  We report a novel, polarization dependent, femtosecond laser-induced
modification of surface nanostructures of indium, gallium, and arsenic grown on
silicon via molecular beam epitaxy, yielding shape control from linear and
circular polarization of laser excitation. Linear polarization causes an
elongation effect, beyond the dimensions of the unexposed nanostructures,
ranging from 88 nm to over 1 um, and circular polarization causes the
nanostructures to flatten out or form loops of material, to diameters of
approximately 195 nm. During excitation, it is also observed that the generated
second and third harmonic signals from the substrate and surface nanostructures
increase with exposure time.
