Fig. 1. Mechanism of laser interference ablation on Si. (a) Two-beam interference ablation; (b) HF etching process; (c) final sample

Fig. 2. Analysis on nanosecond laser interference on Si. (a) Schematic of nanosecond laser interference; (b) maximumlight intensity as a function of period change; (c) surface light intensity distribution of two-beam interference

Fig. 3. Effect of exposure time of laser interference on morphology of periodic micro/nanostructure. (a) Atomic force microscopy (AFM) images at exposure time of 0.5 s; (b) AFM images at exposure time of 1s; (c) AFM images at exposure time of 10 s; (d) AFM images at exposure time of 20 s

Fig. 4. Effect of period on structural evolution. (a)-(c) AFM images at exposure time of 1 s, 5 s, and 10 s when period is 1.1 μm; (d) SEM image of Fig. 4(c); (e)-(f) SEM images at exposure time of 1 s and 5 s when period is 0.6 μm; (g) SEM image when period is 300 nm; (h) SEM image of structure ablated by only one beam

Fig. 5. Variation in structural depth with exposure time and power. (a) Depth as a function of exposure time; (b) depth as a function of power

Fig. 6. FDTD simulation for light intensities propagating in different media. (a) Free space; (b) silicon surface; (c) structured Si surface