Transmission Characterization of Drilled Alternating-Layer Three-Dimensional Photonic Crystals
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Transmission Characterization of Drilled Alternating-Layer Three-Dimensional Photonic Crystals Eiichi Kuramochi1, Masaya Notomi1, Itaru Yokohama1, Jun-ichi Takahashi2, Chiharu Takahashi2,3, Takayuki Kawashima4, and Shojiro Kawakami4 1 NTT Basic Research Laboratories, NTT Corporation, 3-1 Morinosato Wakamiya, Atsugi-shi, 243-0198 Japan. 2 NTT Telecommunications Energy Laboratories, NTT Corporation, 3-1 Morinosato Wakamiya, Atsugi-shi, 243-0198, Japan. 3 NTT Advanced Technology Corporation, 3-1 Morinosato Wakamiya, Atsugi-shi, 243-0198, Japan. 4 NICHe, Tohoku University, Aramaki Aza Aoba 04, Aoba-ku, Sendai, 980-8579 Japan. ABSTRACT We propose a new three-dimensional photonic crystal structure or drilled alternating-layer photonic crystal (DALPC), which can be fabricated by a combination of the deposition of alternating layers of dielectric films and one-time dry etching. Our band calculation predicts that the DALPC has a photonic band gap (PBG) in all directions. We fabricated a Si/SiO2 DALPC by electron beam lithography, bias sputtering, and fluoride-gas electron cyclotron resonance etching. We measured the light transmission of the DALPC sample in both the in-plane and vertical directions. We observed a transmission minimum around the 1.4-µm-wavelength for all measured directions and TE/TM polarizations, which demonstrated a potential of the DALPC as a three-dimensional PBG material. INTRODUCTION Photonic crystals (PC) [1] are now the subject of considerable attention. To pursue a full PBG or a very high Q-value, the PC structure should be three-dimensional (3D). It is relatively easy to construct the self-assembly-based 3D PCs [2,3], but it is very difficult to introduce structural modulations such as a defect to realize device functions. By contrast, device functions can be readily introduced into a lithography-based 3D structure, in which all the PC elements are defined artificially. However, the lithography-based 3D structures reported to date [4-7] require a very complicated fabrication process that needs a large number of alignment processes or sophisticated micromachining, thus making it unrealistic for use in producing commercially viable PCs. We have proposed a novel three-dimensional photonic crystal, or drilled alternating-layer photonic crystal (DALPC), which can have a full PBG [8,9]. Our DALPC is based on a two-dimensional alternating layer structure and can be deposited by rf-bias sputtering. The automatic shaping effect that occurs in bias sputtering (autocloning) was discovered and developed by Kawakami and co-workers to fabricate 3D PCs [10,11]. We added a nanolithography to the autocloning-based alternating-layer structure to realize a full PBG by creating connectivity in the vertical direction. The main DALPC fabrication processes, namely two-time fine-line lithography, one sequential sputtering deposition, and one-time drilling by dry etching, are based on very mature technologies with few process steps. So the DALPC structure should be highly controllable and easy to fabricate. In this paper w
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