A analysis group at POSTECH, led by Professor Junsuk Rho (Departments of Mechanical Engineering, Chemical Engineering, Electrical Engineering, and the Graduate College of Convergence Science and Know-how), together with M.S./Ph.D. college students Seokwoo Kim, Joohoon Kim, Kyungtae Kim, and Minsu Jeong (Division of Mechanical Engineering), has developed a novel multidimensional sampling idea to beat the constraints of flat optics. Their research not solely identifies the constraints of standard sampling theories in metasurface design but in addition presents an revolutionary anti-aliasing technique that considerably enhances optical efficiency. Their findings had been printed in Nature Communications.
Flat optics is a cutting-edge expertise that manipulates mild on the nanoscale by patterning ultra-thin surfaces with nanostructures. In contrast to conventional optical techniques that depend on cumbersome lenses and mirrors, flat optics allows ultra-compact, high-performance optical units. This innovation is especially essential in miniaturizing smartphone cameras (decreasing the “digital camera bump”) and advancing AR/VR applied sciences.
Metasurfaces, one of the promising functions of flat optics, depend on a whole lot of thousands and thousands of nanostructures to exactly pattern and management the section distribution of sunshine. Sampling, on this context, refers back to the strategy of changing analog optical indicators into discrete knowledge factors — much like how the human mind processes visible data by quickly capturing a number of photos per second to create steady movement notion. Nevertheless, conventional sampling strategies include challenges. When the sampling charge is just too low, aliasing artifacts happen, resulting in distorted photos and optical inefficiencies. A widely known instance is the wagon-wheel impact, the place a spinning wheel in a video seems to maneuver backward or freeze as a result of inadequate body charges. This aliasing situation is a serious limitation in metasurface design, considerably decreasing optical effectivity and precision.
For many years, researchers have relied on the Nyquist sampling theorem to foretell and mitigate aliasing. Nevertheless, the POSTECH group found that Nyquist’s theorem, whereas helpful for digital sign processing, doesn’t totally account for the optical complexities of metasurfaces. Whereas Nyquist idea successfully defines frequency limits for digital sign processing, it fails to precisely predict or forestall optical distortion in metasurfaces, which should account for each the advanced nanostructure of metasurfaces and the wave nature of sunshine.
To handle this limitation, the group developed a brand new multidimensional sampling idea that includes each the two-dimensional lattice construction of metasurfaces and the wave properties of sunshine. Their analysis, for the primary time, revealed that the geometric relationship between a metasurface’s nanostructured lattice and its spectral profile performs a vital position in figuring out optical efficiency. By adjusting the lattice rotation and integrating diffraction components, the group launched an anti-aliasing technique that minimizes noise and enhances mild management. Utilizing this method, they efficiently decreased optical noise throughout a broad spectrum — from seen mild to ultraviolet wavelengths — and demonstrated high-numerical-aperture (NA) metalenses and wide-angle meta-holograms functioning within the ultraviolet regime. This research not solely redefines the theoretical framework for optical metasurfaces but in addition relaxes fabrication constraints, making high-resolution ultraviolet and high-numerical-aperture metasurfaces extra possible.
Professor Junsuk Rho emphasised the importance of their discovery: “This analysis opens new potentialities for next-generation flat optical units, together with high-NA metalenses and wide-angle meta-holograms. Our newly developed sampling idea is extremely versatile, spanning wavelengths from microwaves to excessive ultraviolet. Brief-wavelength ultraviolet optics require extraordinarily exact fabrication, making analysis on this space extremely difficult. Nevertheless, our findings considerably ease these fabrication calls for, unlocking new alternatives in ultraviolet metasurfaces.”
This analysis was supported by POSCO, Samsung Electronics, the Ministry of Science and ICT, and the Nationwide Analysis Basis of Korea.
