Size parameter effect of dielectric small particle mediated nano-hole patterning on silicon wafer by femtosecond laser

By use of a polystyrene particle with a fundamental (800 nm) and a second-harmonic (400 nm) wave of a femtosecond Ti:sapphire laser, nano-hole patterning properties on a silicon wafer were experimentally compared by keeping the size parameter constant. With the 800-nm wave, the patterned hole diameter ranged from 100 to 250 nm and the depth ranged from 20 to 100 nm. With the 400-nm wave, the hole diameter ranged from 50 to 200 nm while the depth ranged from 10 to 60 nm. The patterned diameter and the depth of patterned nano-holes were also controllable by the laser fluence. By the 3D finite-difference time-domain method it is numerically predicted that if the size parameter is kept at π approximately, the nano-hole patterning is efficiently performed even in the ultraviolet region of the spectrum.