plasmonic nanostructures
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2022 ◽  
Author(s):  
Yanming Feng ◽  
Zhiguo Li ◽  
Qiang Zhao ◽  
P P Chen ◽  
Jiqing Wang

Abstract Fano resonance and plasma induced transparency (PIT) have been widely observed in various plasmonic nanostructures. Fano resonance takes place in weak coupling regime where coupling constant between two electromagnetic modes is lower than damping constant of system. Hence, extracting coupling and damping coefficients from resonance spectrum is the key to distinguish between Fano resonance and other resonances. In this paper, we propose a simple and realizable coupled LC circuit to analyze Fano resonance and PIT. Weak and strong coupling regime are distinguished by comparing coupling constant with damping constant. Meanwhile, we gain deep insight into Fano resonance and PIT in circuit by analyzing circuit phase and understand their connection with resonance in photonic structure. Furthermore, we extend the equivalent circuit model to the field involved short-range plasmon polarization or multi-orders dark modes. Since there are no specific parameters associated with photonic nanostructure, the proposed equivalent circuit can be used in most plasmonic resonance system as an universal model.


Nanophotonics ◽  
2022 ◽  
Vol 0 (0) ◽  
Author(s):  
Zhiliang Zhang ◽  
Feng Zhao ◽  
Renxian Gao ◽  
Chih-Yu Jao ◽  
Churong Ma ◽  
...  

Abstract Plasmonic sensors exhibit tremendous potential to accomplish real-time, label-free, and high-sensitivity biosensing. Gold nanohole array (GNA) is one of the classic plasmonic nanostructures that can be readily fabricated and integrated into microfluidic platforms for a variety of applications. Even though GNA has been widely studied, new phenomena and applications are still emerging continuously expanding its capabilities. In this article, we demonstrated narrow-band high-order resonances enabled by Rayleigh anomaly in the nanohole arrays that are fabricated by scalable colloidal lithography. We fabricated large-area GNAs with different hole diameters, and investigated their transmission characteristics both numerically and experimentally. We showed that mode hybridization between the plasmon mode of the nanoholes and Rayleigh anomaly of the array could give rise to high-quality decapole resonance with a unique nearfield profile. We experimentally achieved a refractive index sensitivity, i.e., RIS up to 407 nm/RIU. More importantly, we introduced a spectrometer-free refractive index sensing based on lens-free smartphone imaging of GNAs with (intensity) sensitivity up to 137%/RIU. Using this platform, we realized the label-free detection of BSA molecules with concentration as low as 10−8 M. We believe our work could pave the way for highly sensitive and compact point-of-care devices with cost-effective and high-throughput plasmonic chips.


Nanomaterials ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 170
Author(s):  
Sneha Verma ◽  
Sunny Chugh ◽  
Souvik Ghosh ◽  
B. M. Azizur Rahman

The Artificial Neural Network (ANN) has become an attractive approach in Machine Learning (ML) to analyze a complex data-driven problem. Due to its time efficient findings, it has became popular in many scientific fields such as physics, optics, and material science. This paper presents a new approach to design and optimize the electromagnetic plasmonic nanostructures using a computationally efficient method based on the ANN. In this work, the nanostructures have been simulated by using a Finite Element Method (FEM), then Artificial Intelligence (AI) is used for making predictions of associated sensitivity (S), Full Width Half Maximum (FWHM), Figure of Merit (FOM), and Plasmonic Wavelength (PW) for different paired nanostructures. At first, the computational model is developed by using a Finite Element Method (FEM) to prepare the dataset. The input parameters were considered as the Major axis, a, the Minor axis, b, and the separation gap, g, which have been used to calculate the corresponding sensitivity (nm/RIU), FWHM (nm), FOM, and plasmonic wavelength (nm) to prepare the dataset. Secondly, the neural network has been designed where the number of hidden layers and neurons were optimized as part of a comprehensive analysis to improve the efficiency of ML model. After successfully optimizing the neural network, this model is used to make predictions for specific inputs and its corresponding outputs. This article also compares the error between the predicted and simulated results. This approach outperforms the direct numerical simulation methods for predicting output for various input device parameters.


Nanophotonics ◽  
2022 ◽  
Vol 0 (0) ◽  
Author(s):  
Young-Ho Jin ◽  
Juntaek Oh ◽  
Wonshik Choi ◽  
Myung-Ki Kim

Abstract Exploiting multiple near-field optical eigenmodes is an effective means of designing, engineering, and extending the functionalities of optical devices. However, the near-field optical eigenmodes of subwavelength plasmonic nanostructures are often highly multiplexed in both spectral and spatial distributions, making it extremely difficult to extract individual eigenmodes. We propose a novel mode analysis method that can resolve individual eigenmodes of subwavelength nanostructures, which are superimposed in conventional methods. A transmission matrix is constructed for each excitation wavelength by obtaining the near-field distributions for various incident angles, and through singular value decomposition, near-field profiles and energy spectra of individual eigenmodes are effectively resolved. By applying transmission matrix analysis to conventional electromagnetic simulations, we clearly resolved a set of orthogonal eigenmodes of single- and double-slot nanoantennas with a slot width of 20 nm. In addition, transmission matrix analysis leads to solutions that can selectively excite specific eigenmodes of nanostructures, allowing selective use of individual eigenmodes.


