成果報告書詳細
管理番号20110000001137
タイトル*平成22年度中間年報 ナノテク・先端部材実用化研究開発/ナノホール/ダイポール・アンテナを用いた赤外線放射および受信素子の研究開発
公開日2011/9/9
報告書年度2010 - 2010
委託先名独立行政法人物質・材料研究機構 国立大学法人大阪大学 豊田合成株式会社 株式会社豊田中央研究所
プロジェクト番号P05023
部署名電子・材料・ナノテクノロジー部
和文要約和文要約等以下本編抜粋:1. 研究開発の内容及び成果等 (1)屈折率制御型ナノホール・アンテナを用いた赤外線走査素子の開発 1) ナノホール配列積層構造の設計(主担当:豊田中央研究所) 赤外領域における電磁波問題を取り扱う構造最適化の確立と広角度にビーム走査可能なナノホール配列積層構造の設計を行った。20nmのAlと80nmのSiO2との5周期の多層構造に直径500nmのホールを1μm間隔で10個並べ、隣り合うナノホール形状を○から□まで角部のRを緩やかに変化させる設計で、1.5μmの赤外線ビームの等位相面を傾斜させ、ビームを偏向させることができることを見出した。
英文要約An infrared beam steering device is designed with a planer prism of grade negative index material (NIM). The planer prism is realized by tailoring effective refractive index of NIM with spatial dispersion in a stacked hole array, gradually changing metamaterial structure in it. The hole array in 5-period 20nm-Al / 80nm-SiO2 multilayer is composed by square holes whose side is 500 nm arranged on 1 μm lattice. The curvatures of corners of the square holes, R, are controlled. In the dispersion curves of square and circle holes in consideration of the Al metal dispersion, a radiated angle of the output beam is changed from 0 to 2 degrees with changing wavelength of laser from 1470 nm to 1540 nm.
The designed hole array was fabricated by electron beam lithography and reactive ion etching. The shapes of nano-holes were made by the processing accuracy of 10% compared with the designed value, and near-vertical holes were obtained in the low chamber pressure. From the measurement results of the electromagnetic wave propagation at the corresponding frequencies, beam steering of 1 degree in this planer prism structure was clearly shown. The value of beam steering angle is good agreement with the simulated one.
For practical application, output beam angle is changed by changing the refractive index of the liquid crystal infiltrated in the air-hole by applying the external electric field. The liquid crystal was infiltrated into nano-holes and the orientation direction of the liquid crystal was observed by two-photon fluorescence microscopy. The experimental validation of active beam steering with liquid crystal is currently being planned with new designed hole array of large steering angle.
In order to obtain the more sensitive infrared-receiving device, a coplanar-strip-type transmission line was coupled with the antenna of the device. The transmission line was designed so as to suppress the electro micro wave emission during the transmission of the 30 THz-pulsating signal via the line, and to be applied to arrayed antenna. The antennas and the rectifiers (metal-insulator-metal tunneling diodes (MIM diodes)) of the newly designed infrared-receiving devices were fabricated mainly using the electron-beam lithography and lift-off techniques.
The MIM diodes of the fabricated devices showed a clear rectification property. When a CO2 laser beam (wavelength: 10.6 micron) was irradiated onto the infrared-receiving device, 30 pA of the output current was observed although the signal to noise (S/N) ratio was very low. From the observed value of the output current, the infrared sensitivity of the device is calculated to be 0.01 A/W, which is 1/10 of the target value of the sensitivity. We are planning reconsideration of the substrate material, formation of the higher-purity tunneling barrier of the MIM diode, improvement the fabrication process and noise reduction to attain the target sensitivity at 0.1 A/W.
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