The Photonics Research Institute of the National Institute of Advanced Industrial Science and Technology (AIST), in a joint effort with Waseda University, developed a novel production technology for forming photonic nanostructures (photonic crystal structures) from titanium dioxide. The technology employs X-ray lithography methods based on synchrotron orbital radiation to deeply and precisely form a submicron-order polymeric mask. Then, liquid-phase deposition is used to faithfully deposit a tightly packed layer of titanium oxide onto the template. Finally, the template is selectively removed to obtain a photonic nanostructure.

Photonic crystals will comprise the building blocks of the photonic devices necessary for next-generation photonic networks. Most research on these crystals involves semiconductors. Such photonic devices must feature compactness, low power consumption (low insertion loss), the ability to be integrated and aligned in extensive parallel arrays, a low price tag, and easy mountability. They also must have excellent temperature characteristics, be mass producible and reliable, and allow multi-level connectivity with fiber optics and other devices.

Titanium dioxide, the material used to form these photonic crystal structures, transmits light in the wavelength of optical communication better than silicon and other semiconductors. Furthermore, the refractive index of the compound is near that of fiber optics, making it compatible with the latter. This feature translates into a much lower loss during device I/O, making titanium dioxide essential in the development of photonic devices for next-generation photonic networks. Finally, titanium dioxide has a lower coefficient of thermal expansion than semiconductors; regulating the temperature of TiO₂ devices is simple.

Energy conservation should result if the technology indeed leads to photonic crystals with better light transmittance, lower loss in connections with optical fiber, and less intensive temperature regulation requirements. The technology is also environmentally friendly because it lacks a dry etching procedure using etching gases and is inexpensive because templates are used. It will catch the attention of the industry.

The research involved with this project was made possible through funds from the Atomic Study Research Funding of the Ministry of Education, Culture, Sports, Science, and Technology based on an assessment of the Japanese Atomic Energy Commission.

The tangible results of the research were presented at the 2nd Tsukuba Technology Showcase (January 30, 2003 at the Epochal Tsukuba International Congress Center by the Science Academy of Tsukuba) and Nano Tech 2003 + Future (February 26–28, 2003 at the Makuhari Messe by NEDO, JETRO, and AIST).