The idea of the angular, or equivalently - spatial, filtering by photonic crystals (PhCs) is based on a selective diffraction of the light propagating through the double-periodic photonic structure. The angular components of the incident light at a resonance with the transverse and longitudinal periodicities of the structure diffract efficiently and are removed from the zero-diffraction order of the transmitted beam. On the other hand, the propagation of the angular components that are out of the resonances is unaffected. Therefore, the angular/spatial filtering can be obtained by a suitable geometry of the PhCs. This idea already proven itself as a useful alternative to conventional spatial filtering techniques, and is being implemented in several applications, for instance for intracavity angular filtering in microlasers [1]. © 2019 IEEE.