We present a powerful method to enhance the magnetic plasmon (MP) resonances of metamaterials composed of periodic arrays of U-shaped metallic split-ring resonators (SRRs) for high-quality sensing. We show that by suspending the metamaterials to reduce the effect of the substrate, the strong diffraction coupling of MP resonances can be achieved, which leads to a narrow-band mixed MP mode with a large magnetic field enhancement. It is also shown that for such a diffraction coupling, the magnetic field component of the lattice resonance mode of periodic arrays must be parallel to the induced magnetic moment in the metallic SRRs. Importantly, the sensitivity and the figure of merit (FOM) of the suspended metamaterials can reach as high as 1300 nm/RIU and 40, respectively. These results suggest that the proposed metamaterials may find great potential applications in label-free biomedical sensing.

We report a powerful method to enhance and modify the magnetic plasmon (MP) resonance in three-dimensional (3D) optical metamaterials consisting of periodic arrays of silver vertical split-ring resonators (VSRRs) for high-sensitivity sensing. By positioning the 3D metamaterials above a thick silver film separated by a silica dielectric spacer layer, the strong coupling between the MP resonance in the VSRRs and the surface plasmons polaritons (SPPs) propagating on the silver film can be realized and gives rise to an ultra-narrowband hybrid MP mode with a huge enhancement of magnetic fields. For the coupling to happen, the magnetic field direction of the SPPs should be parallel to the magnetic moment induced in the VSRRs. More importantly, because the ultra-narrowband hybrid MP mode is extremely sensitive to the surrounding media, the sensitivity and the figure of merit (FOM) of the 3D metamaterials can reach as high as 700 nm/RIU and 170, respectively, suggesting that the proposed 3D metamaterials hold potential applications in label-free biomedical sensing.

This paper presents a new theoretical proposal for a surface plasmon resonance (SPR) terahertz metamaterial absorber with five narrow absorption peaks. The overall structure comprises a sandwich stack consisting of a gold bottom layer, a silica medium, and a single-layer patterned graphene array on top. COMSOL simulation represents that the five absorption peaks under TE polarization are at f_I = 1.99 THz (95.82%), f_Ⅱ = 6.00 THz (98.47%), f_Ⅲ = 7.37 THz (98.72%), f_Ⅳ = 8.47 THz (99.87%), and f_V = 9.38 THz (97.20%), respectively, which is almost consistent with the absorption performance under TM polarization. In contrast to noble metal absorbers, its absorption rates and resonance frequencies can be dynamically regulated by controlling the Fermi level and relaxation time of graphene. In addition, the device can maintain high absorptivity at 0~50° in TE polarization and 0~40° in TM polarization. The maximum refractive index sensitivity can reach S_V = 1.75 THz/RIU, and the maximum figure of merit (FOM) can reach FOM_V = 12.774 RIU⁻¹. In conclusion, our design has the properties of dynamic tunability, polarization independence, wide-incident-angle absorption, and fine refractive index sensitivity. We believe that the device has potential applications in photodetectors, active optoelectronic devices, sensors, and other related fields.

We theoretically show a high-performance refractive index (RI) sensor that consists of a two-dimensional (2D) gold nanoparticle array lying on a dielectric slab waveguide. The sensor has high RI sensitivity and figure of merit (FOM), reaching 250 nm/RIU and 28, respectively. Such a high RI sensitivity and FOM result from a sharp fanolike resonance, which is caused by the interference between the localized surface plasmon resonances (LSPRs) excited on individual gold nanoparticles and the waveguide mode propagating in the adjacent dielectric slab. The interference condition is that the electric field of the waveguide mode must be parallel to the polarization direction of the LSPRs. Our work may have potential applications in ultra-compact biomedical sensing.

Here, we document a D-type double open-loop channel floor plasmon resonance (SPR) photonic crystal fiber (PCF) for temperature sensing. The grooves are designed on the polished surfaces of the pinnacle and backside of the PCF and covered with a gold (Au) film, and stomata are distributed around the PCF core in a progressive, periodic arrangement. Two air holes between the Au membrane and the PCF core are designed to shape a leakage window, which no longer solely averts the outward diffusion of Y-polarized (Y-POL) core mode energy, but also sets off its coupling with the Au movie from the leakage window. This SPR-PCF sensor uses the temperature-sensitive property of Polydimethylsiloxane (PDMS) to reap the motive of temperature sensing. Our lookup effects point out that these SPR-PCF sensors have a temperature sensitivity of up to 3757 pm/°C when the temperature varies from 5 °C to 45 °C. In addition, the maximum refractive index sensitivity (RIS) of the SPR-PCF sensor is as excessive as 4847 nm/RIU. These proposed SPR-PCF temperature sensors have an easy nanostructure and proper sensing performance, which now not solely improve the overall sensing performance of small-diameter fiber optic temperature sensors, but also have vast application prospects in geo-logical exploration, biological monitoring, and meteorological prediction due to their remarkable RIS and exclusive nanostructure.

Realizing tunable multi-band perfect absorption from ultraviolet to near-infrared range in nanophotonics and metamaterials is extremely significant for solar energy harvesting and optical sensors. Here, five narrowband and broadband perfect absorbers (PA) are simultaneously achieved in a simple 3D metamaterial consisting of aluminum (Al) standing U-shaped split-ring resonators (SUSRRs) on SiO ₂ /Al layer, which stems from the plasmonic hybridization between three high-order surface plasmon polarization (SPPs) and multiple localized surface plasmon (LSPs) localized both within the individual SUSRR as well as within the dielectric layer underneath the SUSRR. These penta-band perfect absorption peaks can be tuned by varying the temperature of the sealed ethanol with a temperature tuning performance of 0.331 nm/°C. Due to the two narrow perfect absorption at 473 nm and 157 nm being sensitive to the surroundings, our proposed Al SUSRR array as a high-sensitivity biosensor displays the ultra-large figure of merit ( FoM *) of 3.0×10 ⁴ and 1.55×10 ⁴ , which could be applied to gas sensing and the detection of the sub-nanometer thickness of analyte film.