Fig. 1. Optimization scheme for grating plano-concave lens. (a) Schematic diagram of structure and focusing of grating plano-concave lens in r-z plane; (b) schematic diagram of blazed structure construction; (c) diffraction of grating prism without blazed structure; (d) diffraction of grating prism with blazed structure

Fig. 2. Comparison of radial polarized light focal fields before and after modifying blazed structure. Focal field distributions of (a) hollow and (b) blazed lenses; focal field intensity contour line diagrams of (c) hollow and (d) blazed lenses; (e) normalized electric field intensity distribution along longitudinal direction based on peak intensity before optimization; (f) normalized electric field intensity distribution along lateral direction

Fig. 3. Relationship between focal field energy and height of blazed structure at different focal lengths. (a) f=4 μm; (b) f=6 μm; (c) f=8 μm; (d) relationship between enhancement factor Q and height of blazed structure

Fig. 4. Normalized electric field intensity distribution of focal field along longitudinal direction for constructing blazed structures in different regions. Number of blazed structure is (a) 10; (b) 20

Fig. 5. Manipulation of focal field by amplitude of incident light. (a) Relationship between Gaussian radially polarized light amplitude and w₀; (b) schematic diagram of grating lens area division; (c) normalized distribution of electric field intensity along longitudinal direction of focal field through hollow lens; (d) normalized distribution of electric field intensity along longitudinal direction of focal field through blazed lens