Toward photonic crystal based spatial filters with wide angle ranges of total transmission

Spatial filters with steep switching between wide ranges of total transmission and total reflection can be obtained by using two-dimensional dielectric photonic crystals, which are a few wavelengths thick. The guidelines for engineering bandpass and bandstop filters are given. The flatness of isofrequency contours that are localized around a periphery point of the first Brillouin zone is a necessary but insufficient condition for the existence of wide angle ranges of total transmission at intermediate and large angles of incidence. Such ranges that are wider than 20 degrees are demonstrated.