No abstract

No abstract

A theoretical study was conducted with the aim of improving the detection accuracy of graphene-based surface plasmon resonance (SPR) biosensors. We studied the effect of applying a bias voltage to the sensor surface on its detection accuracy. The optimum thicknesses of silver and gold layers in the biosensor of 47 nm and 3 nm, respectively, were determined. Graphene layers deposited on these thin silver and gold films formed a sensor surface system, on which the surface plasmons were excited. The real and imaginary parts of the refractive index of graphene were controlled by the bias voltage. When the chemical potential was increased from 36 meV to 8 eV, the detection accuracy of the sensor was correspondingly increased by 213%.

In this paper, a tunable absorber composed of asymmetric grating based on a graphene-dielectric-metal structure is proposed. The absorption of the absorber can be modified from 99.99% to 61.73% in the near-infrared by varying the Fermi energy of graphene, and the absorption wavelength can be tuned by varying the grating period. Furthermore, the influence of other geometrical parameters, the incident angle, and polarization are analyzed in detail by a finite-difference time-domain simulation. The graphene absorbers proposed in this paper have potential applications in the fields of stealth, sense, and photoelectric conversion. When the absorber that we propose is used as a gas sensor, the sensitivity of 200 nm/RIU with FOM can reach up to 159 RIU−1.

High-performance omnidirectional transmissive chromatic polarizers based on a one-dimensional dielectric-metal-dielectric subwavelength grating structure are proposed. The incident angle-insensitive properties, azimuthal angle-insensitive properties and polarization features are investigated thoroughly to realize the proposed omnidirectional transmissive chromatic polarizers. The color difference at different angles for the proposed yellow polarizers is less than 0.9746, and the extinction ratio at different angles for the proposed cyan polarizers exceeds 26. Analysis of the power density profiles for the transverse electric (TE) and transverse magnetic (TM) polarizations show that surface plasmon resonance and high refractive index contrast properties lead to excellent polarization features and high angular tolerance.