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.

High-sensitivity silicon-based photonic crystal refractive index biosensor based on defect-mode coupling

2018 ◽  
Vol 427 ◽  
pp. 409-417 ◽  
Author(s):  
Chao Wu ◽  
Xing Liu ◽  
Shuai Feng ◽  
Xiao Chen ◽  
Chuanbo Li ◽  
...  
Keyword(s):  
Refractive Index ◽  
Photonic Crystal ◽  
Mode Coupling ◽  
Defect Mode ◽  
High Sensitivity ◽  
Silicon Based

scholarly journals Hybrid Grating in Reduced-Diameter Fiber for Temperature-Calibrated High-Sensitivity Refractive Index Sensing

2019 ◽  
Vol 9 (9) ◽  
pp. 1923
Author(s):  
Biqiang Jiang ◽  
Zhen Hao ◽  
Dingyi Feng ◽  
Kaiming Zhou ◽  
Lin Zhang ◽  
...  
Keyword(s):  
Refractive Index ◽  
Simultaneous Measurement ◽  
Surrounding Medium ◽  
High Sensitivity ◽  
Fiber Grating ◽  
Bragg Resonance ◽  
Core Mode ◽  
Promising Alternative ◽  
Sensing Applications ◽  
Highly Sensitive

We propose and experimentally demonstrate a hybrid grating, in which an excessively tilted fiber grating (Ex-TFG) and a fiber Bragg grating (FBG) were co-inscribed in a reduced-diameter fiber (RDF). The hybrid grating showed strong resonances due to coupling among core mode and a set of polarization-dependent cladding modes. This coupling showed enhanced evanescent fields by the reduced cladding size, thus allowing stronger interaction with the surrounding medium. Moreover, the FBG’s Bragg resonance confined by the thick cladding was exempt from the change of the surrounding medium’s refractive index (RI), and then the FBG can work as a temperature compensator. As a result, the Ex-TFG in RDF promised a highly sensitive RI measurement, with a sensitivity up to ~1224 nm/RIU near the RI of 1.38. Through simultaneous measurement of temperature and RI, the temperature dependence of water’s RI is then determined. Therefore, the proposed hybrid grating with a spectrum of multi-peaks embedded with a sharp Bragg resonance is a promising alternative for the simultaneous measurement of multi-parameters for many RI-based sensing applications.

scholarly journals High-Sensitivity Terahertz Refractive Index Sensor in a Multilayered Structure with Graphene

Nanomaterials ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 500 ◽  
Author(s):  
Jiao Tang ◽  
Yunyang Ye ◽  
Jiao Xu ◽  
Zhiwei Zheng ◽  
Xiangliang Jin ◽  
...  
Keyword(s):  
Refractive Index ◽  
High Sensitivity ◽  
Multilayered Structure ◽  
Monolayer Graphene ◽  
Refractive Index Sensor ◽  
Optical Resonance ◽  
Graphene Layers ◽  
Terahertz Band ◽  
Highly Sensitive ◽  
Terahertz Frequencies

In this paper, we propose a high-sensitivity optical sensor at terahertz frequencies based on a composite structure containing a one-dimensional photonic crystal (1D PC) coated with a layer of monolayer graphene. Between the 1D PC and the graphene there is a sensing medium. This high-sensitivity phenomenon originates from the excitation of optical resonance between the graphene and the 1D PC. The proposed sensor is highly sensitive to the Fermi energy of graphene, the thickness and refractive index of the sensing medium, and the number of graphene layers. By selecting appropriate parameters, the maximum sensitivity ( 407.36 ∘ / RIU ) is obtained. We believe the proposed configuration is promising for fabricating graphene-based biosensor- or gas-sensor devices and other related applications in the terahertz band.