Nanophotonics ◽  
2022 ◽  
Vol 0 (0) ◽  
Author(s):  
Kyosuke Sakai ◽  
Hiroki Kitajima ◽  
Keiji Sasaki

Abstract Plasmonic nanostructures have considerable applicability in light–matter interactions owing to their capacity for strong field confinement and enhancement. Nanogap structures allow us to tailor electric field distributions at the nanoscale, bridging the differences in size and shape of atomic and light structures. In this study, we demonstrated that a plasmonic tetramer structure can squeeze structured light into a nanoscale area, in which a strong field gradient allows access to forbidden transitions. Numerical simulations showed that the gold tetramer structure on a glass substrate possesses a plasmonic eigenmode, which forms structured light with a quadrupole profile in the nanogap region at the center of the tetramer. The top–down technique employed using electron-beam lithography allows us to produce a gap size of approximately 50 nm, which supports plasmonic resonance in the near-infrared regime. In addition, we demonstrated an array architecture in which a collective lattice resonance enhances the intensity of the quadrupole field in multiple lattice units. This study highlights the possibility of accessing multipolar transitions in a combined system of structured light and plasmonic nanostructures. Our findings may lead to new platforms for spectroscopy, sensing, and light sources that take advantage of the full electronic spectrum of an emitter.


2022 ◽  
Author(s):  
Damien Eschimèse ◽  
François Vaurette ◽  
Céline Ha ◽  
Steve Arscott ◽  
Thierry Melin ◽  
...  

We explore numerically and experimentally the formation of hybridized modes between a bright mode displayed by a gold nanodisc and either dark or bright modes of a nanorod - both...


2022 ◽  
Author(s):  
Wenbing Wu ◽  
Matthias Pauly

This review presents the main techniques employed to construct chiral plasmonic materials and metasurfaces, in particular using soft-chemistry approaches, and discusses some applications of these nanostructures.


RSC Advances ◽  
2022 ◽  
Vol 12 (2) ◽  
pp. 845-859
Author(s):  
Mariacristina Turino ◽  
Nicolas Pazos-Perez ◽  
Luca Guerrini ◽  
Ramon A. Alvarez-Puebla

Integration of ligands equipped with quaternary amines on plasmonic surfaces generates positively-charged nanomaterials suitable for electrostatically binding negatively-charged species paving the way for their application in SERS sensing.


2022 ◽  
Author(s):  
Vikas Yadav ◽  
Soumik Siddhanta

Circular dichroism (CD) from plasmonic nanostructures yields fascinating insights into their chiroptical properties, however, the weak signals make their investigations profoundly challenging. We have demonstrated a method for significantly improving...


Sensors ◽  
2021 ◽  
Vol 22 (1) ◽  
pp. 236
Author(s):  
Rebeca Moldovan ◽  
Valentin Toma ◽  
Bogdan-Cezar Iacob ◽  
Rareș Ionuț Știufiuc ◽  
Ede Bodoki

Extensive effort and research are currently channeled towards the implementation of SERS (Surface Enhanced Raman Spectroscopy) as a standard analytical tool as it has undisputedly demonstrated a great potential for trace detection of various analytes. Novel and improved substrates are continuously reported in this regard. It is generally believed that plasmonic nanostructures with plasmon resonances close to the excitation wavelength (on-resonance) generate stronger SERS enhancements, but this finding is still under debate. In the current paper, we compared off-resonance gold nanobones (GNBs) with on-resonance GNBs and gold nanorods (GNRs) in both colloidal dispersion and as close-packed films self-assembled at liquid-liquid interface. Rhodamine 6G (R6G) was used as a Raman reporter in order to evaluate SERS performances. A 17-, 18-, and 55-fold increase in the Raman signal was observed for nanostructures (off-resonance GNBs, on-resonance GNBs, and on-resonance GNRs, respectively) assembled at liquid-liquid interface compared to the same nanostructures in colloidal dispersion. SERS performances of off-resonance GNBs were superior to on-resonance nanostructures in both cases. Furthermore, when off-resonance GNBs were assembled at the liquid interface, a relative standard deviation of 4.56% of the recorded signal intensity and a limit of detection (LOD) of 5 × 10−9 M could be obtained for R6G, rendering this substrate suitable for analytical applications.


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