Behavior of SPPs in chiral-graphene-chiral structure

Chiral Mechanical Effect of the Tightly Focused Chiral Vector Vortex Fields Interacting with Particles

The coupling of the spin-orbit angular momentum of photons in a focused spatial region can enhance the localized optical field's chirality. In this paper, a scheme for producing a superchiral optical field in a 4π microscopic system is presented by tightly focusing two counter-propagating spiral wavefronts. We calculate the optical forces and torques exerted on a chiral dipole by the chiral light field and reveal the chiral forces by combining the light field and dipoles. Results indicate that, in addition to the general optical force, particles' motion would be affected by a chiral force that is directly related to the particle chirality. This chiral mechanical effect experienced by the electromagnetic dipoles excited on a chiral particle could be characterized by the behaviors of chirality density and flux, which are, respectively, associated with the reactive and dissipative components of the chiral forces. This work facilitates the advancement of optical separation and manipulation techniques for chiral particles.

Examining the optical model of graphene via the photonic spin Hall effect

In modern optics, there are two general models to describe the behavior of light in graphene: the zero-thickness model and the slab model. The difference in physical phenomena predicted by the two models is very small, which is hardly distinguished by traditional measurement methods. Therefore, which model can describe the light-matter interaction in graphene more exactly is still a challenging issue. In this work, based on the sensitive optical phenomenon called the photonic spin Hall effect, the small difference can be magnified to a detectable level by the weak-value amplification. The experimental results show that the zero-thickness model can more accurately describe the interaction between light and monolayer or bilayer graphene, while the case of more than two layers, which can no longer be regarded as two-dimensional thickness, should be described by the slab model. Our results may provide information on light interacting with graphene for future investigation in photonics and optoelectronics.

Refractive Index Sensing Based on Multiple Fano Resonances in a Split-Ring Cavity-Coupled MIM Waveguide

A metal–insulator–metal (MIM) waveguide consisting of a circular split-ring resonance cavity (CSRRC) and a double symmetric rectangular stub waveguide (DSRSW) is designed, which can excite quadruple Fano resonances. The finite element method (FEM) is used to investigate influences of geometric parameters on the transmission characteristics of the structure. The results show that Fano resonances are excited by the interference between the DSRSW and the CSRRC. Among them, the resonance wavelengths of the Fano resonances are tuned by the narrow-band discrete state excited by the CSRRC, and the resonance line transmittance and profiles are tuned by the wide-band continuous state excited by the DSRSW. The sensitivity (S) can be up to 1328.8 nm/RIU, and the figure of merit (FOM) can be up to 4.80 × 104. Based on these advantages, the structure has potential applications in sensing in the sub-wavelength range.