  Recently, disordered photonic media and random textured surfaces have
attracted increasing attention as strong light diffusers with broadband and
wide-angle properties. We report the first experimental realization of an
isotropic complete photonic band gap (PBG) in a two-dimensional (2D) disordered
dielectric structure. This structure is designed by a constrained-optimization
method, which combines advantages of both isotropy due to disorder and
controlled scattering properties due to low density fluctuations
(hyperuniformity) and uniform local topology. Our experiments use a modular
design composed of Al2O3 walls and cylinders arranged in a hyperuniform
disordered network. We observe a complete PBG in the microwave region, in good
agreement with theoretical simulations, and show that the intrinsic isotropy of
this novel class of PBG materials enables remarkable design freedom, including
the realization of waveguides with arbitrary bending angles impossible in
photonic crystals. This first experimental verification of a complete PBG and
realization of functional defects in this new class of materials demonstrates
their potential as building blocks for precise manipulation of photons in
planar optical micro-circuits and has implications for disordered acoustic and
electronic bandgap materials.
