This paper presents a graphene-Au coated photonic crystal fiber (PCF) sensor in the visible regime. Designing a side-polish D-shaped plane over the PCF’s defect of the periodic air holes can effectively enhance the evanescent field. Graphene on gold can enhance the sensor’s sensitivity because it can stably adsorb biomolecules and increase the propagation constant of the surface plasmon polariton (SPP). Using the finite element method (FEM), we demonstrated that the sensing performance is greatly improved by optimizing the PCF’s geometric structural parameter. The proposed PCF sensor exhibited high performance with a maximum wavelength sensitivity of 4200 nm/RIU, maximum amplitude sensitivity of 450 RIU⁻¹, and refractive index resolution of 2.3 × 10⁻⁵ RIU in the sensing range 1.32–1.41. This research provides a potential application for the design a new generation of highly sensitive biosensors.

By coating graphene oxide (GO) onto the surface no-core fiber (NCF), we designed a single-mode no-core single-mode (SNS) fiber Step-Index Distribution sucrose sensor. With wavelength demodulation and the beam propagation method (BPM), the sensor without a GO coating was studied in the low RI range of 1.33~1.389, and the high RI range of 1.389~1.4185. The experiments show that the RI sensitivity of the sensor respectively reaches 132.9 nm/RIU and 292.22 nm/RIU. Both the numerical simulation and the experiments are highly consistent with the theoretical analysis results. Especially, having coated GO on the NCF for sensitization, a high sensitivity was achieved for the response to sucrose concentration solutions. The sensor’s RI sensitivity was increased from 132.9 nm/RIU up to 1348.67 nm/RIU in the ultra-narrow range of 1.33 to 1.3385. This result provides a theoretical and experimental basis for the enrichment and development of sensor detection with a low threshold sucrose concentration.

We propose a scheme using cooperative interaction of antiphase resonance modes to enhance optical trapping in plasmonic nanostructures. This is implemented with a subwavelength array of asymmetric binary nanogrooves (e.g. different depths) in metal. When damping and inter-coupling of antiphase fields in the nanogrooves are mediated satisfying a critical condition, light can be cooperatively trapped in the nanogrooves, demonstrating perfect absorption at nearly the intrinsic resonance frequency of the deeper nanogrooves. A harmonic oscillator model is developed to interpret the cooperative interaction processes. The phenomenon has been also implemented in asymmetric ternary nanogroove arrays. In terms of compositions and intra-coupling mechanisms, the asymmetric binary/ternary plasmonic nanostructure arrays are crystalline molecular-metamaterials, analogous to electronic crystals composed of covalence-bond molecules.

Transversely localized resonance of antisymmetric-bound surface plasmons (ab-SP) at ultrathin metal stripes in a subwavelength array suppresses optical transmission in a broadband. Here, asymmetric binary arrays of ultrathin metal stripes are proposed to introduce a narrow transmission peak in the stop-band (i.e., plasmon-induced transparency), based on destructive interference of antisymmetrically excited ab-SP resonance modes at the neighboring binary metal stripes. The phenomenon is numerically demonstrated and explained with a mesoscopic model, in which mesoscopic interaction processes are abstracted as different transmission channels to cooperatively result in the narrow peak in a broad transmission valley. In spite of the ultrathin feature of the structure for convenience in fabrication, its excellent performance facilitates potential applications.