Appl Phys A (2010) 100: 981–985 DOI 10.1007/s00339-010-5906-7 INVITED PAPER Fabrication of flexible photonic crystal using alumina ball inserted Teflon tube Yoshimi Watanabe · Takehiro Hotta · Hisashi Sato Received: 1 April 2010 / Accepted: 26 May 2010 / Published online: 16 July 2010 © Springer-Verlag 2010 Abstract In our previous paper, it was found that cot- ton yarn/TiO 2 -dispersed resin photonic crystals were fab- ricated successfully by applying textile technology. How- ever, it is difficult to apply for practical use because these photonic crystals cannot change their shape flexibly. In this study, we fabricate the flexible photonic crystals using high- dielectric constant fibers. The high-dielectric constant fibers were made by inserting alumina balls into Teflon tubes. The crossed linear-fiber laminated fabric and multilayered wo- ven fabric with an fcc lattice structure were structured by aligning high-dielectric constant fibers periodically. These photonic crystals consist of air and high-dielectric constant fibers. The attenuation of transmission amplitude through the photonic crystals was measured. The photonic crystal of crossed linear-fiber laminated fabric exhibits a forbidden gap in the range from 16 to 18 GHz range. On the other hand, the photonic crystal of multilayered woven fabric, which was fabricated by the same parameter with crossed linear-fiber laminated fabric, also exhibits a forbidden gap in the range from 13 to 16 GHz range. Thus, we can suc- cessfully fabricate flexible photonic crystals of woven fabric using high-dielectric constant fibers. 1 Introduction In recent years, the fabrication and physical characterization of photonic crystals have gained increasing interest due to Y. Watanabe ( ) · T. Hotta · H. Sato Department of Engineering Physics, Electronics and Mechanics, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555, Japan e-mail: yoshimi@nitech.ac.jp Fax: +81-52-7355624 their extraordinary optical properties [1–4]. Photonic crys- tals exhibit a frequency gap or several gaps in spectrum of propagating electromagnetic waves, and then an electromag- netic wave with its frequency from the gap cannot propagate in the structure in any direction. Since the photonic crys- tal has potential applications, such as new wave guides, fil- ters, high-efficiency single-mode light-emitting diode, and so on, various fabrication methods such as lithography and a “top-down” approach have been proposed [5–7]. How- ever, these approaches are relatively expensive and time- consuming processes. From the point of view of technological applications of photonic crystals, the photonic crystal fibers are good can- didates [8–10]. Photonic crystal fibers can be constructed using a long thread of silica glass with a periodic array of air-holes running down its length. If the central hole is absent, a high-index “defect” is generated in the repeating structure, which acts like the core of an optical fiber. Light, which is expelled from the periodic structure surrounding the core, can only propagate along it. It has been demon- strated that the photonic crystal fibers have very unusual properties compared with the conventional fibers [8–10]. Meanwhile, it is easy to fabricate 3-D periodic structures using textile technology. In our previous study, therefore, cotton-yarn/TiO 2 -dispersed resin photonic crystals with dif- ferent dielectric constants were fabricated, and the mi- crowave attenuations of the transmission amplitude through these photonic crystals were measured [11]. Unfortunately, since the cotton-yarn/TiO 2 -dispersed resin photonic crystals are rigid and cannot change their shape flexibly, application of these photonic crystals for practical use is still difficult. The main goal of our study has been to fabricate the flexible photonic crystals by using high-dielectric-constant fibrous material. For this purpose, the high-dielectric-constant fi- brous material was made by inserting alumina balls into