Fig. 1. Schematic of experiment setup for manufacturing sub-wavelength periodic surface structures using double time-delayed femtosecond lasers

Fig. 2. Characterization of 2D arrays of nanosquares， nanocircles （nanoellipses） and 1D nanostrips structures induced by double femtosecond lasers

Fig. 3. Characterization of 2D arrays of nanosquares and nanotriangles structures， as well as morphology transition between them

Fig. 4. Morphology transition from 2D array of nanotriangles to 1D nanogratings structure induced by double femtosecond lasers

Fig. 5. Large area of uniform 2D arrays of nanocircles and nanotriangles structures induced by double femtosecond lasers

Fig. 6. Proposed physical models for formation of 2D periodic array structures induced by double femtosecond lasers