Designing infrared phase change materials for colorful infrared transmittance modulators

Abstract

Colorful infrared transmittance modulators (CITM) have important applications in many emerging optical fields. However, there are no rich colors in the existing infrared-transmittance modulators. The selective reflection-enhanced Fabry-Perot (FP) cavities in rich colors cannot obtain transmittance modulation performance owing to the use of metallic reflective layers. Here, we design an asymmetric FP cavity with high-optical-contrast infrared phase change materials as the reflective layer (named as “IRPCM” cavity), achieving a combination of infrared transmittance modulation and desired colors. As a proof-of-concept, our prepared IRPCM cavity composed of ZnS/GeTe not only has infrared transmittance modulation performance (66%, 3–5 μm) much greater than that of the traditional Ge2Sb2Te5 film (38%), but also has colors. By combining theoretical calculations with experiments, we show that the high transmittance modulation performance of GeTe results from its small atomic composition and intrinsic vacancy-free structure. Based on the new insights, we propose the design principles of IRPCM and outline the materials map. The results show that besides GeTe, GeSe0.75Te0.25 and Ge4Sb0.5Bi0.5Te5 are also IRPCM candidates. Therefore, this study provides new IRPCMs for solving the problem of integrating colors with infrared-transmittance modulation in a thin film.