21COE プログラム「機械システム・イノベーション」平成17年度第4回公開セミナーを開催いたします。ご参加いただきますようどうぞ宜しくお願い申し上げます。
| 講師 |
Associate Professor Zhuomin Zhang, Ph.D.
(George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology) |
| 題目 |
Coherent Thermal Emission in Modified One-Dimensional Photonic Crystals |
| 日時 |
2005年7月8日(金) 16:00〜17:30 |
| 場所 |
工学部2号館・28号講義室 |
| 講演要旨 |
Spectral and directional control of thermal emission is important for applications in optoelectronics and energy conversion. A number of structures have been proposed as coherent emission sources, which create spectral emission peaks in well-defined directions. The grating structure was commonly used, and coherent emission in gratings was achieved by excitation of surface polaritons or surface waves. The present study demonstrates that coherent emission can be realized based on a multilayer structure, consisting of a semi-infinite one-dimensional photonic crystal coated with a polar material (such as SiC). We have identified three modes that can enhance the thermal emission in a narrow mid-infrared wavelength band. (1) By excitation of surface waves at the interface between SiC and the photonic crystal, coherent emission can be achieved for both the s polarization (TE wave) and p polarization (TM wave). The resulting emission peak is confined in a narrow angular range (high directional). (2) Thermal emission from the proposed structure can also be significantly enhanced by the cavity resonance mode, similar to that of a Fabry-Perot etalon. The resulting coherent emission peaks have a broad angular distribution (different-type emitter). (3) For p polarization, the Brewster mode (at which the reflectivity between air and SiC is minimal) can also induce large emissivity peaks in the stop band of the photonic crystal. The proposed planar structure involves dielectric films only without gratings and can be used to realize coherent emission for either polarization. |
| 参加者 |
RA 10名、PD 3名、教官 5名 |
| 主な議論 |
マイクロスケール加工のグレーティングに加えて薄膜多層構造の材料を用いた
材料などからの特異な射出率（波長依存性、角度依存性）などと近接場光などの理論的な
研究結果について議論された。近接場放射を用いたシステムが本当に
エネルギーデバイスとして利用可能なのか、実験的な確証が得られているのか、
射出率は１を超えられるのかなどの議論があった。
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