Reversible Thermally Driven Phase Change of Layered In₂Se₃ for Integrated Photonics

Two-dimensional In₂Se₃, an unconventional phase-change material, has drawn considerable attention for polymorphic phase transitions and electronic device applications. However, its reversible thermally driven phase transitions and potential use in photonic devices have yet to be explored. In this study, we observe the thermally driven reversible phase transitions between α and β' phases with the assistance of local strain from surface wrinkles and ripples, as well as reversible phase changes within the β phase family. These transitions lead to changes in the refractive index and other optoelectronic properties with minimal optical loss at telecommunication bands, which are crucial in integrated photonic applications such as postfabrication phase trimming. Additionally, multilayer β'-In₂Se₃ working as a transparent microheater proves to be a viable option for efficient thermo-optic modulation. This prototype design for layered In₂Se₃ offers immense potential for integrated photonics and paves the way for multilevel, nonvolatile optical memory applications.