Quasiperiodic air hole arrays for broadband and omnidirectional suppression of reflection

Surfaces patterned with quasi-periodic array of sub-wavelength air holes have been studied for their effectiveness in suppressing air-substrate reflection in the wavelength range of 450–1350 nm. Superlattice structures formed by superposing two different quasiperiodic arrays with 450 nm deep holes showed reflectance of ∼2% (compared to 6% for unpatterned substrate) for all measured incidence angles up to 50° and also show very weak polarization dependence. Dense k-space of quasiperiodic array along with the graded index offered by tapered holes provide broadband,polarization independent, and omnidirectional antireflection property.