Analysis of a Gradient Index Metamaterial Blazed Diffraction Grating

The equivalent of a blazed diffraction grating can be formed from an array of metamaterial elements arranged so as to produce a linear gradient in the effective refractive index. By spreading the gradient over a multiwavelength distance, and repeating the pattern many times, a gradient index (GRIN) diffraction grating is formed. Using lithographically patterned, metallic metamaterial elements, dozens of distinguishable phase levels can be implemented by slightly modifying the design of each successive metamaterial element. We analyze here a multilayer metamaterial diffraction grating designed for operation at 10.6 μm, exploring the impact of material losses and impedance mismatch on the diffraction efficiency.