Three-Dimensional Photonic Crystals Made from Colloids

Abstract

In this chapter the fabrication and optical properties of three-dimensional photonic crystals made from colloids has been described. Recent progress has led to the preparation of photonic crystals with a high degree of order and a low defect density. Combination with templating methods has made it possible to achieve the high refractive index contrasts needed for useful photonic applications. The use of core-shell type composite particles or anisotropic particles to tune and improve photonic properties holds great promise for future research. In order to build actual photonic devices with colloidal crystals it will be necessary to insert lattice defects with a high degree of control. This is a much more challenging task in crystals formed by self-assembly than in those made by lithographic techniques. One way of reaching this goal was recently demonstrated by writing waveguide structures into a self-assembled crystal using multi-photon polymerization in a confocal microscope.208 External control is another important requirement. Indeed, switching of photonic crystals with electric fields has been achieved by filling colloidal crystals with liquid crystals.209 These examples show that self-assembly of colloidal particles is a powerful way of fabricating three-dimensional photonic crystals.