Narrow-bandpass filter using orthogonally propagating guided-mode resonance with doubly periodic grating

A two-dimensional grating with a doubly periodic structure is proposed to provide a narrow-bandpass filter of a small aperture. The peak transmittance of 96% was obtained by numerical simulation for a
$45-\mu \mathrm{m}$
-diameter beam and an
$85-\mu \mathrm{m}$
-size filter.