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 VO(2) 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 mum 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 VO(2) which are measured by infrared ellipsometry.