DYNAMICS OF LASER-INDUCED PERIODIC SURFACE-STRUCTURES IN EXCIMER-LASER ABLATION OF POLYMERS

In situ microscopy and optical diffraction studies of ripple structures produced on excimer laser ablated polymers are reported, allowing their development rate to be estimated and motion to be observed. The formation of these ''anomalous'' ripple structures (grating vector perpendicular to the polarized laser electric field direction) is analyzed within the framework of a model describing interference between the transmitted and diffracted beams at the surface. Experimental observations are consistent with theory if substantial modification of the (effective) optical constants of the polymer occurs under ablation conditions. A model describing the ripple dynamics under multipulse irradiation is reported and compared with the experimental findings.