Fig. 1. Natural compound eye of insects. (a) SEM images of compound eye of mosquito^[16]; (b) SEM images of compound eye of drosophila^[17]; (c) optical micrograph of the structure of bee ommatidia^[18]

Fig. 2. Single-step ultrafast laser ablation for fabrication of microlens array^[20]. (a) Schematic of the fabrication process of microlens array by ultrafast laser ablation of PDMS, where the insert is the mechanism of microlens generation by single femtosecond laser pulse ablation; (b) SEM image of fabricated microlens array by single femtosecond laser pulse

Fig. 3. Fabrication of microlens array by etching-assisted ultrafast laser ablation. (a) Fabrication process schematic of microlens array by wet-etching-assisted femtosecond laser^[21]; (b) SEM image of fabricated microlens array by wet-etching-assisted femtosecond laser^[21]; (c) fabrication process of microlens array by dry-etching-assisted femtosecond laser^[31]; (d) SEM image of fabricated microlens array by dry-etching-assisted femtosecond laser^[31]

Fig. 4. Fabrication of nonuniform or heterogeneous microlens array by ultrafast laser direct writing. (a) SEM image of focal varying microlens array^[38]; (b) SEM image of dual-focus microlens array^[39]; (c) schematic illumination of fabrication process of parabolic cylindrical microlens array with a Bessel beam^[40]; (d) LSCM image of cylindrical microlenses fabricated with a Bessel beam^[40]; (e) schematic of fabrication process of microlens by preprogrammed laser direct writing^[41]; (f) SEM images of microlenses with various curved surfaces prepared by preprogrammed laser direct writing^[41]

Fig. 5. Microlens arrays fabricated by single pulse ultrafast laser-induced swelling. (a) Schematic illustration of PMMA microlens array fabrication by laser-induced swelling^[42]; (b)(c) SEM images of fabricated microlens array by single pulse ultrafast laser-induced swelling^[42-43]; (d) SEM image of microswelling structure after laser irradiation at different depths^[44]

Fig. 6. Large size microlens array fabrication by femtosecond laser-induced swelling. (a) Schematic of fabrication process of microlens array by femtosecond laser-induced swelling of two-layer polymers^[45]; (b) SEM and LSCM images of microlens array fabricated by femtosecond laser-induced swelling of two-layer polymers^[45]; (c) SEM images of cross section of microlens array obtained at different pulse numbers^[46]; (d) diagram for fabrication of microlens array by multifocal laser processing^[47]

Fig. 7. Fabrication of superhydrophobic compound eye by single-step femtosecond laser ablation^[48]. (a) Schematic illustration of fabrication process of self-cleaning artificial compound eye with different periods; (b) SEM images of microlens array with different periods fabricated by femtosecond laser ablation, and the insets are water contact angle on different surfaces

Fig. 8. Fabrication of superhydrophobic compound eye with fully covered micro/nano structures by ultrafast laser^[49]. (a) Schematic illustration of fabrication process of self-cleaning artificial compound eye with fully covered micronano structures by ultrafast laser; (b) SEM image of self-cleaning artificial compound eye with fully covered micronano structures; (c) LSCM image of self-cleaning artificial compound eye with fully covered micronano structures

Fig. 9. Fabrication of superhydrophobic compound eye with micro/nano structures at the gaps of microlens by ultrafast laser. (a) Schematic illustration of fabrication of self-cleaning artificial compound eye with criss-cross reticular rough structures around the convex microlenses by ultrafast laser^[50]; (b) SEM image of artificial compound eye with criss-cross reticular rough micro/nano structures around the microlens array^[50]; (c) schematic illustration of fabrication of self-cleaning artificial compound eye with criss-cross reticular rough structures around the concave microlenses by ultrafast laser^[51]

Fig. 10. Fabrication of self-cleaning artificial compound eyes by laser combined with other technologies. (a) Schematic illustration of fabrication of self-cleaning artificial compound eye with fully covered nanopillars by nanoimprinting and laser-induced swelling^[52]; (b) SEM images of self-cleaning artificial compound eye with fully covered nanopillars^[53]; (c) SEM images of self-cleaning artificial compound eye fabricated by chemical growth and laser-induced swelling^[54]

Fig. 11. Ultrafast laser direct writing of wide-field-of-view artificial compound eye. (a) Fabrication of wide-field-of-view artificial compound eye by equal-height and equal-arc ultrafast laser scanning^[55]; (b) SEM images of single microlens and gapless hexagonal wide-field-of-view artificial compound eye fabricated by equal-height and equal-arc ultrafast laser scanning^[55]; (c) SEM images and three-dimensional laser confocal microscopy image of wide-field-of-view BSA-based artificial compound eye^[57]

Fig. 12. Wide-field-of-view artificial compound eye by ultrafast laser processing of curved substrate. (a) Schematic illustration of fabrication process of wide-field-of-view artificial compound eye by first point-by-point laser exposure on the curved lens and subsequent HF-assisted etching^[58]; (b) SEM images of closely-packed wide-field-of-view artificial compound eye^[58]; (c) schematic of aided fabrication of a wide-field-of-view artificial compound eye by spatial light modulation^[60]; (d) morphologies of artificial compound eye fabricated by spatial light modulation^[60]

Fig. 13. Fabrication of wide-field-of-view artificial compound eye by first ultrafast laser irradiation and subsequent hot embossing. (a) Schematic illustration of fabrication of wide-field-of-view artificial compound eye^[62]; (b) SEM images of wide-field-of-view artificial compound eye^[62]

Fig. 14. Fabrication of multifunctional artificial compound eye by combining ultrafast laser and other nanotechnologies. (a) Schematic illustration of fabrication process of multiscale artificial compound eye by etching-assisted ultrafast laser ablation and microfluidic technology^[65]; (b) SEM images of multiscale artificial compound eye fabricated by nanoimprinting, laser-induced swelling, and air-assisted deformation^[53]; (c) SEM images of multiscale artificial compound eye fabricated by ultrafast laser irradiation, air-assisted deformation, and chemical growth^[54]