Manipulating Colloidal Crystallization for Photonic Applications: From Self-Organization to Do-it-Yourself Organization

Abstract

Photonic crystals are regular three-dimensional (3D) structures with which the propagation and spontaneous emission of photons can be manipulated in new ways if the feature sizes are roughly half the wavelength and the coupling with the electromagnetic radiation is sufficiently strong. ‘Early’ speculation on these new possibilities can be found in the Refs.1–4 A more recent overview can be found in Ref.5 and, of course, the other chapters in this book. A useful analogy to guide thinking about the properties and the applications of photonic crystals is the propagation of electrons in a semiconductor in comparison to the propagation of photons scattered by a regular 3D dielectric material. An example is the possibility of opening up a region of energy, a photonic band gap, for which the propagation of photons is forbidden, in analogy to the electronic band gap present in semiconductors. However, there are also important differences; for instance, the scattering of photons cannot be described well by scalar wave equations because the polarization of light cannot be neglected. Most theoretical and experimental work for visible light applications have until now focused on pure dielectric structures, interestingly, recent calculations have shown that metallo-dielectric structures should also be considered as having very interesting photonic properties in the visible, including, if one neglects absorption, a complete band gap.6–8 And even with absorption taken into account, it seems that for relatively thin photonic crystals most of the interesting optical properties remain.8