2002 Fiscal Year Final Research Report Summary
Generation of electrical signals in THz band from coherent charge dipoles in microcavities
| Project/Area Number |
12305006
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Applied optics/Quantum optical engineering
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| Research Institution | HIROSHIMA UNIVERSITY |
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Principal Investigator |
YAMANISHI Masamichi Hiroshima University, Graduate School of Advanced Sciences of Matter, Professor, 大学院・先端物質科学研究科, 教授 (30081441)
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| Co-Investigator(Kenkyū-buntansha) |
KITAGAWA Jiro Hiroshima University, Graduate School of Advanced Sciences of Matter, Research Associate, 大学院・先端物質科学研究科, 助手 (90346528)
KADOYA Yutaka Hiroshima University, Graduate School of Advanced Sciences of Matter, Associate Professor, 大学院・先端物質科学研究科, 助教授 (90263730)
GONOKAMI Makoto University of Tokyo, Graduate School of Engineering, Professor, 大学院・工学研究科, 教授 (70161809)
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| Project Period (FY) |
2000 – 2002
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| Keywords | Semiconductor quantum wells / Quantum confined Stark effect / Sub-picosecond electrical signals / THz electromagnetic waves / Cavity polariton / Exciton |
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| Research Abstract |
In this project, we aimed at the generation of THz-electrical signals from coherent charge dipoles in semiconductor quantum wells (QWs) by exciting them with sub-picosecond laser pulses, and also at applying THz electrical signals to the semiconductor microcavities, where polariton mode oscillation is excited. For this purpose, after preparatory experiments for the building a measurement setup using co-planer microstrip lines, we designed a microstrip line structure, where dc and THz electric fields can be applied perpendicularly to the QW plane. From the numerical analysis based on finite difference time domain (FDTD) method, we found that an in-line gap structure can be used for this purpose. Using the fabricated such kind of devices, we successfully observed THz electrical signals, whose rise-time is about 400 fs, using a QW as a detector. Then, we searched the conducting line materials, which allow us a optical access through the line. We decided to use ITO films as a candidate of such a material. After the establishment of fabrication process, we successfully formed a microstrip line device based on ITO. Although the properties are not satisfactory, we could observe an electrical signal perpendicularly applied to the QW plane. During the investigation, we found that even with a single microstrip line, THz signals can be guided if the propagation distance is not too long. Such a guiding mode may be useful in some kind of applications. We also investigated the polariton mode oscillation in semiconductor microcavities under static electric field, and found that the phase of the oscillations vary with the change of the electric field and that the phase change suggests strongly that the variation of exciton-exciton interactions, which is a key factor in excitonic nonlinearity. To the best of our knowledge, this is the first observation of the alteration of exciton-exciton interactions.
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