  We show that slightly polydisperse disordered 2D foams can be used as a
self-assembled template for isotropic photonic band gap (PBG) materials for
transverse electric (TE) polarization. Calculations based on in-house
experimental and simulated foam structures demonstrate that, at sufficient
refractive index contrast, a dry foam organization with threefold nodes and
long slender Plateau borders is especially advantageous to open a large PBG. A
transition from dry to wet foam structure rapidly closes the PBG mainly by
formation of bigger fourfold nodes, filling the PBG with defect modes. By
tuning the foam area fraction, we find an optimal quantity of dielectric
material, which maximizes the PBG in experimental systems. The obtained results
have a potential to be extended to 3D foams to produce a next generation of
self-assembled disordered PBG materials, enabling fabrication of cheap and
scalable photonic devices.
