Method for designing highly efficient composite transmission gratings

We present and validate a new method for designing transmission gratings with high efficiency for the 1st diffraction order across the visible spectrum. The high efficiency is achieved by redirecting light to the 1st order via asymmetric composite elements, which scatter light in the same direction as the 1st diffraction order. By focusing on increasing the directional scattering of the grating elements, the design remains simple yet effective. As a result, the gratings are relatively easy to fabricate. Measurements of fabricated gratings show a relative increase of over 40% for a large part of the visible spectrum.