Abstract In this study, a tunable all-dielectric metalens (TADM) is presented. Focal lengths of incident wavelengths could be tuned by vertically changing the distance between two metalens layers or changing the incident angle of light. By changing the distance between two metalens layers from 5?μm to 32?μm, the tuning ranges of focal lengths are 21.29?μm, 22.77?μm, 22.75?μm, and 22.28?μm for the incident wavelengths of 660?nm, 580?nm, 530?nm, and 480?nm, respectively. The variation in tuning ranges of focal lengths is less than 1?μm. By changing the incident angle of light less than 1°, the tuning ranges of focal lengths are 13.35?μm, 12.87?μm, 15.81?μm, and 17.83?μm for the incident wavelengths of 660?nm, 580?nm, 530?nm, and 480?nm, respectively. The variation in tuning ranges of focal lengths is less than 4.5?μm. TADM exhibits excellent merits in the entire visible spectrum, including the characterizations of achromatism, ultrahigh resolution, and tunability. Such results are very suitable for miniaturized imaging devices, such as lens of smart phones, flexible displays, ultra-lightweight VR/AR glasses, and communication systems with multi-color-channel functionalities.
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