First-principles calculations were performed to investigate the electronic and magnetic properties of Ti 3 C 2 monolayer and its derivatives. We found that pristine Ti 3 C 2 monolayer acts as a magnetic metal, and magnetic moments come from Ti 2+ ions at two sides. Through doping nitrogen atoms, the spin moments is significantly reduced. On other hand, when two surfaces of Ti 3 C 2 monolayer are saturated by external groups, the magnetism will be spontaneously annihilated. Even for the saturation of one side, we also found that the magnetism of Ti 3 C 2 Y (Y is O and OH) monolayer is removed because of the invalidation of stoner instability. More importantly, we explored that both doping and surface modification will reduce the Curie temperature of Ti 3 C 2 monolayer. Therefore, our results shed a light on the way to get high-temperature magnetism in Ti 3 C 2 monolayer.

Optical angular momenta (AM) have attracted tremendous research interest in recent years. In this paper we theoretically investigate the electromagnetic field and angular momentum properties of tightly focused arbitrary cylindrical vortex vector (CVV) input beams. An absorptive particle is placed in focused CVV fields to analyze the optical torques. The spin-orbit motions of the particle can be predicted and controlled when the influences of different parameters, such as the topological charge, the polarization and the initial phases, are taken into account. These findings will be helpful in optical beam shaping, optical spin-orbit interaction and practical optical manipulation.

Rigorous vectorial focusing theory is used to study the imaging of small adjacent particles with a confocal laser scanning system. We consider radially polarized illumination with an optimized amplitude distribution and an annular lens to obtain a narrower distribution of the longitudinal component of the field in focus. A polarization convertor at the detector side is added to transform radial polarization to linear polarization in order to make the signal detectable with a single mode fiber.

Light scattering by a grating of the metal (Ag)-coated nanocylinders supported on the dielectric substrate is investigated using an accurate and rigorous formulation based on the recursive algorithm combined with the lattice sums technique. The proposed approach could be applied easily to the various configurations of the grating composed of the metal or metal-coated nanocylinders with different types and locations of the excitation sources. Special attention is paid to the three types of resonances: (a) surface plasmon resonances associated with the metal nanocylinders, (b) Rayleigh anomalies related with the periodic nature of the grating, and (c) resonances due to the coupling between the grating and the dielectric substrate. Near-field distribution of the magnetic field, which is parallel to the axis of the nanocylinders, is investigated numerically. Physical insight is given to the localization of the field along the interfaces of the metal nanocylinders, formation of the strong reflected field by the grating, and the field enhancement at the surface of the dielectric substrate. The accuracy of the numerical analyses has been tested based on the principle of the energy conservation. All these features are technologically important and have wide practical application from the viewpoint of the flexible design and fabrication of the plasmonic optical devices.

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