Fig. 1. Structure of amplitude-tpye SOL and phase-tpye SOL

Fig. 2. Schematic diagram of diffraction focusing by SOL

Fig. 3. Distribution of axial intensity, transverse FWHM and focal spot intensity for SOL_1-4. (a)--(d) Axial intensity, transverse FWHM; (e)--(h) focal spot intensity

Fig. 4. Brief manufacturing process of amplitude-type SOL and phase-type SOL

Fig. 5. Diagram of ring belt manufacturing errors: (a) Transverse error; (b) longitudinal error

Fig. 6. Focusing performance of SOL₁. (a) Focal distance deviation; (b) transverse sidelobe ratio; (c) axial sidelobe ratio; (d) transverse focal size

Fig. 7. Focusing performance of SOL₂. (a) Focal distance deviation; (b) transverse sidelobe ratio; (c) axial sidelobe ratio; (d) transverse focal size

Fig. 8. Calculation result of focusing field with different phase modulation. (a) Axial light field distribution; (b) transverse light field distribution of focal plane

Fig. 9. SOL_2-4 focusing performance varying with phase modulation φ. (a) Spot center intensity; (b) transverse spot size

Fig. 10. Phase modulation and focused central intensity varying with the etching depth of SOL₅