Fig. 1. Experimental setup for femtosecond laser interference using two cylindrical lenses. HWP: half-wave plate, GP: Glan prism, BS: beam splitter. The double arrow and letter E represent the laser polarization.

Fig. 2. Schematic of the setup for optical measurements.

Fig. 3. (a) Schematic diagram of laser processing of fused silica surface. Green squares indicate the regions at which the images in (b) and (c) were measured. SEM images of LSFLs obtained using (b) cylindrical lens and (c) circular lens. The laser fluence is 2.8 J/cm², and the scanning velocity is 3.1 mm/s. The scale bar in (b) and (c) is 5 μm. (d) SEM image of cross section of LSFL on fused silica obtained using a laser focused by a cylindrical lens. (e) and (f) are the 2D-FT images of the LSFLs in (b) and (c), respectively. (g) is the FT spectra for k_y= 0 μm^–1.

Fig. 4. SEM images of micro-/nanostructures on fused silica produced by TBI, where each laser beam had a fluence of 2.8 J/cm², and the scanning velocity was (a) 8.2 and (b) 4.8 mm/s. (c) and (d) are SEM images of the red areas in (a) and (b), respectively. The green arrow represents the scanning direction. The scale bar is 20 μm in (a) and (b), and is 2 μm in (c) and (d).

Fig. 5. SEM images of micro-/nanostructures on fused silica obtained at a scanning velocity of 6.2 mm/s and laser fluences of (a) 1.8, (b) 2.1, (c) 2.8, and (d) 3.2 J/cm². The scale bar is 2 μm. Double arrow indicates the laser polarization direction.

Fig. 6. LIPSS period and duty cycle versus fluence at a constant scanning velocity of 6.2 mm/s.

Fig. 7. SEM images of micro-/nanostructures on fused silica obtained at a constant laser fluence of 2.8 J/cm² and a scanning velocity of (a) 12, (b) 6.2, (c) 4.8, and (d) 2.4 mm/s. The scale bar is 5 μm. The double-headed arrow and E in (a) indicate the incident laser polarization direction.

Fig. 8. LIPSS period and the duty cycle versus scanning velocity at a constant laser fluence of 2.8 J/cm².

Fig. 9. Optical characterization of structured silica surface with grating-like LIPSSs and spaced LIPSSs. (a) Diffraction spectra and (b) color images of structured silica with grating-like LIPSSs. (c) Diffraction spectra and (d) color images of structured silica with spaced LIPSSs.

Fig. 10. Optical image of falling petal pattern consisting of grating-like LIPSSs.

Fig. 11. Colorful optical images of two flower patterns consisting of grating-like LIPSSs oriented in different directions.(a) Schematic of the processing method. The green arrow represents the scanning direction. (b) Schematic of the flower pattern. (c) The images of flowers with grating-like LIPSSs in radial direction, and (d) in azimuthal direction. Insets show SEM images of the grating-like LIPSSs in the open red squares.