scholarly journals Refractometric Sensing with Periodic Nano-Indented Arrays: Effect of Structural Dimensions

Sensors ◽  
2019 ◽  
Vol 19 (4) ◽  
pp. 897 ◽  
Author(s):  
Daniel Carney ◽  
Halldor Svavarsson ◽  
Hafez Hemmati ◽  
Alexander Fannin ◽  
Jae Yoon ◽  
...  
Keyword(s):  
Refractive Index ◽  
Spectral Response ◽  
Normal Incidence ◽  
Interference Lithography ◽  
Sensor Element ◽  
Refractive Index Sensitivity ◽  
Plasmonic Sensors ◽  
Index Sensitivity ◽  
Geometrical Dimensions ◽  
Index Unit

Fabrication and sensor application of a simple plasmonic structure is described in this paper. The sensor element consists of nano-patterned gold film brought about from two-dimensional periodic photoresist templates created by holographic laser interference lithography. Reflectance spectroscopy revealed that the sensor exhibits significant refractive index sensitivity. A linear relationship between shifts in plasmonic resonances and changes in the refractive index were demonstrated. The sensor has a bulk sensitivity (SB) of 880 nm/refractive index unit and work under normal incidence conditions. This sensitivity exceeded that of many common types of plasmonic sensors with more intricate structures. A modeled spectral response was used to study the effect of its geometrical dimensions on plasmonic behavior. A qualitative agreement between the experimental spectra and modeled ones was obtained.

scholarly journals A High-Birefringence Microfiber Sagnac-Interferometer Biosensor Based on the Vernier Effect

Sensors ◽  
2018 ◽  
Vol 18 (12) ◽  
pp. 4114 ◽  
Author(s):  
Xue-Zhou Wang ◽  
Qi Wang
Keyword(s):  
Refractive Index ◽  
Sagnac Interferometer ◽  
Refractive Index Sensitivity ◽  
Electrostatic Adsorption ◽  
High Birefringence ◽  
Polarization Maintaining Fiber ◽  
Good Biocompatibility ◽  
Polarization Maintaining ◽  
Index Sensitivity ◽  
Index Unit

We propose a high-sensitive Sagnac-interferometer biosensor based on theVernier effect (VE) with a high-birefringence microfiber. The sensitivity enhancement is achieved by utilizing two cascaded Sagnac interferometers. One of the two interference loops consists of a panda polarization-maintaining fiber as a filter, whilst the other is comprised of high-birefringent microfiber coated Graphene oxide (GO) as a sensing channel. We theoretically analyzed the sensitivity of the sensor and verified it with experiments. The results of the simulation show that the refractive index sensitivity is more than five times that of the fiber sensor based on a single Sagnac loop. The sensitivity of the refractive index in the experiments can reach 2429 nm/refractive index unit (RIU), which is basically in accordance with the simulation. We also use electrostatic adsorption to coat GO on the surface of the sensing channel. GO is employed to adsorb bovine serum albumin (BSA) molecules to achieve the desired detection results, which has good biocompatibility and large specific surface area. The sensitivity to detect BSA can reach 9.097 nm/(mg×mL−1).

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.

scholarly journals Birefringent Bragg Grating in C-Shaped Optical Fiber as a Temperature-Insensitive Refractometer

Sensors ◽  
2018 ◽  
Vol 18 (10) ◽  
pp. 3285 ◽  
Author(s):  
Rex Tan ◽  
Daryl Ho ◽  
Chun Tse ◽  
Yung Tan ◽  
Seong Yoo ◽  
...  
Keyword(s):  
Refractive Index ◽  
Optical Fiber ◽  
Ambient Temperature ◽  
Fiber Bragg Gratings ◽  
Temperature Fluctuations ◽  
Single Mode ◽  
Single Mode Fiber ◽  
Refractive Index Sensitivity ◽  
Index Sensitivity ◽  
Index Unit

We demonstrate a simple-to-fabricate refractometer based on the inscription of fiber Bragg gratings in a special C-shaped optical fiber. The C-shaped fiber was drawn into shape using a quarter cladding removed preform of a commercial standard single-mode fiber by simple machining. The sensor did not suffer from cross-sensitivity of the refractive index with ambient temperature fluctuations, commonly occurring with many optical fiber refractometers. A refractive index sensitivity of 1300 pm per refractive index unit (RIU) was achieved without employing any additional sensitization techniques such as tapering or etching.

