We have directly observed the Anderson localized wave functions in three dimensions in a new class of photonic band gap systems. Such systems are networks made of one-dimensional waveguides. By adopting a simple scattering geometry in a unit cell, we are able to obtain large photonic band gaps. In the presence of defects or randomness, we have systematically studied the structures of transmission and the localized wave functions inside a gap. The effects due to absorption are investigated. Excellent quantitative agreements between theory and experiments have been obtained.

• Received 13 May 1998

DOI:https://doi.org/10.1103/PhysRevLett.81.5540