From colour fingerprinting to the control of photoluminescence in elastic photonic crystals

In photonic crystals (PCs), strong scattering and destructive wave interference lead to a modi. cation of the photon density of states in particular energy regions and along certain crystallographic directions(1,2). The consequences of this range from suppression and enhancement of luminescence(3-7) to narrow-band bright reflections useful for colour sensors(8,9), displays(10) and tuneable filters(11-14). Here we demonstrate large-area films of porous elastomeric photonic crystals (EPCs) that are compressively - decompressively cycled to reversibly shift the position of the photonic band structure over a large wavelength range. Owing to their low compressive threshold, such porous EPCs can be used for imaging that is pressure and time sensitive, for example, to obtain colour fingerprints with high accuracy. Furthermore, by incorporating luminescent PbS quantum dots in the EPCs, the photonic stop-gap can be tuned through the near-infrared (NIR) quantum dot photoluminescence (PL) peak. Thereby we demonstrate a tuneable modi. cation of photonic characteristics, including the suppression and enhancement in emission and dynamic modi. cation of luminescence lifetimes.