Papers by Keyword: Diamond Structure

Abstract: To fabricate artificial crystals with any structure from monosized spherical particles, we have so far manufactured a three-dimensionally particle assembling system with a combination of pick-and-place robotic manipulation and inter-particle laser welding. In the present study, we aimed to assemble large-scale artificial crystals of polyethylene (PE) particles by mean of the new system. In this method, an optimization of the laser welding conditions was indispensable for the strong bonding with maintaining the shape of particles. Thus, the two-particle welding tests were preliminarily conducted. On the basis of this result, we successfully assembled the large-scale artificial crystals with diamond structure from the PE -ceramic or -carbon composite particles. In order to discuss applicability of the obtained crystals to terahertz (THz) wave photonic crystals, the transmittance spectrum of the crystals was evaluated by a THz wave time domain spectroscopy. The PE-ceramic particle crystal presented an ideal photonic band gap which perfectly agreed with the theoretical one.

Abstract: The three-dimensional (3D) photonic band gap material is a material that there exists a full photonic band gap in which waves are forbidden to propagate whatever the polarization or the direction of propagation. In order to obtain photonic bandgap in lower range, we focus on the fabrication of PBG materials of diamond structure with TiO2 powder mixed with SiO2. The inverse epoxy structure with periodic diamond lattices in millimeter order has been fabricated by stereolithographic rapid prototyping. TiO2 slurry was filled into the epoxy structure and then cold isostatic pressing was applied. After sintering at 700K for 5hrs, the epoxy was burnt out and the designed structure was maintained perfectly. The calculated band diagram shows that there exists an absolute photonic band gap for all wave vectors. The measurement of transmission from 10 to 20 GHz in <100> direction shows that a complete band gap is formed at about 14.7-18.5 GHz. The magnitude of the maximum attenuation is as large as 30 dB at 17 GHz.