Leiming Wu

Sensitivity Improved SPR Biosensor Based on the MoS2/Graphene–Aluminum Hybrid Structure

MoS₂-graphene-based hybrid structures are biocompatible and useful in the field of biosensors. Herein, we propose a heterostructured MoS₂/aluminum (Al) film/MoS₂/graphene as a highly sensitive surface plasmon resonance (SPR) biosensor based on the Otto configuration. The sensitivity of the proposed biosensor is enhanced by using three methods. First, prisms of different refractive index have been discussed and it is found that sensitivity can be enhanced by using a low refractive index prism. Second, the influence of the thickness of the air layer on the sensitivity is analyzed and the optimal thickness of air is obtained. Finally, the sensitivity improvement and mechanism by using molybdenum disulfide (MoS₂)–graphene hybrid structure is revealed. The maximum sensitivity ∼ 190.83°/RIU is obtained with six layers of MoS₂ coating on both surfaces of Al thin film.

Manipulating the optical bistability at terahertz frequency in the Fabry-Perot cavity with graphene

We investigate theoretically the optical bistability from a Fabry-Perot cavity with graphene in the terahertz (THz) frequency. It is demonstrated that the optical bistablility in this cavity can be realized due to the electric field enhancement and the giant third-order nonlinear conductivity of graphene. The optical bistable behavior is strongly dependent on the transmission amplitude of the mirror and the position of the graphene in the cavity. It is especially important that the hysterical behaviors of the transmitted light rely on the optical conductivity of graphene, making the Fabry-Perot cavity to be a good candidate for dynamic tunable optical bistable device in the THz frequencies, owing to the possibility of high tunability of graphene conductivity by means of external electrostatic or magnetostatic field.

Absorption enhancement and total absorption in a graphene-waveguide hybrid structure

We propose a graphene/planar waveguide hybrid structure, and demonstrate total absorption in the visible wavelength range by means of attenuated total reflectance. The excitation of planar waveguide mode, which has strong near field enhancement and increased light interaction length with graphene, plays a vital role in total absorption. We analyze the origin and physical insight of total absorption theoretically by using an approximated reflectance, and show how to design such hybrid structure numerically. Utilizing the tunability of doped graphene, we discuss the possible application in optical modulators. We also achieve broadband absorption enhancement in near-IR range by cascading multiple graphene-waveguide hybrid structures. We believe our results will be useful not only for potential applications in optical devices, but also for studying other two-dimension materials.

Long-Range Surface Plasmon With Graphene for Enhancing the Sensitivity and Detection Accuracy of Biosensor

A novel long-range surface plasmon with graphene is proposed to enhance the sensitivity and detection accuracy (DA) of the biosensor. Compared with the conventional long-range surface plasmon resonance (LRSPR) structure with Au, the coating of the metal surface with graphene is employed to increase the biomolecules adsorption, prevent oxidation, and enhance the sensitivity and DA. Furthermore, we demonstrated that the sensitivity has a nearly tenfold improvement with a huge increasing DA in the proposed LRSPR biosensor compared with the SPR biosensor. Finally, we discuss the influence of the refractive index of sensing medium on the LRSPR biosensor and find that the sensitivity is changing with the refractive index of the sensing medium and that an optimal sensitivity can be obtained at a suitable refractive index. We believe that this scheme could find potential applications in chemical examination, medical diagnosis, and biological detection.

Tuning and Sensitivity Enhancement of Surface Plasmon Resonance Biosensor With Graphene Covered Au-MoS 2-Au Films

In the conventional surface plasmon resonance biosensor, the sensitivity using angular interrogation is low. Graphene/MoS2 has been attached on the metal surface to improve the sensitivity; however, the ability to improve sensitivity is limited. Here, by sandwiching the MoS2 sheets between two gold films in the Kretschmann configuration, we demonstrate an ultrasensitive surface plasmon resonance sensor. By optimizing the structure of sensor, we find that the sensitivity as high as 182°/RIU can be realized with 4-layers MoS2 and a monolayer graphene. Moreover, it is indicated that the sensitivity can be tuned and controlled by changing the layer numbers of graphene and MoS2.

Sensitivity Enhanced by MoS2–Graphene Hybrid Structure in Guided-Wave Surface Plasmon Resonance Biosensor

Compared with surface plasmon resonance (SPR) biosensor, guided-wave surface plasmon resonance (GWSPR) biosensor has a higher sensitivity. In order to further enhance the sensitivity of the GWSPR biosensor, the MoS2–graphene hybrid structure is proposed to cover on the surface of the thin silicon film. It is demonstrated that the sensitivity of the proposed biosensor configuration can be doubled by using optimized MoS2–graphene hybrid structure. By analyzing the electric field distributions with the proposed GWSPR biosensor, it is shown that the electric field intensity has a dramatic change with a slight change in refractive index of sensing medium, and it also means that the biosensor is sensitive to detect the analytes. Moreover, the proposed GWSPR biosensor has a wide detection range of refractive index of sensing medium, and the sensitivity is increased with the refractive index of sensing medium increasing.

High Sensitivity Intensity-Interrogated Bloch Surface Wave Biosensor With Graphene

Bloch surface wave (BSW) is a surface state excited within the truncate defect layer at the surface of a dielectric 1-D photonic crystal (1DPC), which has been suggested as an attractive alternative to surface plasmon resonance (SPR) in chemical and biological sensors. In this paper, we propose an intensity-sensitive BSW sensor based on the truncate 1DPC with graphene. By optimizing the thickness of the defect layer and the layer number of graphene, the maximum intensity sensitivity of biosensor can surpass

Ultrasensitive Terahertz Biosensors Based on Fano Resonance of a Graphene/Waveguide Hybrid Structure

3.5\times 10^{4}

An ultra-high sensitivity surface plasmon resonance sensor based on graphene-aluminum-graphene sandwich-like structure

/RIU, which is greater than that for the conventional BSW or SPR sensors. With such excellent and interesting performance, we believe that the structure can be useful for many important applications in the field of chemical and biological sensors in the future.

Improving the Performance of an SPR Biosensor Using Long-Range Surface Plasmon of Ga-Doped Zinc Oxide

Graphene terahertz (THz) surface plasmons provide hope for developing functional devices in the THz frequency. By coupling graphene surface plasmon polaritons (SPPs) and a planar waveguide (PWG) mode, Fano resonances are demonstrated to realize an ultrasensitive terahertz biosensor. By analyzing the dispersion relation of graphene SPPs and PWG, the tunable Fano resonances in the terahertz frequency are discussed. It is found that the asymmetric lineshape of Fano resonances can be manipulated by changing the Fermi level of graphene, and the influence of the thickness of coupling layer and air layer in sandwich structure on the Fano resonances is also discussed in detail. We then apply the proposed Fano resonance to realize the ultrasensitive terahertz biosensors, it is shown that the highest sensitivities of 3260 RIU−1 are realized. Our result is two orders of a conventional surface plasmon resonance sensor. Furthermore, we find that when sensing medium is in the vicinity of water in THz, the sensitivity increases with increasing refractive index of the sensing medium.