Abstract

The idea of the angular, or equivalently – spatial filtering, is based on a selective diffraction of the angular components of the light propagating through a double-periodic photonic structure: the angular components of the incident light at a resonance with the transverse q_r and longitudinal q_l structure lattice vectors diffract efficiently and are removed from the zero-diffraction order T₀ of the transmitted beam. In case of two-dimensional, axisymmetric, filtering an additional effect was reported as well: the filtered out angular components re-diffract back from the first T_−1,+1 order- to the zeroth-order T₀ diffraction component, specifically, to the near-zero propagation angles. This results in enhancement of the low angle beam components, which comprises a beam collimation effect [1].

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