Structures with periodicity in one, two or three dimensions give new options to control the properties of wave propagation and are the base for the development of novel materials and devices. The properties of those photonic crystals are quite similar to to the characteristics of electrons in crystal lattices and are hence an optical structure corresponding to the semiconductors. There is a multitude of examples of those structures in nature, for example the wings of certain butterflys or the opals. In 1987 scientific research on photonic crystals started and the fabrication was proposed. Today this topic has become a key aspect in modern optical technology. At INA our research is mainly focused on the design and implementation of photonic crystals on thin membranes for the upgrade of Fabry-Pérot filters with e.g. polarisation control.