2, Washington State University, Pullman, Washington, United States
Colloidal photonic crystals are photonic crystals made by bottom-up physical chemistry strategies from monodisperse spherical colloidal particles. The self-assembly process is leading to inherently three-dimensional structures with optical properties determined by the periodicity, induced by this ordering process, in the dielectric properties of the material. Apart from the optical properties, the nanoscopic periodicity, exemplified by SANS, can be transferred if the crystal is used as a template for depositing or removing material as e.g. vortex pinning in Nb thin films deposited on such a crystal.
The use of hollow spheres as building blocks has brought about a whole realm of unique possibilities. One, again derived from the periodicity, is the fabrication of three-dimensional hierarchical structures at the nanoscale. It is also possible to convert the hollow nanospheres to open nanorings, which can be used as templates for the unique core-shell nanoring topology. This topology leads to tunable plasmon resonances.
The best-known optical effect, though, is the photonic band gap, the range of energies, or wavelengths, that is forbidden for photons to exist in the structure. This photonic band gap is analogous to the electronic band gap of electronic semiconductor crystals. We have previously shown how with the proper photonic band gap engineering, we can insert allowed pass band defect modes and use the suppressing band gap in combination with the transmitting pass band to induce spectral narrowing of emission and improved energy transfer. We show now how with a high-quality narrow pass band in a broad stop band, it is possible to achieve photonic crystal lasing in self-assembled colloidal photonic crystals with a planar defect. In addition, with proper surface treatment in combination with patterning, we prepare for addressable integrated photonics. Finally, by incorporating a water in- and outlet, we can create optomicrofluidic structures on a photonic crystal allowing the optical probing of microreactors or micro-stopped-flow in the lab-on-an-optical-chip.