Fig. 1. SEM images of subwavelength ripples induced by femtosecond laser pulses under repetition rates of (a) 10 kHz, (b) 50 kHz, (c) 100 kHz, (d) 200 kHz, and (e) 400 kHz at a pulse overlapping rate of 91%; (f) period of ripples and width of the scanning line as a function of repetition rate (SEM magnification, 2000; scale bar, 10 µm; white arrow, laser polarization).

Fig. 2. (a) Surface temperature decay of silicon after a single pulse irradiation; calculated temperature as a function of time for repetition rates of (b) 10 kHz and (c) 400 kHz, respectively.

Fig. 3. SEM images of ripple structures induced by femtosecond laser pulses under pulse overlapping rates of (a) 65%, (b) 83%, (c) 91%, (d) 96%, and (e) 98% at a repetition rate of 400 kHz; (f) period of ripples as a function of the pulse overlapping rate at repetition rates of 10 and 400 kHz (SEM magnification, 3500; scale bar, 5 µm; white arrow, laser polarization).

Fig. 4. (a) SP wavelength as a function of electron density; (b) effective dielectric constant (ε_eff) of air–nanostructure composite on LIPSSs and SP wavelength as functions of volume fraction of the silicon inclusion.

Fig. 5. Comparison of the surface morphology under (a)–(c) 10 kHz and (d)–(f) 400 kHz at pulse overlapping rates of (a), (d) 98%, (b), (e) 91%, and (c), (f) 83%, respectively (SEM magnification, 3500; scale bar, 5 µm; white arrow, laser polarization).