High-performance Plasmonic Sensor Research Articles

Four-state Fano resonance electro-optical modulator and sensor based on double borophene-dielectric grating structure

In this paper, we propose a borophene-based double-dielectric-grating structure (BDDGS) to realize the Fano resonance electro-optical modulator and sensor. The Fano resonance originated from the coupling of two resonance modes excited by the upper borophene grating (UBG) and the lower borophene grating (LBG). The coupling mode theory (CMT) is utilized to fit the Fano transmission spectrum. The calculated result fits well with the simulated spectrum. We found the Fano resonance wavelengths exhibit a blue shift with increasing the carrier density of the borophene layer. Further, we utilize this property to achieve a Four-state Fano resonance electro-optical modulator. The working wavelengths of the ON-ON (11), ON–OFF (10), OFF–ON (01), and OFF-OFF (00) states are 1.321 μm and 1.676 μm, respectively. The asymmetric Fano spectra exhibit high sensing sensitivity S=21THz/RIU and figure of merit FOM=3.9RIU−1. Moreover, our proposed structure possesses a slow-fast light effect with the maximum group index are 57.84 and −332.3, respectively. Although several Fano resonance and electro-optical modulators based on two- dimensional (2D) material, like graphene, black phosphorus, and transition metal dichalcogenides (TMDs) are previously reported, this paper designed a borophene-based metamaterial to achieve Fano resonance electro-optical modulator and sensor, because borophene possesses a series of excellent physical and chemical properties, for example, mechanical compliance, high carrier mobility, and optical transparency. Therefore, the proposed borophene-based metamaterial will be beneficial in the fields of high-performance plasmonic sensors, slow light, and electro-optical modulators in the near future.

Fano resonance based on a triangular resonator and its application on nanosensing

Fano resonance sensors based on metal–insulator–metal (MIM) waveguide have potential applications in fields such as biology, chemistry, and the environment. Here, a nanosensor based on Fano resonance in an MIM-based isosceles triangular resonator system is proposed and numerically studied by finite element method. Simulation results show that the Fano peak can be easily tuned by adjusting the scale factor and the refractive index within the resonator. Furthermore, we thoroughly analyze the impact of the apex angle, rotation angle, and vertical displacement of the resonator on the transmission spectrum. Finally, the sensing characteristics of the proposed structure are optimized and analyzed, and a high-performance plasmonic sensor with a sensitivity of 1100[Formula: see text]nm/RIU and the maximum figure of merit of [Formula: see text] is obtained. The distinctive attributes of our suggested structure are applicable in the realization of various integrated components for the development of multifunctional high-performance nanophotonics devices.

High-Performance Plasmonic Sensor for Detection of Cortisol Biomarker in Near Infrared With Photonic Spin Hall Effect

High-Performance Plasmonic Sensor for Detection of Cortisol Biomarker in Near Infrared With Photonic Spin Hall Effect

High-Performance Plasmonic Sensor Based on Silver, Gold and Graphene Layers for Cancer Cell Detection at 632.8 nm Wavelength with Photonic Spin Hall Effect

High-Performance Plasmonic Sensor Based on Silver, Gold and Graphene Layers for Cancer Cell Detection at 632.8 nm Wavelength with Photonic Spin Hall Effect

Rational Fabrication of Ag Nanocone Arrays Embedded with Ag NPs and Their Sensing Applications.

Colloidal lithography is used to design and construct a high-performance plasmonic sensor based on Ag nanocone arrays embedded with Ag NPs. The surface plasmon polariton (SPP) of the Ag nanocone array and the localized surface plasmon resonance (LSPR) of Ag NPs inside the nanocones can both couple incident photons. Sharp reflectance troughs are considerably enhanced by coupling the SPPs and LSPR, which is made possible by carefully tuning the nanocone sizes. To maximize the line shape and sensitivity, other geometric factors, such as the thickness of the silver layer and the size of the Ag NPs, are modified. Finite-difference time-domain computations confirm these hypotheses and experimental findings. We use well-researched solvents with various refractive indices as a model system to demonstrate good sensing performance as a proof of concept. The crystal used in this investigation has the ideal refractive index sensitivity, having 500 nm lattice constant, 350 nm nanocone height, and 350 nm base diameter (aspect ratio = 1). The Ag nanocone array embedded with Ag NPs is a good contender for a sensing platform due to its compact structure and efficient read-out apparatus.

