Capping metallic nanohelixes with SiO 2 nanohelixes to enhance broadband and wide-angle light extinction.

In this work, an SiO ₂ nanohelix array is obliquely deposited upon a metal nanohelix array as an index matching layer to enhance light extinction. Firstly, an SiO ₂ -Ag nanohelix array is fabricated with stronger light extinction than the Ag nanohelix array over wavelengths from 300 nm to 1000 nm at normal incidence. Next, the SiO ₂ -Al-Ag nanohelix array is fabricated; it exhibits broadband and wide-angle light extinction that is stronger that reported for the Al-Ag nanohelix array. The unpolarized extinctance exceeds 90% over wavelengths from 400 nm to 2000 nm and angles of incidence from 0° to 70°.