Design and fabrication of an all-dielectric grating with top-hat high diffraction efficiency over a broad spectral range

Between 98% and 100% flat top efficiency –1 st order TE diffraction over a 40 nm wavelength range centered at 800 nm can be obtained by an all-dielectric grating structure where the corrugation is etched in a high index layer unlike in the state of the art. 98% maximum efficiency and a wide-band top-hat diffraction efficiency spectrum are demonstrated experimentally.