  The high UV laser dose at 193 nm induces grooves on poly allyl diglycol
carbonate PADC (CR39) at normal irradiation. The spatial period exhibits to be
nearly invariant for azimuth and polar angles indicating a loose dependence on
the incident angles but the LIPSS (Laser-induced periodic surface structures)
are always parallel to the P polarization component of the incident beam. The
most common approach to explain LIPSS formation is related to the Sipe theory
which does not account for all the observed phenomena especially LIPSS with
periodicity larger than the laser wavelength. In fact the LIPSS is a multi
parameter mechanism based on surface rippling, acoustic modulation and laser
ablation and etc. In experiment with CR-39 polymer, laser irradiation produce a
very tiny melting layer of mixture of monomer due to depolymerization on the
surface and it seems capillary wave is responsible for grooves formation.
