Fig. 1. (a) Experimental setup of non-contact microsphere femtosecond laser irradiation. (b) Side view of microsphere focusing with femtosecond laser beam.

Fig. 2. (a) SEM and (b) AFM images, as well as (c) corresponding cross-sectional profile of sub-50 nm nano-lines created at the laser fluence of 0.38 mJ/cm² and scanning speed of 100 μm/s.

Fig. 3. Formation mechanism of microsphere femtosecond laser irradiation. (a) Focusing via 50 μm microsphere by 800 nm laser irradiation. (b) TPA of Sb₂S₃ thin films under 800 nm femtosecond laser irradiation. (c) top threshold and high-repetition-rate femtosecond laser induced incubation effects.

Fig. 4. Different nano-structures created by microsphere femtosecond laser irradiation on 30 nm thick Sb₂S₃ thin films. Nano-dots fabricated at different laser fluences of (a) 0.30, (b) 0.42, and (c) 0.46 mJ/cm². Single nano-lines made at a scanning speed of 100 μm/s and different laser fluences of (d) 0.38, (e) 0.42, and (f) 0.46 mJ/cm². Irradiation results of arbitrary structures. (g) Irregular sub-50 nm triple nano-lines, (h) single sub-100 nm, and (i) double sub-50 nm wavy nano-lines.

Fig. 5. SEM and AFM images of the nano-structures created on Sb₂S₃ thin films at the film thickness of (a–c) ~25, (d–f) ~35, and (g–i) ~42 nm. (j) Linear fitting analysis of the FWHM vs ablation depth.

Fig. 6. SEM images of the reflective grating by microsphere femtosecond laser irradiation at a period of (a) 1, (c) 2, and (e) 4 μm, respectively. The diffraction pattern, diffraction intensity, and angle observed in reflection for grating structures at a period of (b) 1, (d) 2, and (f) 4 μm, respectively. The number refers to the diffraction order of each reflective grating.