title: Design and fabrication of a metamaterial gradient index diffraction grating at infrared wavelengths.
abstract: We demonstrate the design, fabrication and characterization of an artificially structured, gradient index metamaterial with a linear index variation of Δn ~ 3.0. The linear gradient profile is repeated periodically to form the equivalent of a blazed grating, with the gradient occurring across a spatial distance of 61 μm. The grating, which operates at a wavelength of 10.6 μm, is composed of non-resonant, progressively modified "I-beam" metamaterial elements and approximates a linear phase shift gradient using 61 distinguishable phase levels. The grating structure consists of four layers of lithographically patterned metallic I-beam elements separated by dielectric layers of SiO(2). The index gradient is confirmed by comparing the measured magnitudes of the -1, 0 and +1 diffracted orders to those obtained from full wave simulations incorporating all material properties of the metals and dielectrics of the structures. The large index gradient has the potential to enable compact infrared diffractive and gradient index optics, as well as more exotic transformation optical media.
authors: Center for Metamaterials and Integrated Plasmonics, Department of Electrical and Computer Engineering, Duke University, Durham, North Carolina 27708, USA.
authors: Yu-Ju
authors: YJ
authors: Tsai
authors: Stéphane
authors: S
authors: Larouche
authors: Talmage
authors: T
authors: Tyler
authors: Guy
authors: G
authors: Lipworth
authors: Nan M
authors: NM
authors: Jokerst
authors: David R
authors: DR
authors: Smith
mesh_terms: D017076:Computer-Aided Design; D004867:Equipment Design; D019544:Equipment Failure Analysis; D008420:Manufactured Materials; D012031:Refractometry / Q000295:instrumentation*