Fabrication of Photonic Fractals for Millimeter Wave Control by Using Ceramic Nanoparticles

Abstract

Photonic crystals and fractals with three-dimensional dielectric structures were fabricated in order to control millimeter waves effectively by using micro-stereolithography of rapid prototyping. The photonic crystals with a diamond structure composed of alumina lattice were fabricated. The micrometer order periodic structures exhibit perfect band gaps in terahertz frequency range. The photonic fractals with the self-similar structure of dielectric medium can localize electromagnetic wave energy. Menger-sponge fractal structures composed of alumina were also fabricated. In the micro-sterereolithography process, the photo sensitive resin paste with nanosized alumina particles dispersion was spread on a substrate with 10 μm in layer thickness by moving a knife edge, and two-dimensional images of UV ray were exposed by using DMD （Digital Micro-mirror Device） with 2 μm in part accuracy. Through the layer by layer stacking process, micrometer order three-dimensional structures were formed. Dense alumina structures were obtained by dewaxing and successive sintering in an air atmosphere. The electromagnetic wave properties of these samples were measured by using a terahertz spectroscopy device. The propagation and localization behavior of THz waves in photonic crystals and fractals composed of alumina will be reported. In near future, millimeter wave in a terahertz frequency range will be expected to apply for various types of novel sensors which can detect gun powders, drugs, bacteria in foods, micro cracks in electric devices, cancer cells in human skin and other physical, chemical and living events. To control millimeter waves in terahertz frequency range, micrometer order electromagnetic devices of photonic crystals and fractals for cavities, filters and antennas would be used.