Abstract
The gradient and reversible atomic-engineered metamaterials (GRAM) method offers a distinct approach to active metamaterials through precise atomic-manipulation, essential for enhancing multilevel programmability. GRAM leverages phase transitions to control the arrangement of foreign atoms within the host material, enabling continuous, multitiered transformations at the atomic scale. Consequently, solid metamaterials achieve nonbinary tunability with reversible modulation of multiple optical states. This method’s adaptability in postsynthesis modifications addresses existing challenges in tuning mechanisms for solid metaoptics. By dynamically controlling noble metal atoms through thermal modulation, GRAM enables flexibility in altering the refractive index and device structures. This adaptability has potential applications in imaging, computing, and optical camouflage, providing a versatile strategy for enhancing performance and overcoming limitations in current solid material tuning techniques. Metamaterial has been captivated a popular notion, offering photonic functionalities beyond the capabilities of natural materials. Its desirable functionality primarily relies on well-controlled conditions such as structural resonance, dispersion, geometry, filling fraction, external actuation, etc. However, its fundamental building blocks—meta-atoms—still rely on naturally occurring substances. Here, we propose and validate the concept of gradient and reversible atomic-engineered metamaterials (GRAM), which represents a platform for continuously tunable solid metaphotonics by atomic manipulation. GRAM consists of an atomic heterogenous interface of amorphous host and noble metals at the bottom, and the top interface was designed to facilitate the reversible movement of foreign atoms. Continuous and reversible changes in GRAM’s refractive index and atomic structures are observed in the presence of a thermal field. We achieve multiple optical states of GRAM at varying temperature and time and demonstrate GRAM-based tunable nanophotonic devices in the visible spectrum. Further, high-efficiency and programmable laser raster-scanning patterns can be locally controlled by adjusting power and speed, without any mask-assisted or complex nanofabrication. Our approach casts a distinct, multilevel, and reversible postfabrication recipe to modify a solid material’s properties at the atomic scale, opening avenues for optical materials engineering, information storage, display, and encryption, as well as advanced thermal optics and photonics.