Surface plasmonic sensors have been widely used in biology, chemistry, and environment monitoring. These sensors exhibit extraordinary sensitivity based on surface plasmon resonance (SPR) or localized surface plasmon resonance (LSPR) effects, and they have found commercial applications. In this review, we present recent progress in the field of surface plasmonic sensors, mainly in the configurations of planar metastructures and optical-fiber waveguides. In the metastructure platform, the optical sensors based on LSPR, hyperbolic dispersion, Fano resonance, and two-dimensional (2D) materials integration are introduced. The optical-fiber sensors integrated with LSPR/SPR structures and 2D materials are summarized. We also introduce the recent advances in quantum plasmonic sensing beyond the classical shot noise limit. The challenges and opportunities in this field are discussed.

Plasmonic metasurfaces have been widely used in biosensing to improve the interaction between light and biomolecules through the effects of near-field confinement. When paired with biofunctionalization, plasmonic metasurface sensing is considered as a viable strategy for improving biomarker detection technologies. In this review, we enumerate the fundamental mechanism of plasmonic metasurfaces sensing and present their detection in human tumors and COVID-19. The advantages of rapid sampling, streamlined processes, high sensitivity, and easy accessibility are highlighted compared with traditional detection techniques. This review is looking forward to assisting scientists in advancing research and developing a new generation of multifunctional biosensors.

Beam steering in photonic crystals is significant in manipulating light beams. In this paper, we design self-collimation, beam splitting, and negative refraction effects in photonic crystals based on metallic pairs immersed in dielectric background. By using a single array of metallic pairs, a broadband and wide-angle self-collimation effect is achieved. Meanwhile, due to the extreme anisotropy, a beam splitting effect is achieved by utilizing the kissing of equi-frequency contours. We then restructure the unit cell with glide symmetry to achieve negative refraction effect in a wide frequency range and realize the effect of flat lens. To illustrate this phenomenon, a flat lens based on the restructured unit cell is designed and numerically demonstrated.