  We present experimental evidence of a fourth order process in electric field
in supercontinuum generation. We also show laser induced polarization
preference in the supercontinuum generating media. These results have become
possible through the choice of isotropic and anisotropic samples interacting
with ultrashort laser pulses of changing ellipticity. Laser polarization
emerges as an important control parameter for the highly nonlinear phenomenon
of supercontinuum generation.
