Fig. 1. Schematic diagram of diffraction focusing of SOL.

Fig. 2. Focused light field of SOL₁ by FDTD simulation: (a) On-axis intensity distribution; (b) transverse intensity distribution in the focal plane (Y-direction).

Fig. 3. Focusing performance of SOL (FDTD): (a) Transverse size; (b) central intensity.

Fig. 4. Focused light field of SOL₂ by FDTD simulation: (a) On-axis intensity distribution; (b) transverse intensity distribution in the focal plane (Y-direction).

Fig. 5. Electric field distribution of SOL₁ by FDTD simulation: (a) Uniform plane beam illumination; (b) w₀ = a/2 Gaussian beam illumination.

Fig. 6. Focused light intensity of SOL by VAS calculation under BG radially polarized illumination: (a), (b) SOL₁; (c), (d) SOL₂.

Fig. 7. Schematic diagram of diffraction focused imaging by SOL under oblique illumination.

Fig. 8. Schematic diagram of diffraction focusing by SOL under oblique illumination.

Fig. 9. Focusing results of amplitude-type SOL under oblique illumination: (a), (c), (e) SOL₅; (b), (d), (f) SOL₆.

Fig. 10. Focal spot size of SOL under oblique illumination: (a) FWHM_x ; (b) FWHM_z .

Fig. 11. Focal intensity of SOL varying with oblique illumination angle.

Fig. 12. Angle position of focusing spot: (a) - ; (b) - .

Fig. 13. Field curvature of SOL: (a) SOL₃; (b) SOL₄.