Hierarchically tunable phtonic bandgaps by directional photofluidization

We prepare the azopolymer-based inverse opal using silica opal as a template. The photonic bandgaps are tuned by modulation of refractive index with a novel and simple method, directional photofluidization. This strategy enables the realization of enhanced tuning range of photonic bandgaps in optically tunable photonic crystals and the integration of multiple photonic bandgaps in a optical chip.