Infiltration of high-dielectric-constant materials into porous photonic crystals has become a standard way to enhance the optical performance of these optical lattices. In the majority of cases, periodic 3D structures are employed as matrices to host all types of high-refractive-index materials. The driving force behind this area of research has been the desire to attain highly symmetric crystals with a strong modulation of the refractive index, since this would lead to the opening of the full photonic bandgap, that is, spectral ranges for which propagation is forbidden, irrespective of the crystalline direction.
The periodic alternation of layers of nanoparticles of different composition gives rise to novel optical materials that combine high reflectivity at the desired wavelength range with a large and accessible porosity. This latter feature allows the structure to be infiltrated with guest compounds that can enhance the performance of the multilayer as colored mirrors or provide the structure with multiple functionalities.
New work published by Hernán Míguez et al. at the Instituto de Ciencia de Materiales de Sevilla shows how gallium arsenide, a high-refractive-index semiconductor, is infiltrated for the first time into the void network of a nanoparticle multilayer using a gas-phase synthetic approach. The high uniformity achieved and the control over the amount loaded yields a new photonic material displaying wider and more intense reflectance peaks in the visible and near-infrared regions. The optical response of the hybrid ensemble can be accurately tuned through the number of infiltration cycles performed. This method is generic and can be extended to any other III–V- or IV-type semiconductor that can be synthesized from the gas phase.