Fig. 1. COMSOL simulation results. (a) Diameter of microsphere is 5 µm; (b) diameter of microsphere is 1 µm

Fig. 2. Effects of microsphere diameter and laser wavelength on machining accuracy

Fig. 3. Schematic diagram of experimental process

Fig. 4. Silica microsphere monolayer dense array

Fig. 5. Schematic diagram of laser light path

Fig. 6. Effect of laser wavelength on gold film structure (25 nm gold film, 4.82 µm microspheres and 10 mJ/cm² energy density). (a) 532 nm; (b) 355 nm; (c) 266 nm; (d) variation of hole diameter on gold film with energy density at different wavelengths

Fig. 7. Effect of microsphere diameter on gold film structure (532 nm laser, 25 nm gold film and 30 mJ/cm² energy density). (a) 4.82 µm; (b) 2.53 µm; (c) 1.49 µm; (d) variation of hole diameter on gold film with energy density under different microsphere diameters

Fig. 8. Effect of gold film thickness on gold film structure (532 nm laser, 4.82 µm microspheres and 20 mJ/cm² energy density). (a) 10 nm; (b) 25 nm; (c) 40 nm; (d) variation of hole diameter on gold film with energy density under different gold film thicknesses

Fig. 9. Processed holes with diameter about 100 nm at optimal parameter (laser wavelength is 532 nm, gold film thickness is 25 nm, microsphere diameter is 1.49 μm and laser energy density is 25 mJ/cm²)

Fig. 10. Effect of step on line processing. (a) Only one point is machined; (b) machining step is 400 nm; (c) machining step is 800 nm; (d) machining step is 1200 nm

Fig. 11. Effect of energy density on line processing. (a) Energy density is 25 mJ/cm²; (b) energy density is 23 mJ/cm²; (c) energy density is 20 mJ/cm²

Fig. 12.

Processed patterns. (a) Processed pattern T on 4.82 µm microsphere; (b) processed pattern C on 4.82 µm microsphere; (c) processed pattern O on 2.53 µm microsphere