  Surfaces patterned with arrays of quasi-periodic air holes having conical
depth profile have been studied for their effectiveness in suppressing
air-substrate reflection in the wavelength range of 450-1350 nm (limited by our
measurement). The role of quasi-periodic air-hole pattern, depth of holes and
launch angle on the observed antireflection behavior are investigated. The
average optical transmittance of the patterned quartz substrate at near normal
incidence is more than 97% and reflectance is less than 2%. Patterned quartz
surfaces with 450 nm thin graded rarefaction region maintain the antireflective
property up to 30{\deg} (limited by our measurements) angle of incidence.
