A Simplified Approach for Obtaining Optical Properties of VO2 Thin Films, and Demonstration of Infrared Shape-Shifting Devices

Micrometer-sized VO2-based devices with integrated resistive heaters of different configurations are fabricated. Quality of the VO2 films is confirmed by measuring the characteristic drop in transmittance and negative differential emissivity for these films. A two-interface model for optical transmittance, reflectance, and absorbance is presented. This method and analytic model presents an advantage over most typically used approaches in that it does not require direct measurements of the material's optical constants to estimate transmittance. By combining the substrate and the VO2 film into one layer with a reduced optical admittance, the two-interface model is reduced to a single-layer model. Moreover, the present work demonstrates the implementation of the developed VO2-based devices in adaptive camouflage and shape-converting applications. Electrical pulses are used to program different emissivity states to convert geometric shapes inside a fully integrated VO2-based electro-optical window. This results in the reconfiguring of thermal images to either create new shapes, or shift from one to another.