into a substantially planar surface or on a substantially non planar surface a convex or concave lens or a convex or concave mirror are an examples of the non planar surfaces based upon analysis using rigorous coupled wave rcw theory it has been determined that the reflectance of a subwavelength structure is a function of the spatial period the feature size refractive index of the material and the depth of the structure these features can be packed as squares and hexagonal close packing can further improve the anti reflection performance lithography techniques e g gray scale masking techniques and holographic techniques allow the patterning of smooth profiles fig2 is a schematic view of a subwavelength surface structure that has a smooth contour the structure has a bulk component 101 and a ridged or roughened surface component 102 the surface component 102 has a sinusoidal or alternatively triangular cross section having an amplitude 103 and a distance between peaks 104 which is the pitch the mean peak width 105 is the feature size the illuminating wave 106 can be at normal or any angle of incidence 107 due to the geometric anisotropy of the grating structure the two orthogonally polarized optical.