Akira Kawakami

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We present the first experimental results on waveguide-type all-NbN SIS receivers fabricated on MgO substrates designed in a frequency range from 780 to 960 GHz. The receiver has a resonant distributed SIS junction one wavelength long at 870 GHz as the tuning circuit and a diagonal feed horn. The mixer chip was fabricated with accuracies of less than 10 im(More)
Antimony(III) was preconcentrated on activated carbon (AC) as the antimony(III)-pyrogallol complex. Prior to the preconcentration, antimony(V) was reduced to antimony(III) with potassium iodide and ascorbic acid. The antimony adsorbed on the AC was determined by graphite furnace atomic absorption spectrometry as an AC suspension. The method was applied to(More)
SUMMARY We report on progress in the development of high current density NbN/AlN/NbN tunnel junctions for application as submillimeter wave SIS mixers. A ultra-high current density up to 120 kA/cm 2 , roughly two orders of magnitude larger than any reported results for all-NbN tunnel junctions, was achieved in the junctions. The magnetic field dependence(More)
The properties of the coherence-or-power selectable operation of an external-cavity semiconductor diode laser through the control of intracavity polarization states have been characterized in detail. In our technique, a diffraction grating and a reflector functioned as a polarization-dependent output coupler, such that the portion of light fed back to the(More)
— We are developing a low noise heterodyne receiver at 3THz band for applications of atmospheric and astronomical research and for application of wireless communications. We have developed a phase-locking system of a terahertz quantum cascade laser (THz-QCL) by using a hot electron bolometer mixer. The THz-QCL was locked to terahertz reference generated by(More)
The survey of 222Rn concentration in the air of tunnels constructed during World War II has been performed using a solid-state nuclear track detector technique. For the practical application of this technique to the determination of 222Rn concentrations in air, some basic properties were experimentally examined on the cellulose nitrate film, Kodak LR 115(More)
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