Asymmetric diffraction from two-component optical gratings made of passive and lossy materials

Diffraction with asymmetric enhancement and suppression, and alternating contrast for symmetric diffraction orders is demonstrated from planar two-component optical gratings made of passive/lossy materials. Simulations agree well with the experimental diffraction pattern of the fabricated sample. Our fabrication approach uses simple, standard planar micro/nano lithography employing one photoresist and one dye. No 3D profiling is needed. The phenomena is due to the left-right asymmetric material distribution in the periodic grating, which gives rise to non-reciprocal light coupling for diffraction to the positive and negative orders.