Characterization of Photonic Colloidal Single Crystals by Microradian X‐ray Diffraction

Abstract

Photonic crystals (PCs) can provide unprecedented control over both the emission and the propagation of light, allowing important applications in, for example, infrared telecommunications. [1–3] However, fabrication and characterization of PCs is challenging owing to the large refractive-index contrast that is needed to open up a photonic bandgap. [4] Here we demonstrate that microradian X-ray diffraction can be used to characterize various (inverse) PCs with lattice spacings as large as 1.3 lm at different stages of their fabrication. We have even fabricated non-close-packed (non-cp) PC structures by selfassembly of colloidal microspheres in an external electric field. Inverse PCs have been obtained by infiltration of the colloidal-crystal templates with amorphous silicon. The size of the colloidal particles allows us to characterize the internal 3D structure of these crystal templates in both real and reciprocal space. PCs are structures in which the refractive index varies periodically in space on a length scale comparable to the wavelength of light. [3] If the refractive-index contrast is large enough,PCs can have a photonic bandgap, which is the photonic analogue of the electronic bandgap in semiconductors. [5–7] A