Dielectric metasurfaces are promising optical components due to lossless nature and broad functionality including lenses, polarizers, waveplates, routers, holography, and so on. These metasurfaces consist of meta-atoms made of transparent and high index materials at the designed wavelength. Silicon (n = 4 ~ 3.5 at 700 nm ~ 1 μm) is very promising material at the near-infrared range, although it has absorption in the visible region. In addition, as the band gap increases, dielectric constant decreases so it requires much higher aspect ratio in the visible range, which makes fabrication difficult. Meta-atoms consists of a high-aspect ratio pillars, posts or holes with circular, rectangular, or polygonal two-dimensional shape. Since subwavelength feature size is required, electron beam lithography (EBL) is essential, including production of mask reticle for stepper or nanoimprint molds. However, complicated and massively-parallel pattern of metafurfaces for enough functionality makes EBL difficult through both increase of exposure data file size and lengthening of exposure time.
© 2019 Japan Society of Applied Physics, The Optical Society (OSA)PDF Article