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In this paper, we propose and demonstrate a new method for measuring the trap frequency from the fluorescence dynamics of an ion, initiated using fast trap-center displacement. Here, we observe the coherently excited motion of an ion in a harmonic trap using time-resolved fluorescence detection. Furthermore, Fourier analysis of the ion fluorescence signal was used to determine the trap frequency of an ion with high precision and reproducibility. The results show that our proposed method can be an alternative way to determine trap frequencies in an ion trap experiment. [ABSTRACT FROM AUTHOR]

The fictive temperature (T(sub f) ) and fluorine concentration dependence of structure fluctuation in SiO2 glass were investigated by small-angle x-ray scattering measurement, in this study. It was found that density fluctuation solely contributes to the T(sub f) dependence of structure fluctuation.

A new study investigates dielectric relaxation in silica glass from 20 Hz to 1 MHz and in the temperature range 30-100 deg C.

An investigation of the effects of argon-fluoride-(ArF) excimer laser preirradiation and thermal annealing on the creation of photoinduced defects on synthetic silica glass has been conducted. The experiment confirmed the procedure's enhancing effect on the durability of silica glass treated by conventional ArF-excimer laser. Optical absorption measurements indicate a strong role for preirradiation in the relaxation of weak portions in the glass such as the Si-O-Si bonds.

Light-scattering measurements were used to investigate the glass transition in silica glass. OH ions were found to reduce the activation energy of viscoelastic relaxation and new relaxation was generated due to the local structure change. Such a relaxational process due to impurities could be effective in controlling the performances of silica glass.

The electron-paramagnetic-resonance method is used to study the fictive temperature (T(sub f)) and fluorine (F)-doping concentration dependences of self-trapped holes (STHs) in silica glasses created by UV irradiation at low temperatures. The results reveal that the change in both T(sub f) and F doping can modify the network of SiO2 glass, leading to the suppression of the formation of STHs.

We demonstrate ns-pulsed pumping of terahertz (THz) parametric oscillations in a quasi-triply resonant cavity in a THz waveguide. The THz waves, down converted through parametric interactions between the pump and signal waves at telecom frequencies, are confined to a GaP single mode ridge waveguide. By combining the THz waveguide with a quasi-triply resonant cavity, the nonlinear interactions can be enhanced. A low threshold pump intensity for parametric oscillations can be achieved in the cavity waveguide. The THz output power can be maximized by optimizing the quality factors of the cavity so that an optical to THz photon conversion efficiency, ηp, of 0.35, which is near the quantum-limit level, can be attained. The proposed THz optical parametric oscillator can be utilized as an efficient and monochromatic THz source. [ABSTRACT FROM AUTHOR]

Selenization of Fe films using molecular beam epitaxy equipment was undertaken to prepare FexSey films on GaAs(001) substrates. Their structural and magnetic properties were studied, and the selenized films obtained comprised polycrystalline grains of 100-170 nm. Magnetic anisotropy was weakened when the selenization ratio of the samples was increased.

Interlayer exchange coupling was investigated in highly Co-enriched (75.6 at. %), i.e., in Co antisite defective Heusler alloy Co-Mn-Si-based epitaxial trilayer structures for a wide range of spacer Cr thicknesses (tCr). The exchange coupling parameters J1 (bilinear coupling) and J2 (90° coupling) were estimated from the comparison of experimental and numerical simulations of M-H loops. The comparable contributions of both the bilinear and 90° couplings were observed in a spacer thickness range, tCr ∼ 0.3 to 4.2 nm. The relative angle of magnetization at remanence between the bottom and top Co-Mn-Si layers was found to vary from 67° to a maximum of 152° as a result of competition between bilinear and 90° couplings. In contrast to the observation of strong 90° coupling without any detectable bilinear type 180° coupling in almost stoichiometric and chemically B2-ordered Co2MnSi-based trilayer structures in a previous study, the results in this study clearly indicated the importance of the effect of chemical ordering on dominating 90° coupling in Heusler alloy-based structures. [ABSTRACT FROM AUTHOR]

Photobleaching of self-trapped holes (STH) in low temperature UV-irradiated silica glass has been investigated by the electron spin resonance method. The bleaching time dependence of the decay of two kinds of STH, STH1, and STH2, could be well fitted by the stretched exponential function, and STH2 has a quicker decay than STH1. On the other hand, the decay becomes significant large when the photon energy increases from 1.5 to 2.0 eV, and then keeps constant with a further increase of photon energy. The distributions of the STH continuums are estimated at the positions on top of the valence band, being 1.66±0.27 eV for STH1 and 1.63±0.33 eV for STH2. A possible recombination mechanism is proposed to explain the decay of STH signals. [ABSTRACT FROM AUTHOR]

The fictive temperature, T[sub f], and fluorine concentration dependences of structure fluctuation in SiO[sub 2] glass was investigated by small-angle x-ray scattering measurement. Regardless of F concentration, density fluctuation in SiO[sub 2] glass is proportional to T[sub f] and depends on structural relaxation. Concentration fluctuation does not depend on T[sub f] and is almost proportional to F concentration. And it implies that F is incorporated into the glass structure at temperatures considerably higher than the T[sub f] on which glass structure freezes. Contributions of the density and concentration fluctuations to the structure fluctuation were estimated. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Studies the fictive temperature dependence of density fluctuation in silicon oxide glass. Use of the small-angle x-ray scattering measurement; Effect of structural relaxation on the density fluctuation; Estimation of the isothermal compressibility.

