scholarly journals Plasmonic mode coupling and thin film sensing in metal–insulator–metal structures

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
N. Andam ◽  
S. Refki ◽  
S. Hayashi ◽  
Z. Sekkat
Keyword(s):  
Thin Film ◽  
Refractive Index ◽  
Mode Coupling ◽  
Interaction Analysis ◽  
Biomolecular Interaction ◽  
Plasmonic Mode ◽  
Air Interface ◽  
Highly Sensitive ◽  
Modes Coupling ◽  
Better Than

AbstractOptical sensors based on surface plasmon resonance (SPR) in the attenuated total reflection (ATR) configuration in layered media have attracted considerable attention over the past decades owing to their ability of label free sensing in biomolecular interaction analysis, and highly sensitive detection of changes in refractive index and thickness, i.e. the optical thickness, of thin film adsorbates (thin film sensing). Furthermore, SPR is highly sensitive to the refractive index of the medium adjacent to the bare metal, and it allows for bulk sensing as well. When deposited at the metal/air interface, an adsorbed layer disturbs the highly localized, i.e. bound, wave at this interface and changes the plasmon resonance to allow for sensing in angular or wavelength interrogation and intensity measurement modes. A high degree of sensitivity is required for precise and efficient sensing, especially for biomolecular interaction analysis for early stage diagnostics; and besides conventional SPR (CSPR), several other configurations have been developed in recent years targeting sensitivity, including long-range SPR (LRSPR) and waveguide-coupled SPR (WGSPR) observed in MIM structures, referred here to by MIM modes, resulting from the coupling of SPRs at I/M interfaces, and Fano-type resonances occurring from broad and sharp modes coupling in layered structures. In our previous research, we demonstrated that MIM is better than CSPR for bulk sensing, and in this paper, we show that CSPR is better than MIM for thin film sensing for thicknesses of the sensing layer (SL) larger than 10 nm. We discuss and compare the sensitivity of CSPR and MIM for thin film sensing by using both experiments and theoretical calculations based on rigorous electromagnetic (EM) theory. We discuss in detail MIM modes coupling and anti-crossing, and we show that when a thin film adsorbate, i.e. a SL), is deposited on top of the outermost-layer of an optimized MIM structure, it modifies the characteristics of the coupled modes of the structure, and it reduces the electric field, both inside the SL and at the SL/air interface, and as a result, it decreases the sensitivity of the MIM versus the CSPR sensor. Our work is of critical importance to plasmonic mode coupling using MIM configurations, as well as to optical bio- and chemical-sensing.

scholarly journals High Sensitivity Terahertz Biosensor Based on Mode Coupling of a Graphene/Bragg Reflector Hybrid Structure

Biosensors ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 377
Author(s):  
Yamei Liu ◽  
Qiwen Zheng ◽  
Hongxia Yuan ◽  
Shenping Wang ◽  
Keqiang Yin ◽  
...  
Keyword(s):  
Refractive Index ◽  
Mode Coupling ◽  
Defect Mode ◽  
High Sensitivity ◽  
Hybrid Structure ◽  
Transmission Peak ◽  
Bragg Reflector ◽  
Highly Sensitive ◽  
Specific Parameter ◽  
Resonance Transmission

In this work, a high-sensitivity terahertz (THz) biosensor is achieved by using a graphene/Bragg reflector hybrid structure. This high-sensitivity THz biosensor is developed from the sharp Fano resonance transmission peak created by coupling the graphene Tamm plasmons (GTPs) mode to a defect mode. It is found that the proposed THz biosensor is highly sensitive to the Fermi energy of graphene, as well as the thickness and refractive index of the sensing medium. Through specific parameter settings, the composite structure can achieve both a liquid biosensor and a gas biosensor. For the liquid biosensor, the maximum sensitivity of >1000°/RIU is obtained by selecting appropriate parameters. We believe the proposed layered hybrid structure has the potential to fabricate graphene-based high-sensitivity biosensors.

A Three-Dimensional Tetraphenylethylene-Based Fluorescence Covalent Organic Framework for Molecular Recognition

2020 ◽  
Author(s):  
Junxia Ren ◽  
Yaozu Liu ◽  
Xin Zhu ◽  
Yangyang Pan ◽  
Yujie Wang ◽  
...  
Keyword(s):  
Molecular Recognition ◽  
Fluorescence Probe ◽  
Three Dimensional ◽  
Hazardous Substances ◽  
Covalent Organic Framework ◽  
Highly Sensitive ◽  
Volatile Organic ◽  
Polycyclic Aromatic ◽  
Better Than ◽  
Organic Framework

