High magnification microscopic system focusing on transparent liquid/liquid interface formed in thin-layer two-phase microcell.

A thin-layer two-phase microcell was fabricated without an adhesive, which showed no fluorescence and resisted acids. The lower hollow of the microcell was thin (0.18 mm), which was in the range of the working distance of the used objective of high magnification (60x) and high numerical aperture (1.2). A reflection method using probe light was newly employed for focusing the objective on a transparent dodecane/water interface strictly with an inverted microscope. The system was applied to in situ fluorescence microscopic measurements of the dynamics of single DNA molecules (165600 base pairs) at the dodecane/water interface.     

Development of a “Built-in” Scanning Near Field Microscope Head for an Atomic Force Microscope System and Stress Mapping of an Al2O3/ZrO2 Eutectic Composite

We constructed a scanning near-field optical microscope (SNOM) on a commercially available atomic force microscopy (AFM) apparatus (SPM-9500J2; Shimadzu Corp.) to measure the stress distribution in ceramic composite materials. Features of our SNOM system are: (1) a compact SNOM head substituted for the original AFM head; (2) a wide scanning range (125 × 125 μm²) inherited from the original scanner; (3) use of conventional shear-force regulation; (4) an optical system for the illumination-collection (I-C) mode; (5) excitation by a 488 nm line of an Ar-ion laser, and (6) light detection by photon counting or a polychromator equipped with an electronically cooled charge coupled device (CCD). This SNOM system was used to measure the surface structure and stress distribution of an Al₂O₃/ZrO₂ eutectic composite. We simultaneously measured topographic images and fluorescence spectra of an Al₂O₃/ZrO₂ eutectic composite. We estimated its peak intensity, peak position, and peak width from the fluorescence spectrum during scanning, which respectively correspond to the abundance of Al₂O₃, stress in the grain, and the anisotropy of that stress. Mapping images showed that the stress and its anisotropy were weaker in the center of the Al₂O₃ grain than its boundary between Al₂O₃ and ZrO₂. That observation suggests that Al₂O₃ underwent intense anisotropic stress induced by volume expansion in the phase transition of ZrO₂ from the cubic phase to the monoclinic phase during preparation.     

THE DESIGNS OF HIGH EFFICIENCY LAUNCHER OF QUASI-OPTICAL MODE CONVERTER FOR HIGH POWER GYROTRONS

A high efficiency launcher of quasi-optical (QO) mode converters for high power gyrotrons have been designed and tested. A helical cut launcher radiates the RF power via its straight cut onto the first phase correcting mirror. The launchers have been optimized for the TE_31.8 mode at 170 GHz and TE_22.6 mode at 110 GHz by numerically optimizing a launcher surface. The helical cut of the launcher has been optimized by taking the taper angle into account. Further more, the amplitude of the surface perturbation have been optimized for improved focusing in order to reduce the diffraction losses at the helical cut. Low power measurement shows a good agreement with the design. High efficiency characteristics of the design have also been calculated on the assumption of frequency downshift due to the thermal expansion of the cavity and stepwise frequency tuning by changing the operating mode. Besides, the possibility of high efficiency launcher for higher mode is discussed, and these results give the prospect to high efficiency long pulse gyrotrons.     

Introduction of several trifluoromethyl groups onto the activated aromatic materials with CF3TMS-CuI-KF system

Trifluoromethylation onto the tetrafluorophthalonitrile and tetrafluoroisophthalonitrile has been carried out using CF₃TMS-CuI-KF system, and it was demonstrated that these trifluoromethylation enabled us to successfully construct di- and/or tri-trifluoromethylated benzonitriles via the decyanotrifluoromethylation.     

Measurement on Spot Size Dependence of Dense WDM Dielectric Multilayer Filters

We present the spot size dependence of dielectric multilayer filters for use in dense WDM systems. We found large dependences of filter performances on the spot size and the incident angle of input light, which should be important for miniaturizing multi-channel add/drop filters.     

Formulation for XPS spectral change of oxides by ion bombardment as a function of sputtering time

XPS measurement revealed that the original state of TiO₂ was changed to Ti₂O₃ and TiO by ion bombardment. TiO₂ decreased and Ti₂O₃ increased at the initial stage. TiO increased at a later stage than Ti₂O₃. Each of them saturated after enough sputtering time.A formulation was proposed in order to explain the change of XPS spectra for oxides as a function of ion sputtering time. This formulation was based on reaction equations that contain two reduction processes (from TiO₂ to Ti₂O₃ and from Ti₂O₃ to TiO), and sputtering effects. Using four fitting parameters (two reduction coefficients, sputtering yield and information depth), the present formula was fitted to the experimental results. The fitting results agree satisfactorily with the experimental results. The calculation shows that the reduction coefficient from TiO₂ to Ti₂O₃ is about ten times larger than that from Ti₂O₃ to TiO. This calculation predicts that surface composition of an oxide that is changed by ion bombardment will reach a different value depending on its bulk composition. Moreover, the present formulation can determine the chemical states of compounds changed by ion bombardment.     

Numerical reconstruction of an infrared wavefront utilizing an optical phase modulation device

We utilize nitroanisole, that absorbs infrared (IR) radiation as heat, as an optical modulation device based on a thermal process. The nitroanisole exhibits a thermal lens effect, i.e. a temperature dependent refractive index. Hence, the nitroanisole can induce phase modulation to visible light, in direct response to intensity of the incident IR radiation. The proposed method can be used to obtain the phase modulation distribution that corresponds to the IR intensity distribution, i.e. the IR hologram itself, on the nitroanisole by examining the phase map of visible light that is modulated upon passing through the nitroanisole. The IR wavefront can be reconstructed by calculating extracted IR holograms through the Fresnel transform. It is verified that both the amplitude and the phase of the IR wavefront can be reconstructed accurately by proposed method.     

Slow cyclotron instability in a high-power backward-wave oscillator

The linear dispersion relation of a backward-wave oscillator (BWO), derived earlier by the authors, is modified to include effects of RF surface current at the beam-vacuum interface. This modified dispersion relation results in an unstable interaction between the slow cyclotron mode (SCM) and the structure mode in addition to the conventional Cherenkov instability caused by the slow space charge mode. Numerical analysis is then carried out using parameters of a BWO experiment at University of Maryland. Fine structure of the SCM instability is elucidated. The analysis indicates that BWO radiation would not be suppressed near cyclotron absorption in an infinitely long system.