Devlin Robert C, Khorasaninejad Mohammadreza, Chen Wei Ting, Oh Jaewon, Capasso Federico
Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138;
Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138; University of Waterloo, Waterloo, ON N2L 3G1, Canada.
Proc Natl Acad Sci U S A. 2016 Sep 20;113(38):10473-8. doi: 10.1073/pnas.1611740113. Epub 2016 Sep 6.
Metasurfaces are planar optical elements that hold promise for overcoming the limitations of refractive and conventional diffractive optics. Original dielectric metasurfaces are limited to transparency windows at infrared wavelengths because of significant optical absorption and loss at visible wavelengths. Thus, it is critical that new materials and nanofabrication techniques be developed to extend dielectric metasurfaces across the visible spectrum and to enable applications such as high numerical aperture lenses, color holograms, and wearable optics. Here, we demonstrate high performance dielectric metasurfaces in the form of holograms for red, green, and blue wavelengths with record absolute efficiency (>78%). We use atomic layer deposition of amorphous titanium dioxide with surface roughness less than 1 nm and negligible optical loss. We use a process for fabricating dielectric metasurfaces that allows us to produce anisotropic, subwavelength-spaced dielectric nanostructures with shape birefringence. This process is capable of realizing any high-efficiency metasurface optical element, e.g., metalenses and axicons.
超表面是平面光学元件，有望克服折射光学和传统衍射光学的局限性。由于在可见光波长下存在显著的光吸收和损耗，原始的介电超表面仅限于红外波长的透明窗口。因此，开发新材料和纳米制造技术以将介电超表面扩展到可见光谱范围，并实现诸如高数值孔径透镜、彩色全息图和可穿戴光学器件等应用至关重要。在此，我们展示了以全息图形式呈现的用于红色、绿色和蓝色波长的高性能介电超表面，其绝对效率创纪录（>78%）。我们使用表面粗糙度小于1nm且光损耗可忽略不计的非晶二氧化钛的原子层沉积。我们采用一种制造介电超表面的工艺，该工艺使我们能够生产具有形状双折射的各向异性、亚波长间距的介电纳米结构。此工艺能够实现任何高效的超表面光学元件，例如超透镜和轴锥镜。
