Phase Characterization of Reflectarray Elements at Infrared

The feasibility of a square-patch reflectarray element design is demonstrated at a frequency of 28.3 THz in the infrared (10.6 micrometer free-space wavelength) for the first time. Fabrication of arrays of various patch sizes was performed using electron-beam lithography, and the reflected phase as a function of patch size was characterized using an infrared interferometer. A numerical model for the design of these reflectarray elements was developed incorporating measured values of frequency-dependent material properties, and a comparison of computed and measured phase shows close agreement.