Fig. 1. Femtosecond laser direct writing system

Fig. 2. SEM images of different laser energy densities and pulse numbers

Fig. 3. Simulation results. (a) Schematic of initially formed LSFL structure; (b) electric field distribution on the material surface

Fig. 4. Evolution of laser direct writing induce LSFL on the surface of As₂S₃ with different overlap ratios and different energy densities

Fig. 5. Schematic diagram of the formation process of LSFL. (a) Formation region of two adjacent laser pulses directly writing LSFL; (b) LSFL structure formed by multiple laser pulses

Fig. 6. LSFL processed by femtosecond laser through large-area scanning under the focus of 2.5× objective lens.(a)-(c) Color effect of LSFL at different angles; (d) SEM image of large-area LSFL structure; (e) transmission spectra of large-area LSFL structures; (f) partial enlarged view of the 5-12 μm band

Fig. 7. Multi-angle diffraction experiment. (a) Schematic diagram of the color test system; (b)-(f) when the illumination angle is 34°, 40°, 53°, 62°, and 69°, the corresponding spectra under different rotation angles

Fig. 8. Preparation of snowflake-like structures on As₂S₃ glass materials. (a) Diffraction phenomenon occurs when natural light irradiates the periodic structures; (b)-(d) material surface exhibits different color effects at different angles