Tomographic implementation of astronomical speckle imaging from bispectra

A bispectral method for astronomical speckle imaging utilizes an average speckle bispectrum of an object to derive its Fourier phase. There has been, however, a problem in conventional bispectral algorithm owing to difficulty in processing bispectral data in a four-dimensional (4D) space. In this paper, we propose an implementation to overcome this problem, where a one-dimensional (1D) object projection is reconstructed from a two-dimensional (2D) average bispectrum of speckle projections, and object projections so obtained at various angles are then tomographically combined into a 2D object image. In this tomographic approach, processes are separable into those for individual projection angles, implying that bispectral data required to be stored at a time are from 4D to 2D and computation time can be substantially reduced by parallelizing angle-by-angle processes. We have performed experiments using simulated and observed data, and have demonstrated the feasibility of the present approach with an achievable accuracy comparable to that of a conventional approach.     

Charge density study under high pressure

The experimental and analytical method of the high-pressure powder experiment at BL10XU, SPring-8, is described. There is no doubt that BL10XU must be one of the most appropriate beam lines for high pressure X-ray diffraction experiment taking advantage of third generation synchrotron source. As an example of the advanced charge density study under high pressure, the structural change of Cs₂Au₂Br₆ by applying pressure is studied by Rietveld/MEM analysis. It reveals that the structural change of Cs₂Au₂Br₆ by applying pressure occurs basically at electron level, such as valence state change and chemical bonding, which may be called the electronic phase transition.     

Light-controlled microstrip line coupler

Conclusions We have analyzed coupling properties of the coupled microstrip lines whose substrate contain electron-hole plasma by means of the spectral domain method. Scattering parameters in each ports have been evaluated numerically as a function of plasma density.Experiments were carried out using high resistivity silicon and LEDs. The agreement of the theoretical and experimental results was satisfactory. The plasma density observed in the experiments is one-third as large as the theoretically estimated value.     

Ti-sapphire femtosecond pulse pumped laser emission from all-plastic organic waveguide with distributed feedback resonator

We demonstrated the spectrally narrowed laser emission from all-plastic organic waveguide with the distributed feedback (DFB) resonator pumped by Ti-sapphire femtosecond laser. We fabricated the DFB resonator on a surface of a photoresist polymer using an interference of laser beams. All-plastic waveguide with organic dyes dispersed in poly(N-vinylcarbazole) and polystyrene matrix was spin-coated on a DFB resonator. Very narrow full width at half maximum (FWHM) of 0.15 nm in emission wavelength was observed, whereas an excitation laser of Ti-sapphire femtosecond laser has broad FWHM of 14 nm.     

Effects of high-concentration phosphorus doping on crystal quality and lattice strain in SiGe HBTs

A high-concentration in-situ phosphorus-doping technique for silicon low-temperature epitaxial growth with Si₂H₆ has been developed. Growth temperature has an impact on the crystal quality and on lattice strain of phosphorus-doped silicon layers. Resistivity, micro-Raman spectroscopy, and high-resolution X-ray diffraction indicated that good crystal quality was achieved at a growth temperature of 525 °C. On the other hand, growth pressure has little influence on crystal quality or on lattice strain except for surface morphology. By optimizing epitaxial growth conditions, an extremely high concentration of phosphorous doping was achieved without a high-temperature activation annealing, and the resultant good crystal quality of the phosphorus-doped silicon layer gave a very low resistivity. Accordingly, the high-concentration in-situ phosphorus doping is a powerful technique to fabricate future ultra-high-speed SiGe HBTs.     

Evaluation of immobilized-lysozyme by means of TOF-SIMS

Evaluation of immobilized-proteins on bio-devices is important for the development of sophisticated devices. Lysozyme molecules immobilized on substrates were evaluated by means of time-of-flight secondary ion mass spectrometry (TOF-SIMS). Two types of the lysozyme-immobilized samples were prepared by controlling the binding parts, i.e., the amino groups or carboxyl groups, of the protein. The TOF-SIMS spectra of each sample were analyzed with mutual information to select fragment ions specific to each sample. According to the results, differences between the samples being immobilized in the different ways are suggested, and the surface structure of the lysozyme molecule immobilized at amino groups is determined based on three-dimensional structure of lysozyme in the Protein Data Bank.     

Complex-number asymmetry parameters of the optical Fano effect in ring resonators

We studied the sharp asymmetric Fano line shape in fiber ring resonator systems and provided an explicit expression for asymmetry parameters using the physical parameters of the system. The fiber ring system was controllable and reconfigurable, allowing us to produce a variety of Fano line shapes in different configurations. Experimentally observed asymmetric spectral structures were fully reproduced using the complex-number asymmetry parameters, validating the approximations used to reduce the analytical expression for the line shape to the phenomenological Fano formula. The results may be useful in the design of on-chip application systems.     

Two-photon-induced laser annealing for enhancement of photoluminescence intensity in ZnSe crystal

We present the finding that photoluminescence intensity in ZnSe crystal is enhanced after exposure to a femtosecond laser beam. After the crystal was illuminated with laser light of 1.04 MW/cm(2) during 300 s, photoluminescence intensity was increased approximately 20%. The region in which photoluminescence intensity was enhanced was localized in the optical axis, because this phenomenon occurred in the two-photon excitation process. It is possible to achieve three-dimensional control of photoluminescence intensity by illumination with laser light.     

Ultra-narrow interval angular control signal for holographic data storage system

Optical Review - A precise and fast method for controlling the reference-beam angle of an angular-multiplexed holographic data storage system (HDSS)—to achieve larger capacity and faster...     

Time variation of the electromagnetic transfer function of the earth estimated by using wavelet transform

In order to accurately estimate the geomagnetic transfer functions in the area of the volcano Mt. Iwate (IWT), we applied the interstation transfer function (ISTF) method to the three-component geomagnetic field data observed at Mt. Iwate station (IWT), using the Kakioka Magnetic Observatory, JMA (KAK) as remote reference station. Instead of the conventional Fourier transform, in which temporary transient noises badly degrade the accuracy of long term properties, continuous wavelet transform has been used. The accuracy of the results was as high as that of robust estimations of transfer functions obtained by the Fourier transform method. This would provide us with possibilities for routinely monitoring the transfer functions, without sophisticated statistical procedures, to detect changes in the underground electrical conductivity structure.