Highly Sensitive THz Refractive Index Sensor Based on Folded Split-Ring Metamaterial Graphene Resonators

2021 ◽  
Author(s):  
Mohammad-Reza Nickpay ◽  
Mohammad Danaie ◽  
Ali Shahzadi
Keyword(s):  
Refractive Index ◽  
Biomedical Application ◽  
High Sensitivity ◽  
Peak Frequency ◽  
Refractive Index Sensor ◽  
Split Ring ◽  
Perfect Absorption ◽  
Sensing Applications ◽  
Highly Sensitive ◽  
Dc Bias

Abstract A highly sensitive absorption-based sensor based on folded split-ring metamaterial graphene resonators (FSRMGRs) is designed, and its biomedical application in terahertz (THz) spectrum is investigated. The sensor has a nearly perfect absorption with a spectral absorption coefficient of 99.75% at 4 THz, with a high Q-factor (average) of 13.76. The resonance peak frequency is sensitive to the refractive index (RI) of the test medium (analyte) and a fairly high sensitivity of 851 GHz/RIU has been obtained. The specifications of the sensor can be tuned by an external DC-bias voltage applied to the graphene layer. According to the obtained results, the developed absorber appears to be a good candidate bio-sensing applications.

Temperature-Insensitive Miniaturized Fiber Inline Fabry-Perot Interferometer Fabricated by Femtosecond Laser

2008 ◽  
Author(s):  
Yukun Han ◽  
Cheng-Hsiang Lin ◽  
Hai-Lung Tsai ◽  
Tao Wei ◽  
Hai Xiao
Keyword(s):  
Refractive Index ◽  
Refractive Index Change ◽  
High Sensitivity ◽  
Temperature Dependent ◽  
Refractive Index Measurement ◽  
Index Measurement ◽  
Highly Sensitive ◽  
Fabry Perot ◽  
Fs Laser ◽  
One Step

This article presents a miniaturized fiber inline Fabry-Perot interferometer (FPI), with an open micro-notch cavity fabricated by one-step femtosecond (fs) laser micromachining, for highly sensitive refractive index measurement. The device was tested for measurement of the refractive indices of various liquids including isopropanol, acetone and methanol at room temperature, as well as the temperature-dependent refractive index of deionized water from 3 to 90°C. The sensitivity for measurement of refractive index change of water was 1163 nm/RIU at the wavelength of 1550 nm. The temperature cross-sensitivity of the device was about 1.1×10−6 RIU/°C. The small size, all-fiber structure, small temperature dependence, linear response and high sensitivity, make the device attractive for chemical and biological sensing.

Splitting and Filtering Properties of Defect-Mode in One-Dimensional Photonic Crystal

2013 ◽  
Vol 760-762 ◽  
pp. 378-382
Author(s):  
Jian Kun Peng ◽  
Yan Ling Han ◽  
Hong Wang
Keyword(s):  
Refractive Index ◽  
Photonic Crystal ◽  
Mode Coupling ◽  
Incident Angle ◽  
Defect Mode ◽  
Defect Modes ◽  
One Dimensional ◽  
Mode Split ◽  
Spacing Interval ◽  
Coupling Mode

By the Transfer Matrix Method (TMM), the properties of defect modes, such as splitting, coupling and filtering, have been researched in detail. The influence of refractive index and incident angle on the defect-mode coupling has been investigated. Simulating results exhibit that coupling mode split as two defect modes when they are close to each other. This property is closely related to the refractive index and the spacing interval between defect layers. The incident angle can reach 30 degree, which has a potential application in full angle filtering.

scholarly journals Tapered Fiber-Optic Mach-Zehnder Interferometer for Ultra-High Sensitivity Measurement of Refractive Index

Sensors ◽  
2019 ◽  
Vol 19 (7) ◽  
pp. 1652 ◽  
Author(s):  
Vahid Ahsani ◽  
Farid Ahmed ◽  
Martin Jun ◽  
Colin Bradley
Keyword(s):  
Refractive Index ◽  
Fiber Optic ◽  
High Sensitivity ◽  
Single Mode ◽  
Single Mode Fiber ◽  
Zehnder Interferometer ◽  
Sensitivity Measurement ◽  
Biochemical Sensing ◽  
Highly Sensitive ◽  
Mach Zehnder Interferometer

