Self-assembly route for photonic crystals with a bandgap in the visible region

Abstract

Three-dimensional photonic crystals, or periodic materials, that do not allow the propagation of photons in all directions with a wavelength in the visible region have not been experimentally fabricated, despite there being several potential structures and the interesting applications and physics that this would lead to. We show using computer simulations that two structures that would enable a bandgap in the visible region, diamond and pyrochlore, can be self-assembled in one crystal structure from a binary colloidal dispersion. In our approach, these two structures are obtained as the large (Mg) and small (Cu) sphere components of the colloidal analogue of the MgCu(2) Laves phase, whose growth can be selected and directed using appropriate wall patterning. The method requires that the particles consist of different materials, so that one of them can be removed selectively after drying (for example, by burning or dissolution). Photonic calculations show that gaps appear at relatively low frequencies indicating that they are robust and open for modest contrast, enabling fabrication from more materials.

Hiding in Plain View: Colloidal Self-Assembly from Polydisperse Populations

“…Various AB 2 phases are well known in binary mixtures of hard spheres [38][39][40][41][42][43]. For example, the AlB 2 structure is a preferred crystal phase for binary mixtures with a size ratio of the smaller to larger particles between approximately 0.4 and 0.6 [39] and occurs in gem opals [40,41], while the MgCu 2 phase can be templated by walls [43].…”

High Frequency Acoustics in Colloid-Based Meso- and Nanostructures by Spontaneous Brillouin Light Scattering

“…When the light is reflected many times between the mirrors, the reflected beams interfere. Only light that fulfills the equation 88) with m being an integer and n F P being the refractive index inside the FP, and θ F P being the angle between the light in the FP and the normal to the mirrors, is transmitted losslessly due to constructive interference. Thus usually the interferometry is performed by moving one of the mirrors, there is just air between the mirrors (The other possibility would be to vary n during a measurement.).…”

“…Their propagation is forbidden at 'Bragg' frequencies or wavelengths commensurate with the lattice constant, which for sub-micrometer particles is comparable with the wavelength of the visible light. Synthetic opals from these particles can exhibit dual, i.e., hypersonic phononic and photonic [87,88] band gaps allowing for acousto-optical interactions. [89] Moreover, the design of submicron particles that can act as strong localized resonant elements in an appropriate matrix provides the possibility for additional gaps well below the Bragg frequency, termed hybridization gaps (cf.…”

In situ observation of nanoparticle ordering at the air-water-substrate boundary in colloidal solutions using x-ray nanobeams

“…[2][3][4] To deposit the nanoparticle layer on top of the substrate, several methods are available, e.g., vacuum deposition 1,5 and solution casting. Solution casting allows nanostructuring of large-area two-dimensional ͑2D͒ thin films with specific morphology, offering the possibility to design 2D or threedimensional photonic crystals.…”