Antireflection behavior of silicon subwavelength periodic structures for visible light

We describe subwavelength surfaces etched into silicon wafers that exhibit antireflection characteristics for visible light. The wafers are fabricated by holographically recording a crossed-grating in a photoresist mask followed by reactive-ion etching to transfer the primary mask onto the silicon substrate. The dependence of reflectivity on the wavelength and angle of incidence is measured. The overall antireflection performance of the corrugated silicon wafers is compared with that of standard thin-film stacks, and is interpreted with the effective medium theory and with simulation results obtained from rigorous computations.