Dielectric spheres synthesized for the fabrication of self-organized photonic crystals such as opals offer large opportunities for the design of novel nanophotonic devices. In this paper, we show that a hexagonal superlattice monolayer of dielectric spheres exhibits an even photonic band gap below the light cone for refractive indices higher than 1.93. The use of spheres with refractive index 2.9 and diameter 0.33 mu m tunes the photonic band gap to the telecommunications range (lambda= 1.55 mu m). As a practical example for the use of such a photonic band gap, we demonstrate the possibility of waveguiding light linearly through the monolayer. (c) 2006 Optical Society of America.

We demonstrate the possibility of waveguiding electromagnetic waves in a monolayer of dielectric spheres. While light is confined vertically by index guiding, a triangular superlattice monolayer of spheres was found to exhibit a photonic band gap below the light cone, thereby preventing light from propagating laterally. A gap map of this structure is presented. We propose a possible waveguide configuration that yields two non-degenerate defect modes lying within the photonic band gap. Such a structure may be particularly interesting for coupling light into self-assembled colloidal photonic crystals.

We present the concept of graded photonic crystals (GPC) and show its ability to enhance the control of light propagation. It is shown that gradual modifications of photonic crystal parameters are able to curve the path of light. This light bending which depends on the wavelength and on the incident angle is examined through parametric studies of the iso-frequency curves. We demonstrate that photonic mirages originate from the same physical principles as the usual atmospheric mirages. Two optical components based on two-dimensional GPCs presenting a super bending effect and a large beam shifting are presented.

We present a study of graded photonic crystals presenting a mirage effect. This light bending is understood through parametric studies of the isofrequency curves. We derive a model based on the effective index computation and on the Eikonal equation in order to demonstrate that photonic mirages originate from the same physical principles as atmospheric mirages. A graded photonic crystal presenting a superbending effect is proposed for designing a bent waveguide.

Disordered two-dimensional photonic crystals with a complete photonic band-gap have been investigated. Transmission and reflection spectra have been modelled for both ballistic and scattered light. The density of states and electromagnetic field profiles of disorder-induced localized states have also been calculated, for various levels of disorder. It is found that there is a threshold-like behaviour in the amount of disorder. Below the threshold, it is seen that there is a vanishing probability of disorder-induced localized states being introduced into the centre of the photonic band-gap, but that edge-states narrow the band-gap. Above the threshold, there is a non-zero probability of disorder-induced localized states throughout the photonic band-gap, and the modification of the transmission and reflection spectra due to disorder rapidly increases with increasing disorder.

Transmission and reflection of light in disordered two-dimensional photonic crystals with an incomplete photonic band-gap have been modelled for various levels of disorder. It is found that ballistic and scattered light display different behaviours as a function of the disorder parameter. For ballistic light, the dependence of the transmission coefficient on the disorder parameter exhibits a threshold-like behaviour, whereas the transmission of scattered light increases rapidly for small disorder. Unlike for photonic crystals with a complete bandgap, the minimum of the transmission for scattered light does not coincide with the centre of the photonic band-gap, and Fabry-Perot-type oscillations can be seen within the photonic band-gap.