Films with Tunable Graded Refractive Index Consisting of Spontaneously Formed Mesoporous Silica Nanopinnacles

Shin Kitamura, Yosuke Kanno, Masatoshi Watanabe, Masahiko Takahashi, Kazuyuki Kuroda, Hirokatsu Miyata

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

Coatings with surfaces packed with pointed projections with subwavelength sizes are known as "moth-eye", whose graded index structure gives superior antireflection (AR) properties with a small dependence on wavelength and incident angle. However, the optical interface between the AR coating and a substrate still causes reflection, unless the refractive index of the coating is matched to that of the substrate. Here, we show a new AR coating with both graded and tunable refractive index, which completely eliminates distinct optical interfaces. The coating is made of a mesoporous silica film, whose surface is spontaneously converted to an assembly of pointed nanostructure by reactive ion etching, and its refractive index is matched universally to that of a substrate by controlled incorporation of titanium dioxide into the mesopores. This AR coating enables universal ultralow reflection on a substrate over the index range from 1.2 to 1.8 and will be applied widely in practical optics. (Figure Presented).

Original languageEnglish
Pages (from-to)47-52
Number of pages6
JournalACS Photonics
Volume1
Issue number1
DOIs
Publication statusPublished - 2014 Jan 15

Keywords

  • antireflection
  • film
  • index matching
  • mesoporous
  • moth-eye
  • subwavelength structure

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Biotechnology
  • Atomic and Molecular Physics, and Optics
  • Electrical and Electronic Engineering

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