scholarly journals Refractive index sensing with Fano resonances in silicon oligomers

2017 ◽  
Vol 375 (2090) ◽  
pp. 20160070 ◽  
Author(s):  
Katie E. Chong ◽  
Henry W. Orton ◽  
Isabelle Staude ◽  
Manuel Decker ◽  
Andrey E. Miroshnichenko ◽  
...  
Keyword(s):  
Refractive Index ◽  
Figure Of Merit ◽  
Spectral Features ◽  
Fano Resonances ◽  
Refractive Index Sensitivity ◽  
New Horizons ◽  
Refractive Index Sensing ◽  
Index Sensitivity

We demonstrate experimentally refractive index sensing with localized Fano resonances in silicon oligomers, consisting of six disks surrounding a central one of slightly different diameter. Owing to the low absorption and narrow Fano-resonant spectral features appearing as a result of the interference of the modes of the outer and the central disks, we demonstrate refractive index sensitivity of more than 150 nm RIU −1 with a figure of merit of 3.8. This article is part of the themed issue ‘New horizons for nanophotonics’.

scholarly journals Optical Waveguides with Compound Multiperiodic Grating Nanostructures for Refractive Index Sensing

2016 ◽  
Vol 2016 ◽  
pp. 1-11 ◽  
Author(s):  
Lars Thorben Neustock ◽  
Sabrina Jahns ◽  
Jost Adam ◽  
Martina Gerken
Keyword(s):  
Refractive Index ◽  
Optical Waveguides ◽  
Spectral Characteristics ◽  
Quality Factors ◽  
Refractive Index Sensitivity ◽  
Refractive Index Sensing ◽  
Guided Mode ◽  
Duty Cycles ◽  
Rigorous Coupled Wave ◽  
Index Sensitivity

The spectral characteristics and refractive index sensitivity of compound multiperiodic grating waveguides are investigated in theory and experiment. Compound gratings are formed by superposition of two or more monoperiodic gratings. Compared to monoperiodic photonic crystal waveguides, compound grating waveguides offer more degrees of design freedom by choice of component grating periods and duty cycles. Refractive index sensing is achieved by evaluating the wavelength or intensity of guided mode resonances in the reflection spectrum. We designed, fabricated, and characterized 24 different compound multiperiodic nanostructured waveguides for refractive index sensing. Simulations are carried out with the Rigorous Coupled Wave Algorithm (RCWA). The resulting spectra, resonance sensitivities, and quality factors are compared to monoperiodic as well as to three selected aperiodic nanostructures (Rudin-Shapiro, Fibonacci, and Thue-Morse). The refractive index sensitivity of the TE resonances is similar for all types of investigated nanostructures. For the TM resonances the compound multiperiodic nanostructures exhibit higher sensitivity values compared to the monoperiodic nanostructure and similar values as the aperiodic nanostructures. No significant influence of the compound grating duty cycles on the sensitivity is observed.

scholarly journals Tunable Fano Resonances in an Ultra-Small Gap

2020 ◽  
Vol 10 (7) ◽  
pp. 2603
Author(s):  
Fuqiang Yao ◽  
Fang Li ◽  
Zhicong He ◽  
Yahui Liu ◽  
Litu Xu ◽  
...  
Keyword(s):  
Refractive Index ◽  
High Performance ◽  
Figure Of Merit ◽  
Silver Film ◽  
Destructive Interference ◽  
Refractive Index Sensitivity ◽  
Thin Aluminum ◽  
Index Sensitivity ◽  
Index Unit ◽  
Dielectric Environment

A Fano resonance is experimentally observed in a single silver nanocube separated from a supporting silver film by a thin aluminum oxide film. The resonance spectrum is modulated by changing the size of the silver nanocube and its distance from the silver film. The system is fabricated by a bottom-up process with an accurately controlled nanogap at the sub-6-nm scale. The simulation result shows that the destructive interference between the dipole mode and the quadrupole mode in this “nanocube on mirror” (NCoM) structure is responsible for the resonance. The spectra red-shifted as the size of the silver nanocube increased and its distance from the silver film decreased. In addition, a refractive index sensitivity of the spectrum of 140 meV/RIU (refractive index unit), with a 2.4 figure of merit, is obtained by changing the dielectric environment around the silver nanocube. This work will enable the development of high-performance tunable optical nanodevices based on NCoM structures.

Fano Resonances in Thin Metallic Grating for Refractive Index Sensing with High Figure of Merit

Plasmonics ◽  
2015 ◽  
Vol 11 (1) ◽  
pp. 139-149 ◽  
Author(s):  
Lixia Li ◽  
Yuzhang Liang ◽  
Mengdi Lu ◽  
Wei Peng
Keyword(s):  
Refractive Index ◽  
Figure Of Merit ◽  
Fano Resonances ◽  
Metallic Grating ◽  
Refractive Index Sensing ◽  
High Figure

scholarly journals Analysis of Scaling Law and Figure of Merit of Fiber-Based Biosensor

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Jui-Teng Lin ◽  
Da-Chuan Cheng ◽  
Minshan Jiang ◽  
Yueh-Sheng Chiang ◽  
Hsia-Wei Liu
Keyword(s):  
Refractive Index ◽  
Aspect Ratio ◽  
Figure Of Merit ◽  
Scaling Laws ◽  
Scaling Law ◽  
Optimal Designs ◽  
Plasmon Excitation ◽  
Refractive Index Sensitivity ◽  
Optimal Value ◽  
Index Sensitivity

