Fig. 1. Schematic of experimental setup (top view)

Fig. 2. Femtosecond laser intensity distribution after passing through polarizer LP2 and relationship between the position of dark stripe and rotation angle of polarizer. (a) Femtosecond laser intensity distribution after passing through polarizer LP2 recorded by CCD camera in dashed box of Fig. 1; (b) relationship between the position of dark stripe and rotation angle of LP2

Fig. 3. Intensity distributions and corresponding periodic structures fabricated on tungsten surface. (a)-(d) Intensity distributions of femtosecond vector beam recorded by CCD camera after passing through horizontal polarizer; (e)-(f) SEM pictures of periodic structures on tungsten surface fabricated by femtosecond laser with different polarization distributions

Fig. 4. Comparison between predicted and actual shapes of ripples

Fig. 5. Relationships among polarization variation period, bottom length of curved ripples and defocusing distance. (a) Polarization variation period versus bottom length of curved ripples when defocusing distance is 0.1 mm; (b) bottom length of curved ripples versus polarization variation period and defocusing distance

Fig. 6. Micro-Raman spectra of polished tungsten surface and curved ripple covered surface when excitation laser wavelength is 785 nm

Fig. 7. Micro-reflectance spectra of polished tungsten surface and curved ripple covered surface