Experimental demonstration of tunable phase in a thermochromic infrared-reflectarray metamaterial

For the first time, a tunable reflected phase reflectarray is demonstrated in the thermal infrared. This is done using thermochromic VO2 square-patch elements in a reflectarray metamaterial configuration. A sixty degree change in reflected phase is measured using a Twyman-Green interferometer, and FTIR measurements show that the resonance reflection minima shifts from 9.2 to 11.2 mu m as the sample is heated from 45 through 65 degrees C. These results are in agreement with finite-element method simulations using the optical properties of VO2 which are measured by infrared ellipsometry. (C) 2010 Optical Society of America