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This study demonstrated our successful visualization of the non-volatile analog resistance changes in a metal/oxide/metal sandwiched structure. The resistance change has been intensively studied and practically utilized in the IoT devices, such as resistive random access memory and resistive analog neuromorphic device. Real-time observation technique of device operation (operando observation technique) by laser-excited photoemission electron microscopy (Laser-PEEM) enabled the visualization. The operando observation showed that the signal intensity of Laser-PEEM changed over the whole of the device area with the analog resistance changes. It is sufficiently certain that the change in signal is due to the creation and repair of oxygen vacancies throughout the device area, because the signal intensity reflects the number of electrons near the Fermi level. Considering the results of this study, we conclude that the analog resistance change depends on the device structure and oxygen vacancy concentration in metal/oxide junctions, which are controllable determinants of the device operation. [ABSTRACT FROM AUTHOR]

Tunable terahertz (THz)-wave generation in GaP crystal was theoretically and experimentally investigated using collinear difference frequency mixing. The wavelength range and length of GaP crystal for efficient difference frequency generation (DFG) were determined by calculating the phase-matching conditions. THz waves from 0.5 to 4.5 THz were generated by collinear phase-matched DFG using a dual-wavelength optical parametric oscillator with two KTiOPO4 crystals in the range of 930–1000 nm. A maximum THz output energy of 5.3 nJ/pulse (peak power of 0.66 W) at 1.9 THz was obtained when the pump energy was 1.2 mJ/pulse. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Terahertz (THz)-wave generation using difference-frequency mixing in an organic 4-N, N-dimethylamino-4′-N′-methyl-stilbazolium tosylate (DAST) crystal was investigated theoretically and experimentally. We developed a dual-wavelength optical parametric oscillator (OPO) with two KTiOPO4 crystals as the input light source. This oscillator has a tunable range from 1300–1450 nm and is pumped by a diode-pumped, frequency-doubled, Q-switched Nd:YAG laser with a pulse duration of 10 ns. Widely tunable THz waves ranging from 2 to 20 THz were generated from DAST crystals with 0.5- and 1-mm thickness using the OPO. THz output energies of 82 nJ (peak power of 10.3 W) at 11.6 THz and 110 nJ (peak power of 13.8 W) at 19 THz were obtained with a 1-mm-thick DAST crystal. Using a tunable THz-wave system consisting of the THz source and a pyroelectric detector, THz spectroscopic data for a polytetrafluoroethylene sheet were obtained and were comparable to data obtained from a conventional far-infrared spectrometer. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Studies characteristics of pyrophosphoric acid proton-exchanged waveguides in waveguides. Method of the study; Results and discussion; Conclusion.

We demonstrate the vortex-chirality control in mesoscopic disk magnets using photoelectron emission microscopy (PEEM). Micrometer-sized vortex-chirality-control devices of permalloy were designed and fabricated by electron-beam lithography and lift-off. The magnetic images were obtained by PEEM using the x-ray magnetic circular dichroism (XMCD) with circularly polarized synchrotron radiation. The XMCD-PEEM observation reveals that the vortex chirality in the designed devices was perfectly controlled by an external applied magnetic field. [ABSTRACT FROM AUTHOR]