A Mach-Zehnder interferometer (MZI) based fiberoptic refractive index (RI) sensor is constructed by uniformly tapering standard single mode fiber (SMF) for RI measurement. A custom flame-based tapering machine is used to fabricate microfiber MZI sensors directly from SMFs. The fabricated MZI device does not require any splicing of fibers and shows excellent RI sensitivity. The sensor with a cladding diameter of 35.5 µm and length of 20 mm exhibits RI sensitivity of 415 nm/RIU for RI range of 1.332 to 1.384, 1103 nm/RIU for RI range of 1.384 to 1.4204 and 4234 nm/RIU for RI range of 1.4204 to 1.4408, respectively. The sensor reveals a temperature sensitivity of 0.0097 nm/°C, which is relatively low in comparison to its ultra-high RI sensitivity. The proposed inexpensive and highly sensitive optical fiber RI sensors have numerous applications in chemical and biochemical sensing fields.

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 Highly sensitive refractive index sensor based on SPR with silver and titanium dioxide coating

2021 ◽  
Author(s):  
haiming yang ◽  
Guangyao Wang ◽  
Ying Lu ◽  
Jianquan Yao
Keyword(s):  
Refractive Index ◽  
Titanium Dioxide ◽  
Near Infrared ◽  
High Sensitivity ◽  
Organic Chemical ◽  
Refractive Index Sensor ◽  
Geometrical Parameters ◽  
Crystal Fiber ◽  
Wavelength Sensitivity ◽  
Highly Sensitive

Abstract A surface plasmon resonance (SPR) sensor based on dual-layered air hole shaped photonic crystal fiber (PCF) is proposed to realize the simultaneous measurement of refractive index (RI). The plasma materials silver (Ag) and titanium dioxide (TiO2) were sequentially coated on the outer surface of PCF to obtain enhanced sensing properties. By carefully adjusting the geometrical parameters, the simulation results show a maximum wavelength sensitivity of 72000 nm/RIU for analyte refractive indices ranging from 1.26 to 1.365, which realizes the high-sensitivity sensing in the visible to near-infrared optical band. Moreover, the sensor attains a maximum figure of merit (FOM) of 229 and RI resolution of 1.29 × 10− 6. This work shows great potential for real-time, affordable, and accurate measurement in biomedical, biological and organic chemical domains.

High-sensitivity detection of gold labels by high-angle dark-field STEM imaging

1990 ◽  
Vol 48 (3) ◽  
pp. 892-893 ◽  
Author(s):  
Max T. Otten
Keyword(s):  
High Sensitivity ◽  
Dark Field ◽  
Bright Field ◽  
Backscattered Electron Imaging ◽  
Backscattered Electrons ◽  
Average Atomic Number ◽  
Highly Sensitive ◽  
Backscattered Electron ◽  
Electron Imaging ◽  
High Sensitivity Detection

Labelling of antibodies with small gold probes is a highly sensitive technique for detecting specific molecules in biological tissue. Larger gold probes are usually well visible in TEM or STEM Bright-Field images of unstained specimens. In stained specimens, however, the contrast of the stain is frequently the same as that of the gold labels, making it virtually impossible to identify the labels, especially when smaller gold labels are used to increase the sensitivity of the immunolabelling technique. TEM or STEM Dark-Field images fare no better (Figs. 1a and 2a), again because of the absence of a clear contrast difference between gold labels and stain.Potentially much more useful is backscattered-electron imaging, since this will show differences in average atomic number which are sufficiently large between the metallic gold and the stains normally used. However, for the thin specimens and at high accelerating voltages of the STEM, the yield of backscattered electrons is very small, resulting in a very weak signal. Consequently, the backscattered-electron signal is often too noisy for detecting small labels, even for large spot sizes.

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