The authors have studied the transport properties of carbon nanotube quantum dots under terahertz (THz) wave irradiation. The experimental data have shown that the satellite currents are generated with the THz irradiation, and that the peak position of the satellite currents varies linearly with the THz photon energy. These results provide experimental evidence for photon-assisted tunneling in the THz region. The present observation provides the interesting possibility of developing a highly sensitive and frequency-tunable THz detector capable of high-temperature operation.
We report on a highly sensitive terahertz (THz) detector based on a carbon nanotube (CNT) transistor, which is integrated with a two-dimensional electron gas (2DEG) in a GaAs/AlGaAs heterostructure. The operation principle of this device is that the CNT transistor senses electrical polarization induced by terahertz-excited electron-hole pairs in the 2DEG. The magnetic field dependence of the terahertz response signal (CNT current) is shown to follow features of cyclotron resonance of the 2DEG, indicating the validity of the above mechanism. The utilization of the present device structure and mechanism has enabled the detection of a small number of terahertz photons.
In recent years the electronic endoscope has been increasingly used by medical practitioners in Japan. However, it has been noted that the problem of too strong light refection, which, not only hampers the procedure but also causes eye exhaustion, at the same time making photographic or computerized image processing difficult, is more frequently experienced and is more serious in magnitude when compared with using a conventional fiberoptic endoscope (catch‐light phenomenon). In order to ameliorate this problem the authors experimented with the use of circularly polarized light. The combined use of a circular polarizing device to the efferent light path and a filter which blocks certain types of Circularly polarized light to the afferent path has proved to be very effective in eliminating the incidence of catch‐light troubles, thus making the endoscopic procedure smooth and efficient.
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