Aperiodic Bragg Reflectors for Tunable High-Purity Structural Color Based on Phase Change Material

Abstract

Tunable 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 have posed a challenge. Here, we reveal high-purity color generation using an ultralow-loss phase change material (Sb 2 S 3 )-based tunable aperiodic distributed Bragg reflector (A-DBR). By strategically 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. In particular, we demonstrate an A-DBR with a large photonic bandgap tunability by changing the structural phase of Sb 2 S 3 layers from amorphous to crystalline. Moreover, we experimentally tailor multistate tunable colors through external optical stimuli. Unlike conventional nano thin-film coatings, our proposed approach offers an irradiance-free, narrowband, and highly reflective color band, achieving exceptional color purity by effectively suppressing reflections in off-color bands.

Tunable Near-Infrared Transparent Bands Based on Cascaded Fabry–Perot Cavities Containing Phase Change Materials

“…In the intermediate phase, Sb2S3 can be regarded as a mixture of amorphous and crystalline molecules with different proportions. Hence, the relative permittivity of Sb2S3 under intermediate phase 𝜀 can be calculated by the effective medium approach, i.e., [50,51]: It is known that Sb 2 S 3 is a kind of lossless phase-change material at near-infrared wavelengths [49]. The refractive index of Sb 2 S 3 can be flexibly tuned by its crystalline fraction [50,51].…”

“…Hence, the relative permittivity of Sb2S3 under intermediate phase 𝜀 can be calculated by the effective medium approach, i.e., [50,51]: It is known that Sb 2 S 3 is a kind of lossless phase-change material at near-infrared wavelengths [49]. The refractive index of Sb 2 S 3 can be flexibly tuned by its crystalline fraction [50,51]. By controlling the power density of a continuous-wave laser, the crystalline fraction can be changed from 0% to 100% [50].…”

“…The refractive index of Sb 2 S 3 can be flexibly tuned by its crystalline fraction [50,51]. By controlling the power density of a continuous-wave laser, the crystalline fraction can be changed from 0% to 100% [50]. According to the experimental data in Ref.…”

“…In the intermediate phase, Sb 2 S 3 can be regarded as a mixture of amorphous and crystalline molecules with different proportions. Hence, the relative permittivity of Sb 2 S 3 under intermediate phase ε int can be calculated by the effective medium approach, i.e., [50,51]:…”

“…It is known that both Na films [47] and Sb 2 S 3 films [61] can be fabricated by the spin-coating technique. In addition, the crystalline fraction of Sb 2 S 3 film can be flexibly controlled by the power density of a continuous-wave laser [50]. Therefore, the tunable near-infrared transparent band would be achieved using the spin-coating and continuous-wave lasing techniques.…”