| Budget Amount *help |
¥3,700,000 (Direct Cost: ¥3,700,000)
Fiscal Year 2004: ¥1,800,000 (Direct Cost: ¥1,800,000)
Fiscal Year 2003: ¥1,900,000 (Direct Cost: ¥1,900,000)
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| Research Abstract |
The major aim of this project was the control of propagation velocity of sub-picosecond electrical signals on micro strip lines (MSLs) involving semiconductor quantum wells, where electrons and holes are generated by with, for example, optical excitation. Along with the fabrication of the devices and the measurements, three-dimensional calculations of the electromagnetic fields were performed by using finite-difference-time-domain (FDTD) software. The major results are as follows.
(1)It was found that the electrical signals observed, at the beginning of this project, in the MSLs made on semiconductor substrates are those waveguided only by the single signal line formed on the substrate surface. The waveguiding by single metallic lines has been reported in microwave and optical regimes. The strip lines in THz-frequency regime, where the real and imaginary parts of the complex conductivity of metals have the values in the same level, can be a good system for the investigation on the influ
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ence of surface plasmons on the electromagnetic waveguides. We also found that the attenuation and the dispersion of the signals along the single metallic line can be even lower than the conventional MSLs, if the line is covered by a uniform dielectric films. Hence we can expect the application of single-line waveguides in the future.
(2)We successfully fabricated the MSLs where the ground plane is made of an optically-transparent conductor, ITO. In such MSLs, optical access into the region between the signal line and the ground plane is possible. It was confirmed, experimentally, that the signals whose spectral range is below 1 THz can be transmitted for more than 1 mm with good propagation characteristics. We also showed that the use of Drude model for ITO is necessary for the precise prediction of the propagation characteristics in the frequency higher than 1 THz, on the basis of the FDTD calculation.
(3)It was experimentally verified that the transmission of sub-picosecond electrical signals over a few mm is possible in the thin film MSLs in which the polymer dielectric is used.
(4)Methods for embedding semiconductor quantum wells in the MSL described above were established. In the measurement, the control of the propagation velocity was not observed, mostly because of the insufficient excitation of electrons and holes. However, since the device fabrication method established in this work has a good versatility, we can expect the progress for realizing functional MSLs in future. Less
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