Experimental realization of Weaire–Phelan foams as photonic crystals

We experimentally investigate the properties of crystalline 3D Weaire-Phelan foam struc- tures as photonic crystals. We generate templates on the computer and use direct laser writing lithography (DLW) to fabricate foam designs in a polymer material. Due to the complicated structure of the foams, conventional DLW does not offer the resolution to pro- duce systems with a stop band for telecommunication wavelengths. We use shrinkage by thermal processing to circumvent this problem and show experimentally that foam plateau border networks built in this way provide a stop-band in the range between λ = 1 − 2μm, depending on the amount of shrinkage. We also investigate the dependence of the position and strength of the stop-gap on the sample height and the solid filling fraction.