Plasmonic Sensor and Surface Enhanced Fluorescence Imaging Based on Hollow Nanocone Arrays

Hollow nanocone arrays are fabricated by a low-cost and efficient colloidal lithography (CL) technique. The hollow nanocone arrays are then reversed to make only the tips contact the substrate. The optical properties of the obverse and inverse hollow nanocone arrays are determined by the surrounding environment, showing different reflection spectra and structure dependence. The inverse hollow nanocone arrays show a relative index sensitivity of 70% per RIU with strict linearity. The fluorescence of fluorophore or staining cells can be facilely enhanced by placing them on the tips of the hollow nanocone arrays, while having no quenching effect. The study of the obverse and inverse hollow nanocone arrays can benefit the understanding of the effect of the environment on the plasmonic resonances. The hollow nanocone arrays are promising to serve as high-performance plasmonic sensors and versatile substrates for surface-enhanced fluorescence imaging.

High-performance plasmonic sensor based on photonic crystal fiber for refractive index and temperature sensing

In this paper, a refractive index and temperature plasmonic sensor based on photonic crystal fiber is proposed. In order to achieve the best performance, a serial of study on the theory and experimental steps is carried out, including simulation calculation, detection system, coating method and chemical etch technology. Experimental results demonstrate that a high average sensitivity of 3381 nm/RIU within a linear refractive index ranging from 1.3333 to 1.3860 can be achieved, which is greater than the traditional fiber structure. In addition, this sensor is helpful to measure temperature change and the sensitivity could be 2 nm/°C. Due to its easy and controllable fabrication, the proposed sensor has great application prospects in the field of optical device.

High-performance plasmonic oblique sensors for the detection of ions

Efficient optical sensing is desirable for a wide range of applications. For sensors, the spectral factors of the sensitivity (S) and the figure of merit (FoM) and the intensity change related figure of merit (FOM*) are all the key factors in sensing measurement. In this work, we propose and demonstrate a novel high-performance plasmonic sensor platform using a resonant cavity array grating under oblique excitation. An ultra-sharp absorption mode with a bandwidth down to 1.3 nm is achieved when the oblique angle is 7.5°. During the sensing of the Na+ (Cl−) ions in the solution, the spectral S and FoM factors reach 568 nm RIU−1 (refractive index unit) and 436 nm RIU−1, respectively. The minimum detection limit is as low as 3.521 × 10–6 RIU. The FOM* factor is simultaneously up to 907. Moreover, the spectral intensity change is up to 57% when only a 1% concentration change is introduced into the solution. The detection limit of the concentration of the ions can be as low as 0.002%. The sensor has great potential applications due to its ultrahigh S, FoM, and FOM*.

Thermal deformation of gold nanostructures and its influence on surface plasmon resonance sensing.

Plasmonic nanostructures have been recently used in elevated temperature applications such as sensing of high-energy systems and localized heat generation for heat-assisted magnetic recording, thermophotovaltaics, and photothermal therapy. However, plasmonic nanostructures exposed to elevated temperature often experience permanent deformations, which could significantly degrade performance of the plasmonic devices. Therefore, understanding of thermal deformation of plasmonic nanostructures and its influence on the device performance is essential to the development of robust high-performance plasmonic devices. Here, we report thermal deformation of lithographic planar gold nanopatch and nanohole arrays and its influence on surface plasmon resonance sensing. The gold nanostructures are fabricated on a silicon substrate and on the end-face of an optical fiber using electron-beam lithography and focused-ion-beam lithography, respectively. The fabricated gold nanostructures are exposed to cyclic thermal loading in the range of 25 °C to 500 °C. Through experimental and numerical studies, we investigate (i) thermal deformation modes of the gold nanostructures, (ii) influence of the gold nanostructure geometry on the degree and mechanism of the thermal deformation, and (iii) influence of the thermal deformation on performance of surface plasmon resonance sensing. The obtained understanding from these studies is expected to help guide the development of robust high-performance plasmonic sensors for monitoring in elevated temperature environments. Although the current work is focused on gold nanostructures, it can be extended to provide useful insights on thermal deformation of refractory plasmonic nanostructures at extreme temperature.

