Bandgap tuning of photonic crystals by polymer swelling

Polymer swelling is studied as a novel method for bandgap tuning of photonic crystals (PCs). Crosslinked polymers swell in the presence of solvents, thereby increasing their volume and changing their refractive index. Consequently, the lattice constant and the refractive index of a polymer PC is modified by swelling and leads to a shift of the optical bandgap.We present experimental studies of swelling of one-dimensional PCs and theoretical calculations of swelling of three-dimensional PCs. It is shown that the frequencies of the optical bandgap of a polymer PC is shifted by about 10% when exposed to a solvent-nitrogen gas mixture at 80% of the solvent saturation pressure.