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Manipulating electromagnetic waves by controlling their amplitude, phase, and polarization is essential for implementing numerous exciting applications and consumer-level devices. However, conventional optical elements acquire phase accumulation through the propagation effect, which results in bulky optical devices and thus hinders their further miniaturization. In recent years, the remarkable development of nanofabrication technologies enabled the emergence of artificially engineered ultrathin structures called metasurfaces that provide a fascinating boulevard to tailor the field distribution of electromagnetic waves at the micron scale. Metasurfaces are ultrathin optical components with an array of low-loss, precisely engineered building blocks that exhibit the unprecedented capability of manipulating electromagnetic waves. However, the ever-growing demand for miniaturized multifunctional optical devices requires the design and implementation of ultra-compact devices capable of integrating multiple functionalities into a single structure. Here, in this work, we proposed a single-layered all-dielectric multifunctional metadevice capable of controlling the wavefront of the incident light and exhibiting multiple optical phenomena in the ultraviolet domain. The presented meta-device exploits the spin-decoupling technique and interleaves the propagating and Pancharatnam-Barry (PB) phases to encode the multiple functionalities in it. Our meta-device consists of a super-cell having rectangular nanoantennas of silicon nitride (Si3N4) material arranged on a sapphire (Al2O3) substrate. The proposed meta-device generates three focused spots at the specified focal plane but at different positions by impinging the linearly polarized light. The presented design technique may provide an exciting roadmap toward developing and implementing multifunctional meta-devices, which will find several applications in medicine, communication, and integrated photonics.
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