A High Performance Plasmonic Sensor Based on Metal-Insulator-Metal Waveguide Coupled with a Double-Cavity Structure

A high performance plasmonic sensor based on a metal-insulator-metal (MIM) waveguide coupled with a double-cavity structure consisting of a side-coupled rectangular cavity and a disk cavity is proposed. The transmission characteristics of the rectangular cavity and disk cavity are analyzed theoretically and the improvements of performance for the double-cavity structure compared with a single cavity are studied. The influence of structural parameters on the transmission spectra and sensing performance are investigated in detail. A sensitivity of 1136 nm/RIU with a high figure of merit of 51,275 can be achieved at the resonant wavelength of 1148.5 nm. Due to the high performance and easy fabrication, the proposed structure may be applied in integrated optical circuits and on-chip nanosensors.

Optical Sensitivity Gain in Silica-Coated Plasmonic Nanostructures.

Ultrathin films of silica realized by sol-gel synthesis and dip-coating techniques were successfully applied to predefined metal/polymer plasmonic nanostructures to spectrally tune their resonance modes and to increase their sensitivity to local refractive index changes. Plasmon resonance spectral shifts up to 100 nm with slope efficiencies of ∼8 nm/nm for increasing layer thickness were attained. In the ultrathin layer regime (<10 nm), which could be reached by suitable dilution of the silica precursors and optimization of the deposition speed, the sensitivity of the main plasmonic resonance to refractive index changes in aqueous solution could be increased by over 50% with respect to the bare plasmonic chip. Numerical simulations supported experimental data and unveiled the mechanism responsible for the optical sensitivity gain, proving an effective tool in the design of high-performance plasmonic sensors.

Detection of Formaldehyde in Water: A Shape-Effect on the Plasmonic Sensing Properties of the Gold Nanoparticles

The effect of morphology on the plasmonic sensing of the presence of formaldehyde in water by gold nanostructures has been investigated. The gold nanostructures with two different morphologies, namely spherical and rod, were prepared using a seed-mediated method. In typical results, it was found that the plasmonic properties of gold nanostructures were very sensitive to the presence of formaldehyde in their surrounding medium by showing the change in both the plasmonic peaks position and the intensity. Spherical nanoparticles (GNS), for example, indicated an increase in the sensitivity when the size was increased from 25 to 35 nm and dramatically decreased when the size was further increased. An m value, the ratio between plasmonic peak shift and refractive index change, as high as 36.5 nm/RIU (refractive index unit) was obtained so far. An expanded sensing mode to FD was obtained when gold nanostructures with nanorods morphology (GNR) were used because of the presence of two plasmonic modes for response probing. However, in the present study, effective plasmonic peak shift was not observed due to the intense plasmonic coupling of closely packed nanorod structures on the surface. Nevertheless, the present results at least provide a potential strategy for response enhancement via shape-effects. High performance plasmonic sensors could be obtained if controlled arrays of nanorods can be prepared on the surface.

Elevated Ag nanohole arrays for high performance plasmonic sensors based on extraordinary optical transmission

Label-free molecular sensing is one of the most fascinating applications of recently fast developing plasmonics. However, the implementation of plasmonic sensors in modern analytical systems strongly demands high sensitivity. Herein, by combining colloidal lithography with subsequent isotropic chemical etching of an underlying glass substrate, we report the fabrication of elevated Ag nanohole arrays (EANAs) which exhibit the property of extraordinary optical transmission. Finite-difference time-domain calculations show that the optical properties of the EANAs behave as though floating above the substrate with no support whatsoever. Compared with the original Ag nanohole arrays directly attached to a glass substrate, the refractive index sensitivity of the EANAs increases to ∼648 nm/RIU from the original ∼252 nm/RIU. This greatly enhanced sensing performance makes the EANAs very attractive as a platform for plasmonic sensing systems. As a proof-of-concept, we corroborated these findings with the label-free detection of anti-human IgG using the as-prepared EANAs.