Optical metasurfaces comprise of ultrathin two-dimensional (2D) metal/dielectric phase shifters with subwavelength features (also referring to meta-atoms). With rigorous design on the size, shape and location of meta-atoms in the reflect- or transmit-arrays, it can precisely tailor the scattering properties of light which is different from the incident beam and the characteristics of interaction between incident light and metasurfaces can be engineered to realize many functions of traditional bulky elements such as lenses, gratings, mirrors, waveplates and etc. Early works motivated by ultrathin metallic structures to resonant with the incidence of electromagnetic field to manipulate the light with resonant or geometric phase. However, the material loss significantly limits the performance of plasmonic metasurfaces, in particular in the transmission mode of single layer structures. Dielectric geometric phase based on half wave plate is able to shape wavefronts but their challenging issue lies in the difficulty of simultaneous realization of high efficiency and large deflection angle due to the coupling between the elements. The coupling between neighboring meta-atoms is also remarkable in the case of Huygens’ metasurfaces, which heavily degrades its performance. The drive to make highly efficient dielectric metasurfaces has been the mandatory prerequisite for the futuristic development of planar metadevices and systems.
To address those challenging issues, I will introduce our latest development on high transmission efficiency metasurfaces operating in near UV range using a transition metal oxide of higher band gap energy than titanium dioxide and demonstrate its various applications.