Sensitive Near-Infrared Refractive Index Sensors Based on D-Shaped Photonic Crystal Fibers

2021 ◽  
Vol 21 (11) ◽  
pp. 5535-5541
Author(s):  
Thu Trang Hoang ◽  
Van Dai Pham ◽  
Thanh Son Pham ◽  
Khai Q. Le ◽  
Quang Minh Ngo
Keyword(s):  
Refractive Index ◽  
Photonic Crystal ◽  
Photonic Crystal Fiber ◽  
Near Infrared ◽  
Plasmonic Sensor ◽  
Refractive Index Sensitivity ◽  
Crystal Fiber ◽  
Refractive Index Sensors ◽  
Index Sensitivity ◽  
Index Unit

We report a numerical study of D-shaped photonic crystal fiber based plasmonic refractive index sensor with high resolution and sensitivity in the near-infrared region. D-shaped photonic crystal fiber is formed by side polishing one part of photonic crystal fiber. It has a polishing surface where plasmonic gold layer is coated to modulate the resonant wavelength and enhance the refractive index sensitivity. Several D-shaped photonic crystal fiber plasmonic sensors with various distances from the photonic crystal fiber’s core to the polishing surface and gold thicknesses are designed and their characteristics are analyzed by the finite element method. The simulation results indicate that distance from the photonic crystal fiber’s core to the polishing surface causes modifications in the loss intensity, the resonant wavelength, and the refractive index sensitivity of D-shaped photonic crystal fiber plasmonic sensor. Mass production of refractive index sensors were achieved using a simple fabrication process, whereby the D-shaped photonic crystal fiber is grinded where distance from the photonic crystal fiber’s core to the polishing surface is less than one layer thickness and then coated with the gold layer. For the refractive index sensing applications, the maxima theoretical resolution and sensitivity of D-shaped photonic crystal fiber plasmonic sensor reach 2.98 × 10 6refractive index unit and 6,140 nm/refractive index unit in range of 1.30–1.37, respectively. We also report an initial fabrication of the D-shaped photonic crystal fiber following the standard stack-and- draw method to demonstrate the feasibility of the proposed device by using our in-house equipments. The proposed D-shaped photonic crystal fiber plasmonic sensor design in this work would be useful for the development of cheap refractive index sensors with high sensitivity and resolution.

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 Enhanced Plasmonic Resonance Characteristics of AgNRs–Gold Film Hybrid System

2021 ◽  
Vol 8 ◽  
Author(s):  
Yanping Yin ◽  
Jin Zhu ◽  
Zaoji Wang ◽  
Guojun Ma ◽  
Huining Yuan ◽  
...  
Keyword(s):  
Refractive Index ◽  
Aspect Ratio ◽  
Gold Film ◽  
Spectral Response ◽  
Surrounding Medium ◽  
Resonance Wavelength ◽  
Spectral Shift ◽  
Refractive Index Sensor ◽  
Gap Size ◽  
Refractive Index Sensitivity

In recent years, the plasma gap resonance maintained by metal-film-coupled nanostructures has attracted extensive attention. This mainly originates from its flexible control of the spectral response and significantly enhanced field strength at the nanoparticle–film junction. In the present study, the tunability of local surface plasmon resonances (LSPRs) of nanorods coupled to a gold film is studied theoretically. To this end, the plasmonic resonances in the nanostructure of individual silver nanorod–gold film (AgNR-film) with different parameters are investigated. Obtained results show that the refractive index sensitivity (S) of nanostructures to the environment increases as the aspect ratio (Ar) of nanostructures increase. It is found that when the aspect ratio (Ar) is set to 3.5, the figure of merit (FOM) is the highest. Moreover, the variation in the gap distances of the nanorod monomer–gold film, electric field distribution of nanorods dimer, and the corresponding impact on the gold film are studied. It is concluded that the gap size of nanostructures has an exponential correlation with the resonance wavelength. Considering the remarkable influence of the gap size and the surrounding medium environment on the spectral shift of AgNR-film nanostructures, potential applications of the structure as a refractive index sensor and biomolecule measurement are proposed.

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.

Influence of diamond-like carbon overlay properties on refractive index sensitivity of nano-coated optical fibres

2013 ◽  
Vol 210 (10) ◽  
pp. 2100-2105 ◽  
Author(s):  
Mateusz Śmietana ◽  
Mariusz Dudek ◽  
Marcin Koba ◽  
Bartosz Michalak
Keyword(s):  
Refractive Index ◽  
Diamond Like Carbon ◽  
Optical Fibres ◽  
Refractive Index Sensitivity ◽  
Index Sensitivity
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