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Colloidal Photonic Crystals Using Space -An Academic-Industrial Collaboration-

Replacing electron tubes with solid semiconductors was the most dramatic technological innovation in 20th century and opened the door for information technology. In continuing development of the 21st century, we expect for photonic crystals to replace, at least in part, prisms, diffraction gratings and optical filters. We base this expectation on the common rule of periodic structures, which form energy bands that interact with waves. In contrast with semiconductors which have atomic scale periodicity of 0.1nm, photonic crystals have periodicity of approximately 100nm and interact with photons at corresponding wavelengths [1]. Present methods of fabricating photonic crystals mostly employ sputtering process. As an example, Tohoku University in Japan developed a method called autocloning. It is based on the deposition of multilayers by a sputtering process. The periodic structures are lithographed on the substrates. The resulting multilayers have periodic structures composed of Si, SiO2 and Ta2O5. In the marketing phase, this technology was transferred to Photonic Lattice Inc. [2]. Another method to produce photonic crystals uses a colloidal crystal composed of monodispersed particles having diameters of 100 to 200nm. The crystals are prepared from colloidal dispersions [3]. Colloidal photonic crystals are attractive because growing large crystals does not require expensive equipment. Large crystals have played an important role in industrial applications of silicon and quartz. Up to now, however, the intensive development of colloidal photonic crystals has not begun, because there is still a lot of disciplinary research that must be coherently coordinated in the early phase. This research includes preparation of nano-particles and their surface control, colloidal chemistry, crystal growth, diffusion control, gel chemistry, theoretical physics, characterization of photonic properties and device applications. Inhomogeneity of the crystals prepared on the ground is another difficulty. This paper describes a process for producing colloidal photonic crystals using microgravity in space as a focal point to organize multidisciplinary research, both academic and industrial.