Fig. 1. Electric field intensity, polarization, and phase distributions of tightly focused cylindrical vector beams (n=1,NA=0.9,β₀=1). (a)-(d) Radially polarized vector beam; (e)-(h) azimuthally polarized vector beam. (a), (e) Distribution of total electric field intensity (|E|²=|E_x|²+|E_y|²+|E_z|²) in xy plane; (b), (f) distribution of total electric field intensity in xz plane; (c), (g) transverse electric field intensity (|E_⊥|²=|E_x|²+|E_y|²); (d), (h) longitudinal electric field intensity (|E_z|²). The dark arrows represent polarization states and insets are for phase distributions

Fig. 2. Excitation and manipulation of plasmonic dipole modes with vector beam. (a) Longitudinal electrical dipole in an Au nanosphere excited by tightly focused radially polarized vector beam^[33]; (b) electric vector distribution of radial vector focal field (upper panel) and electric dipole distance in any direction excited by it (below panel) ^[35]; (c) magnetic dipole mode excited by azimuthally polarized vector beam^[36]

Fig. 3. Excitation of plasmonic dark modes with vector beam. (a) Electric quadrupole mode of Au nanorod generated by a tightly focused radially polarized vector beam^[44]. Left and right panels are for excitation configuration relative to nanorod and scattering spectra of nanorod at different y displacements, respectively; (b) selectively exciting azimuthal and radial plasmonic dark modes by vector beam in Au nanodisk heptamers ^[45]; (c) toroidal dipole mode excited in gold film-dielectric layer-hexamer using radially polarized vector beam^[46]. Left and right panels are schematics of plasmonic structure as well as magnetic field distributions of vector beam and scattering spectrum of toroidal dipole mode, respectively

Fig. 4. Efficient excitation and applications of plasmonic modes. (a) Manipulation of interaction between plasmonic dipole mode and fluorescence molecule using tightly focused radially polarized vector beam^[47]; (b) excitation of azimuthal plasmonic dark mode and its applications in surface enhanced Raman spectroscopy^[48]; (c) radial breathing mode in silver nanoaperture and its optical trapping of 5 nm dieletric nanosphere^[49]; (d) optical trapping of 2 nm quantum dot^[50] using plasmonic cavity mode excited by radial plasmonic breathing mode; (e) tuning frequency of second harmonic generation from octamer nanodisk using mode matching technique based on vector beam^[51]

Fig. 5. Schematic illustration of plasmon hybridization in metallic nanoshell^[52]

Fig. 6. Coupled harmonic oscillator model describing plasmonic mode coupling

Fig. 7. Controlling plasmonic mode coupling with vector beam. (a) Out-of-phase bonding and antibonding dark mode of Au nanosphere dimer excited by azimuthal and radial vector beams^[55]; (b) deterministically tuning local field distribution in plasmonic nanocluster using Hermite-Gaussian beams^[56], in which left to right panels correspond to target local field, vector beam excited local field as well as amplitudes and phases of Hermit-Gaussian beams for constructing vector excitation; (c) Fano resonance of Au nanosphere dimer under excitation of vector beam^[57]; (d) double Fano resonances in a split ring oligomer structure excited by azimuthally polarized vector beam^[58]

Fig. 8. Applications of vector beam controlled plasmonic mode coupling^[62]. (a) Reversible optical binding force in a plasmonic heterodimer by controling mode coupling under illumination of radially polarized vector beam; (b) enhanced second harmonic generation in a plasmonic trimer based on control of plasmonic mode coupling; (c) applications of structural defect (left panel) and beam misalignment (right panel) using plasmonic Fano resonance excited by azimuthally polarized vctor beam

Fig. 9. Manipulating scattering pattern of plasmonic core-shell nanosphere with tightly focused azimuthally polarized vector beam^[70]. (a) Distributions of electromagnetic components of azimuthally polarized vector beam along x direction of focal plane; (b) in-plane electric field (|E_⊥|²=|E_x|²+|E_y|²) and magnetic field intensity (|ZH_⊥|²=|ZH_x|²+|ZH_y|²) of azimuthally polarized vector beam; (c) spectrum distribution of phase difference between Mie coefficients a₁ and b₁ of core-shell nanospheres; (d) far-field unidirectional scattering distribution of core-shell nanosphrere at λ=1550 nm

Fig. 10. Unidirectional scattering of Au nanosctructure using vector beam control. (a) Schematic of far-field scattering of Au nanosphere controlled by tightly focused vector beam^[12]; (b) change in focal field position of Au nanospheres can cause in-plane radiation field to shift from isotropic (center image) to unidirectional scattering (left and right images) ^[12]; (c) application of unidirectional scattering of Au nanospheres in waveguide directional coupling ^[12]; (d) optical path diagram of tightly focused Hermite-Gaussian beam exciting slotted antenna surface plasmon polariton^[71]; (e) excitation of magnetic dipole modes in slot antennas (upper panel) and surface plasmon polaritons with unidirectional transmission (lower panel) ^[71]; (f) application of asymmetric transmission of surface plasmon polaritons in nanometric displacement sensing^[71]