Extraordinary Figure‐of‐Merit of Magnetic Resonance from Ultrathin Silicon Nanohole Membrane as All‐Dielectric Metamaterial

Metamaterial allows novel nanophotonic applications such as negative permeability, negative refractive index, and near‐zero index. In particular, all‐dielectric metamaterials recently create new opportunities for manipulating electromagnetic fields, taking full advantage of low‐loss, bandwidth enhancement, and isotropic responses. Here a silicon dielectric metamaterial is reported in near‐infrared region, exhibiting extraordinarily figure‐of‐merit, defined by sensitivity (resonance shift/refractive index change) over full width at half maximum, from magnetic resonance shift depending on index changes of surrounding medium. This silicon dielectric metamaterial comprises subwavelength nanohole arrays in a square lattice on an ultrathin amorphous silicon membrane. The ultrathin silicon nanohole membrane is fabricated on a glass wafer by using e‐beam lithography, silicon reactive ion etching, and hydrogen fluoride wet etching. This all‐dielectric metamaterial successfully demonstrates exceptional figure‐of‐merit of 29, which is 7.6 times higher than those values of conventional metamaterials. This novel metamaterial enables not only the label‐free detection of chemical and biological molecules with different mass concentrations but also the in situ reaction monitoring of biochemical molecules.