Infiltration of 3d Photonic Crystals with Embedded Structures

Introduction Colloidal self-assembly has been a widely explored approach for the generation of templates for photonic band gap (PBG) structures. This route possesses the advantage of being less tedious and expensive than the alternative layer-by-layer direct fabrication techniques that have been proposed. On the other hand, self-assembly routes are at a disadvantage with regard to their inherent lack of defect control and the insufficient dielectric constants of most colloidal crystalline materials. However, researchers have addressed these disadvantages and have demonstrated or are currently working on appropriate solutions. For example, the use of patterned substrates for colloidal epitaxy has been successful in greatly reducing the inherent defects, allowing the realization of single crystals on the order of square millimeters. Also, we recently demonstrated the use of multi-photon polymerization and laser scanning confocal microscopy as a technique for the controlled defect generation within the interior of self-assembled colloidal crystals (Figure 1); this defect fabrication ability is essential to most PBGbased applications. The problem still remains, however, that these materials have insufficient dielectric constants to be of great interest as PBG materials. When also considering that it is the inverse FCC structure that has been proposed to exhibit a PBG, it becomes apparent that these colloidal crystalline-based materials are more appropriate as templates for PBG materials. The next logical step, then, would be to investigate the infiltration of these photonic crystal templates with high refractive index materials. Here, melt imbibing and electrodeposition were chosen as infiltration routes of these high-quality 3D photonics crystals with embedded waveguide structures. Replicas of these templates with good registry have been successfully generated and these procedures and results, as well as any future developments will be presented.