Fabrication of complex periodic micro/nanopatterns by multiple interfered femtosecond laser pulses on thin solid films

Complex periodic micro/nanopatterns have been fabricated on zinc acetate thin films by the irradiation of three or two interfered 800 nm femtosecond laser beams. Three interfered laser beams produce 2D periodic microflower structures with petal sizes as small as 100 nm, which is much smaller than the laser wavelength and its diffraction-limited scale. While two interfered femtosecond laser beams lead to 2D arrayed grating-like patterns with a long period of ∼3.0 μm and a short period of ∼150 nm in two orthogonal directions, respectively. Theoretical calculation indicated that the long periodicities of flower/grating-like patterns were attributed to the interferential intensity distribution, whereas petal structures of microflowers or short periodicities of grating-like patterns were determined by the interferential polarisation distribution.