This paper presents a normalized transmitted signal (NTS) of a fiber-based sensor using gold nanorods as the plasmon excitation medium of the evanescent wave. The NTS and the refractive index (RI) sensitivity is calculated as a function of the gold aspect ratio (R), the RI of the sensing medium, and a scaling parameter given by the ratio of the fiber length and its diameter. Finally, the optimal value of gold aspect ratio is calculated to beR= (3.0–4.0) for maximum figure of merits (FOMs) defined by the ratio of the refractive index sensitivity and the full width at half maximum. The scaling laws and the FOM presented in this paper may serve as the guidelines for optimal designs in fiber-based nanosensors.

scholarly journals Improved Refractive Index Sensitivity Utilizing Long-Period Gratings with Periodic Corrugations on Cladding

2012 ◽  
Vol 2012 ◽  
pp. 1-5 ◽  
Author(s):  
Anthony Lim ◽  
Wen Bin Ji ◽  
Swee Chuan Tjin
Keyword(s):  
Refractive Index ◽  
Cost Effective ◽  
Experimental Results ◽  
Refractive Index Sensitivity ◽  
Long Period ◽  
Specimen Collection ◽  
Long Period Gratings ◽  
Highly Sensitive ◽  
Index Sensitivity

A new structure of Long-Period Gratings (LPGs) sensor is introduced as a sensitive ambient RI sensor. This structure consists of creating periodic corrugations on the cladding of the LPG. The experimental results show that this LPG structure has good performances in terms of linearity and sensitivity and serves as a highly sensitive and cost-effective sensor. It also has the advantage of portability as the corrugation can also serve as the reservoir for the specimen collection to be tested.

scholarly journals Analysis of Effects of Surface Roughness on Sensing Performance of Surface Plasmon Resonance Detection for Refractive Index Sensing Application

Sensors ◽  
2021 ◽  
Vol 21 (18) ◽  
pp. 6164
Author(s):  
Treesukon Treebupachatsakul ◽  
Siratchakrit Shinnakerdchoke ◽  
Suejit Pechprasarn
Keyword(s):  
Surface Roughness ◽  
Refractive Index ◽  
Surface Plasmon Resonance ◽  
Surface Plasmon ◽  
Plasmon Resonance ◽  
Figure Of Merit ◽  
Root Mean Square Roughness ◽  
Performance Parameters ◽  
Refractive Index Sensing ◽  
Sensing Performance

This paper provides a theoretical framework to analyze and quantify roughness effects on sensing performance parameters of surface plasmon resonance measurements. Rigorous coupled-wave analysis and the Monte Carlo method were applied to compute plasmonic reflectance spectra for different surface roughness profiles. The rough surfaces were generated using the low pass frequency filtering method. Different coating and surface treatments and their reported root-mean-square roughness in the literature were extracted and investigated in this study to calculate the refractive index sensing performance parameters, including sensitivity, full width at half maximum, plasmonic dip intensity, plasmonic dip position, and figure of merit. Here, we propose a figure-of-merit equation considering optical intensity contrast and signal-to-noise ratio. The proposed figure-of-merit equation could predict a similar refractive index sensing performance compared to experimental results reported in the literature. The surface roughness height strongly affected all the performance parameters, resulting in a degraded figure of merit for surface plasmon resonance measurement.

scholarly journals Improve the Hole Size-dependent Refractive Index Sensitivity  of Au-Ag Nanocages by Tuning the Alloy Composition

2021 ◽  
Author(s):  
Jianjun LI ◽  
Qiu-Xiang Qin ◽  
Guo-Jun Weng ◽  
Jian Zhu ◽  
Jun-Wu Zhao
Keyword(s):  
Dielectric Constant ◽  
Refractive Index ◽  
Electric Field ◽  
Alloy Composition ◽  
Geometric Parameters ◽  
Sensitivity Factor ◽  
Hole Size ◽  
Refractive Index Sensitivity ◽  
Electric Field Direction ◽  
Index Sensitivity

Abstract In this study, the nanoboxes is converted into Au-Ag alloy nanocages by increasing the hole size. Discrete dipole approximation (DDA) is used to study the extinction spectrum and the refractive index sensing characteristics of Au-Ag alloy nanocages with different geometric parameters. With the increase of Au component, the local surface plasmon resonance (LSPR) peak shows approximately linear redshift and the sensitivity factor shows approximately linear decrease. The refractive index sensitivity can be effectively controlled by the Au-Ag ratio at large hole size because the hole and cavity surfaces distribute more environmental dielectric components. Therefore, increasing the hole size and decreasing the Au-Ag ratio can improve the refractive index sensitivity. To explain the effect of alloy composition on the LSPR characteristics and the refractive index sensitivity, the local electric field distributions with different geometric parameters are plotted. We find that the electric field direction on the hole and cavity surfaces are controlled by the Au-Ag ratio and environmental dielectric constant. Moreover, the field vector on the hole and cavity surfaces are formed by the superposition of the incident field, the electric field generated by the oscillating electrons on the outer surface, and the polarized field in the environmental dielectric constant.

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