Colloidal photonic crystal architectures for advanced light management applications

A brief introduction to photonic crystals and colloidal photonic crystals in particular is given followed by an outline of the two main methods of forming colloidal photonic crystals employed by the authors' research team-controlled evaporation (CE) which leads to face centred cubic structures such as are found in natural opal gemstones and the Langmuir-Blodgett (LB) method which leads to more disordered materials. The ability to control deposition on a layer-by-layer (LbL) level using the LB approach is highlighted by a discussion of the fabrication of a so-called AB heterostructured colloidal photonic crystal, made from spheres of two different sizes. Following this the use of atomic layer deposition (ALD) to infill 3-D colloidal photonic crystals in order to be able to tune the refractive index contrast in the material is described, using as an example our work on the fabrication and characterisation of GaAs infilled colloidal photonic crystals and inverted GaAs photonic crystals that were made via infilling followed by removal of the silica host spheres. The importance of choosing the correct value for the refractive index of the infill material is highlighted and an optical Brillouin zone constructed using a free software package (MIT) which accounts for some of the observed Bragg reflections. Finally, some examples are presented which demonstrate the potential of the use of these and other similar materials for a range of novel optical applications.