses". Nanophotonics, 16 de fevereiro de 2024. http://dx.doi.org/10.1515/nanoph-2023-0881.
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Abstract We have studied the formation of cavities in spherical silver nanoparticles embedded in silica, irradiated with fs laser pulses that produce an intense electronic excitation. Experimentally determined aspect ratio, i.e. the ratio between the cavity and nanoparticle size, for hollow structures formed under different irradiation conditions shows a very good agreement with values obtained by means of atomistic simulations. According to the predictions of the atomistic model, one can produce at will hollow silver nanoparticles with cavities of tailored dimensions, having an accurate control. Hence, laser irradiation can be used to control and design the optical response by tuning the localized surface plasmon resonances of the hollow nanoparticles.
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Tang, DingKang. "Tunable Fano resonance in a novel compact metal-insulator-metal structure". Journal of Optics, 7 de maio de 2024. http://dx.doi.org/10.1088/2040-8986/ad4802.
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Abstract A novel compact scheme to realize tunable Fano resonance is proposed and investigated theoretically and numerically. The scheme is based on two slot cavities in a metal-insulator-metal (MIM) structure. The model and formation mechanism of Fano resonance in this structure are studied. A new method based on four-mode temporal coupled-mode theory (TCMT) is used to analyze model of the structure with two slot cavities. The formation mechanism of Fano resonance in the proposed scheme is due to the plasmon-induced transparency (PIT) phenomenon in the structure. To the best of our knowledge, this formation mechanism of Fano resonance is revealed for the first time. The tunability and slow light phenomenon in the new structure are also studied. It is believed that research in this article can provide a new method to achieve Fano resonance. Furthermore, it is helpful to establish the Fano resonance model and reveal the formation mechanism of Fano resonance.
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Litman, Yair, Venkat Kapil, Yotam M. Y. Feldman, Davide Tisi, Tomislav Begušić, Karen Fidanyan, Guillaume Fraux et al. "i-PI 3.0: A flexible and efficient framework for advanced atomistic simulations". Journal of Chemical Physics 161, n.º 6 (14 de agosto de 2024). http://dx.doi.org/10.1063/5.0215869.
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Atomic-scale simulations have progressed tremendously over the past decade, largely thanks to the availability of machine-learning interatomic potentials. These potentials combine the accuracy of electronic structure calculations with the ability to reach extensive length and time scales. The i-PI package facilitates integrating the latest developments in this field with advanced modeling techniques thanks to a modular software architecture based on inter-process communication through a socket interface. The choice of Python for implementation facilitates rapid prototyping but can add computational overhead. In this new release, we carefully benchmarked and optimized i-PI for several common simulation scenarios, making such overhead negligible when i-PI is used to model systems up to tens of thousands of atoms using widely adopted machine learning interatomic potentials, such as Behler–Parinello, DeePMD, and MACE neural networks. We also present the implementation of several new features, including an efficient algorithm to model bosonic and fermionic exchange, a framework for uncertainty quantification to be used in conjunction with machine-learning potentials, a communication infrastructure that allows for deeper integration with electronic-driven simulations, and an approach to simulate coupled photon-nuclear dynamics in optical or plasmonic cavities.
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Vornicescu, Doru, Virgil Penta e Michael Keusgen. "An analytical tooth model based on SPR chips coated with hydroxyapatite used for investigation of the acquired dental pellicle". physica status solidi (a), 5 de setembro de 2023. http://dx.doi.org/10.1002/pssa.202300146.
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One of the main targets in modern dentistry is the prevention of caries. Not only daily nutrition plays an important role, but also the so called “pellicle” on the outer surfaced of teeth, which is mainly formed by saliva proteins. Moreover, numerous bacteria are part of this pellicle, which might cause caries by acidic metabolites. In the here presented study, a method for electrophoretic deposition (EPD) of hydroxyapatite (HAP) nanoparticles on gold surfaces, suitable for Surface Plasmon Resonance (SPR) measurements has been developed. An “artificial tooth” has been created and loaded by natural saliva in different concentrations (to form a natural pellicle), while the influence of an environment with different pH values has been studied. It could be demonstrated that even slight acid solutions damage the pellicle significantly within seconds, exposing the HAP to acidic degradation, which would lead to caries in the human oral cavities. This model allows to study pellicle formation as well as degradation in real time. As a practical example, the influence of beverages on the pellicle could be demonstrated.This article is protected by copyright. All rights reserved.
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Ren Yang, Li Zhen-Xiong, Zhang Lei, Cui Wei, Wu Xiong-Xiong, Huo Ya-Shan e He Zhi-Hui. "Tunable bound states in the continuous domain based on Fabry-Perot cavities and application studies". Acta Physica Sinica, 2024, 0. http://dx.doi.org/10.7498/aps.73.20240861.
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Excellent optical absorbers are always characterized by high quality factors and perfect absorption; however, these absorbers usually suffer from the ohmic losses due to conventional surface plasmon resonance, which limits their absorption performance in practical applications. To address the problem, a tunable bound state in the continuum (BIC) based on Fabry-Perot cavity is proposed in this paper. Figures 1(a) shows the structural model of the designed Fabry-Perot cavity absorber, which consists of Ag as the substrate, a layer of the dielectric material Al<sub>2</sub>O<sub>3</sub> above the Ag, and a high-refractive-index grating as the top dielectric layer Si ridge. By adjusting the thickness parameter <i>d</i> of Al<sub>2</sub>O<sub>3</sub>, the conversion of BIC and q-BIC is achieved in this paper, and when <i>d</i> is increased from 273 nm to 298 nm, the BIC can be transformed into quasi-BIC, and the perfect absorption of the absorber in the continuum spectrum can be increased to 100%, as shown in Figs. (b) and (c). In this paper, the factors affecting the perfect absorption are explored by using the interference theory; theoretical calculations of the quasi-BIC are carried out by using the coupled mode theory and impedance matching theory; the physical mechanism of the BIC is explained by using the electric and magnetic field theory, and the BIC is caused by the electric and magnetic dipole modes as well as the mirror image of the base Ag, which causes the interferential phase cancellation effect. Compared with the conventional absorber, the absorber has excellent structural parameter robustness and a wide range of BIC modulation. More importantly, the absorber has excellent sensing performance with a maximum sensitivity up to 34 nm/RIU and a maximum quality factor of 9.5. Last but not least, the absorber also achieves dual-frequency open-light performance, where the maximum modulation depth and the minimum insertion loss of the dual-frequency switch are 99.4% and 0.0004 dB, respectively. These findings have important implications in the fields of photonics, optical communications, and sensor technology.