Accurate controlling of optical phase based on metasurfaces

In recent years, a lot of new optical phenomena have been discovered based on research of metasurfaces. Among them, geometric phase modulation is one of the most attractive directions. In this paper, some innovation research works in our group on accurate controlling of optical phase based on metasurfaces have been introduced, including anisotropy in electromagnetic response and electromagnetic resonances. Based on these principles, a series of new-concept optical elements and devices have been proposed and investigated. Firstly, a gold nanorod-based CGH (Computer Generated Hologram) was realized. Experimental results show that it can work in broad bandwidth of 630 nm~1 050 nm and the maximum diffraction efficiency reaches 80% at a wavelength of 825 nm. Secondly, a silicon nanorod beam splitter was proposed and it can generate uniform 4 × 4 spot arrays with an extending angle of 59° × 59° in far field. For such device, diffraction efficiency exceeds 50% in ranges of 1530 nm~1 565 nm. At last, a polarising beam splitter was designed with reflectivity of 98.5% along long axis of nanorod, whilst transmissivity along short axis is 94.3%. More interesting, only by changing width of nanorod, we can shift peak response wavelength from 1 460 nm to 1 625 nm. Above research results show that, with advantages such as single-step nanofabrication, continuous, arbitrary, accurate and efficient phase controlling, metasurfaces have brilliant commercial prospects. We predict that metasurfaces will be applied to develop new generation of chip-scale optoelectronic components and devices with high performance. Its application fields can cover optical telecommunication, military defense, industry and consumer electronics.