Liquid crystals as a tool for forming photonic crystals

摘要

Since the pioneering works of Yablonovitch and John, the concept of photonic crystals has attracted great attention from both fundamental and practical points of view. Different types of approaches have been taken to realize the spatial periodic structures: nanolithography techniques developed to produce semiconductors, sedimentation of monodispersed nanoscale spheres, or holographic illumination of photosensitive materials. In our work, we employed two newly discovered fascinating phenomena: particle drag effect and particle pumping effect in a liquid crystal to build the ordered colloidal structures. Combining the moving nematic-isotropic transition line with a patterned electric field can be used to move particles from one place to another. This can be used to pack particles in a certain place in an ordered periodic structure. The speed of the interface and the magnitude of the applied electric field controls the size, density and /or dielectric property of the particle that can be moved and determines those that are left behind. This capability allows us to place "defects" at particular locations in the photonic crystals constructed. Although many challenges remain before this system can be used in practical optical components, this new technique provides an excellent means of producing complex photonic crystals tailored for specific optical affects and applications.