<p><a></a><a></a><a></a><a></a><a></a><a></a><a></a><a>The development of highly-sensitive recognition of </a><a></a><a></a><a></a><a></a><a>hazardous </a>chemicals, such as volatile organic compounds (VOCs) and polycyclic aromatic hydrocarbons (PAHs), is of significant importance because of their widespread social concerns related to environment and human health. Here, we report a three-dimensional (3D) covalent organic framework (COF, termed JUC-555) bearing tetraphenylethylene (TPE) side chains as an aggregation-induced emission (AIE) fluorescence probe for sensitive molecular recognition.<a></a><a> </a>Due to the rotational restriction of TPE rotors in highly interpenetrated framework after inclusion of dimethylformamide (DMF), JUC-555 shows impressive AIE-based strong fluorescence. Meanwhile, owing to the large pore size (11.4 Å) and suitable intermolecular distance of aligned TPE (7.2 Å) in JUC-555, the obtained material demonstrates an excellent performance in the molecular recognition of hazardous chemicals, e.g., nitroaromatic explosives, PAHs, and even thiophene compounds, via a fluorescent quenching mechanism. The quenching constant (<i>K</i><sub>SV</sub>) is two orders of magnitude better than those of other fluorescence-based porous materials reported to date. This research thus opens 3D functionalized COFs as a promising identification tool for environmentally hazardous substances.</p>

Comparative crosstalk performance analysis of different configurations of heterogeneous multicore fiber

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Umar Farooque ◽  
Rakesh Ranjan
Keyword(s):  
Refractive Index ◽  
Mode Coupling ◽  
The Other ◽  
Heterogeneous Multicore ◽  
Coupled Mode ◽  
The Core ◽  
Bending Radius ◽  
Multicore Fiber ◽  
The Impact ◽  
Core Pitch

AbstractIn order to select the heterogeneous multicore fiber (MCF) configuration with ultra-low crosstalk and low peak bending radius, comparative crosstalk analysis have been done for the three possible core configurations, namely, Configuration 1 - different refractive index (R.I.) and different radius, Configuration 2 - different R.I., and Configuration 3 - different radius. Using the coupled mode equation and the simplified expressions of mode coupling coefficient (MCC) for different configurations of heterogeneous cores, the crosstalk performance of all the heterogeneous MCF configurations along with the homogeneous MCF have been investigated analytically with respect to core pitch (D) and fiber bending radius (${R}_{b}$). Further, these expressions of MCC have been extended to obtain the simplified expressions of MCC for the estimation of crosstalk levels in respective trench-assisted (TA) heterogeneous MCF configurations. It is observed from the analysis that in Configuration 1, crosstalk level is lowest and the rate of decrease in the crosstalk with respect to the core pitch is highest compared to the other configurations of heterogeneous MCF. The values of crosstalk obtained analytically have been validated by comparing it with the values obtained from finite element method (FEM) based numerical simulation results. Further, we have investigated the impact of a fixed percent change (5%) in the core parameters (radius and/or R.I.) of one of the core of a homogeneous MCF, to realize the different heterogeneous MCF configurations, on the variations in crosstalk levels, difference in the mode effective refractive index of the core 1 and core 2 ($\Delta {n}_{eff}={n}_{eff1}-{n}_{eff2}$), and the peak bending radius (${R}_{pk}$). For the same percent variations (5%) in the core parameters (radius and/or R.I.) of different configurations of cores (Config. 1-Config. 3), Config. 1 MCF has highest variation in $\Delta {n}_{eff}$ value compared to other configurations of MCF. Further, this highest variation in $\Delta {n}_{eff}$ value of Config. 1 MCF results in smallest peak bending radius. The smaller value of peak bending radius allows MCF to bend into smaller radius. Therefore, Configuration 1 is the potential choice for the design of MCF with smaller peak bending radius and ultra-low crosstalk level compared to the other configurations of SI-heterogeneous MCF.

scholarly journals Nanoimprinted multifunctional nanoprobes for a homogeneous immunoassay in a top-down fabrication approach

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Hubert Brueckl ◽  
Astrit Shoshi ◽  
Stefan Schrittwieser ◽  
Barbara Schmid ◽  
Pia Schneeweiss ◽  
...  
Keyword(s):  
Thin Film ◽  
Nanoimprint Lithography ◽  
Thin Film Deposition ◽  
Film Deposition ◽  
In Vitro Diagnostics ◽  
Top Down ◽  
Highly Sensitive ◽  
Optical And Magnetic Properties ◽  
Lift Off

AbstractMultifunctional nanoparticles are discussed as versatile probes for homogeneous immunoassays for in-vitro diagnostics. Top-down fabrication allows to combine and tailor magnetic and plasmonic anisotropic properties. The combination of nanoimprint lithography, thin film deposition, and lift-off processing provides a top-down fabrication platform, which is both flexible and reliable. Here, we discuss the material compositions and geometrical designs of monodisperse multicomponent nanoparticles and their consequences on optical and magnetic properties. The rotational hydrodynamics of nanoparticles is measured and considered under the influence of magnetic shape anisotropy in the framework of the Stoner-Wohlfarth theory. The plasmon-optical properties are explained by discrete-dipole finite-element simulations. Rotational dynamical measurements of imprinted nanoprobes for two test proteins demonstrate the applicability as highly sensitive biomolecular nanoprobes.

scholarly journals Highly Sensitive D-Shaped Plasmonic Refractive Index Sensor for a Broad Range of Refractive Index Detection

2021 ◽  
Vol 13 (1) ◽  
pp. 1-11
Author(s):  
Emranul Haque ◽  
Abdullah Al Noman ◽  
Md. Anwar Hossain ◽  
Nguyen Hoang Hai ◽  
Yoshinori Namihira ◽  
...  
Keyword(s):  
Refractive Index ◽  
Refractive Index Sensor ◽  
Highly Sensitive ◽  
Refractive Index Detection
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