Nanophotonic Phase Change Material Devices for Tunable High-Purity Color Filters

Active thin-film coating-based reflective color displays have versatile applications including image sensors, camouflage devices, spatial light modulators, and intelligent windows. However, generating high-purity colors using such coatings has posed a challenge. Here, we will discuss high-purity color generation using an ultralow-loss phase change material (Sb2S3)-based tunable aperiodic distributed Bragg reflector (A-DBR). By adjusting the periodicity of the adjacent layers of A-DBRs, we realize a narrow photonic bandgap with high reflectivity to generate high-purity orange and yellow colors. Moreover, we experimentally demonstrate multistate tunable colors through external optical and thermal stimuli. Unlike conventional nano thin-film coatings, our proposed approach offers an irradiance-free, narrowband, and highly reflective color band, achieving high color purity through the supression of reflections in off-color bands.