A frequency-tunable terahertz wave was generated from GaP crystals using an optical parametric oscillator as the pump source and a YAG laser (1.064 µm) as the signal source. By tuning the very small angle, θ[sub in], between the pump and signal light beam directions, tunable terahertz waves over the frequency range from 0.5 to 3 THz were obtained. The THz frequency changed almost linearly with the angle θ[sub in]. The precise noncollinear phase matching condition is discussed. The pulsed peak power of the THz wave was as high as 480 mW at 1.3 THz. [ABSTRACT FROM AUTHOR]

We investigated platinum (Pt)-related defects in silicon (Si) based on the measurement of their optical absorption and found optical absorption peaks related to Pt clusters. Pt and H were separately doped in FZ-Si by heating at 1000-1300 °C followed by quenching in water. Optical absorption spectra were measured at about 5 K with a Fourier transform infrared spectrometer. In a specimen doped with a higher concentration of H than of Pt, we observed optical absorption peaks due to four types of Pt-H complexes. In specimens with a higher concentration of Pt than of H, peaks were observed in the region from 1300 to 1700 cm[sup -1]. Based on the peak shift due to the hydrogen isotope and the dependence on excitation energy and the annealing behavior, these peaks are thought to be due to the electronic transitions of Pt-related defects such as Pt clusters, rather than the local vibrational modes of H. The defect centers which gave rise to optical absorption at about 1301, 1318, 1452, and 1474 cm[sup -1] were IR-active centers under illumination and the optical threshold energy was determined to be about 0.34 eV by applying Lucovsky's model [Solid State Commun. 3, 299 (1965)]. [ABSTRACT FROM AUTHOR]

The effects of fluorine (F) doping on silica glass structure, structural relaxations, and vacuum ultraviolet (VUV) absorption edge were investigated by the infrared and vacuum ultraviolet absorption measurements. Linewidth of 2260 cm[sup -1] absorption band, which is one of the good indicators of structural disorder, decreases proportionally to the fictive temperature (T[sub f]). On the other hand, it is irrespective of F concentration. Structural relaxations are strongly stimulated by F doping. The transparency near the absorption edge depends on both F concentration and T[sub f]. When T[sub f] is constant, absorption edge shifts to a shorter wavelength proportionally to the F concentration. These results strongly suggest that there are two main factors that control the VUV absorption edge of F-doped silica glass; band gap widening by increasing Si–F bond and reduction of structural disorder. The latter factor is not directly caused by structural change by F doping. F enhances the structural relaxation, and it is easy to obtain samples with lower T[sub f], resulting in reducing structural disorder. Furthermore, a way to determine T[sub f] of F-doped silica glass is offered. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We have demonstrated the change of the Raman spectra in F-doped silica glasses with various fictive temperatures, and have also presented a useful peak-deconvolution technique for evaluating the relative concentration of D1 and D2 bands that could be attributed to four- and three-membered ring structures. The intensities of D1 and D2 bands are mainly dominated by the fictive temperature, and they are not almost affected by the F content at the same fictive temperature. It has been made clear that the intensity of D1 band as well as D2 band has a linear relationship with the IR peak position around 2260 cm-1 that is correlated with the average Si–O–Si bond angle, irrespective of the F content. The “activation energies” of D1 and D2, estimated from the Arrhenius plot, are 0.26 and 0.41 eV, respectively. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The space layer thickness dependence of interlayer exchange coupling is examined in the fully epitaxial trilayers of the [Co.sub.2]MnAl (CMA)/Cr/CMA structure. The comparison of the results of the experiments and the simulations of magnetization curves have disclosed novel behavior, dominating the 90[degree] coupling and the absence of 180[degree] coupling.

The magnetization process of epitaxial [Co.sub.2]MnSi/Cr/[Co.sub.2]MnSi trilayers with oscillatory interlayer exchange coupling is investigated. The 90 degree Celsiusoupling energy and the anisotropy constant has disclosed that the strength of 90 degree Celsiusoupling decreases exponentially with the spacer layer thickness.

The electron spin resonance method is used to investigate photobleaching of self-trapped holes (STH) in low temperature ultraviolet (UV)-irradiated silica glass. The decay of both ST[H.sub.1] and ST[H.sub.2] can be described by the stretched exponential function and the recombination of electrons with STHs can account for the decay of STH signals.

The evolution of the photoluminescence maximum and the full width at half maximum (FWHM) of ZnO quantum wells (QW) with temperature by Monte Carlo simulation is studied. It is stated that the density of localized states used in the simulation for the CdZnO QW is consistent with the absorption spectrum.

Structural relaxations in fiber cores and claddings with various fluorine concentrations were investigated. It was found that structural relaxation in the core is strongly affected by that in the cladding and this effect leads to an approach to control structural relaxation in fiber core for reducing the Rayleigh scattering loss in optical fibers.

Fictive temperature dependence of density fluctuation in SiO2 glass is investigated by the small-angle x-ray scattering measurement. The study shows that the density fluctuation in SiO2 glass is less than 3.6%, hence, the density deviation or size of the inhomogeneous structure is small.

Presents information on a study which applied the high-accuracy universal polarimeter method on the incommensurate phase of [N(Ch[sub3])[sub4]][sub2] CuCl[sub4]. Determination of gyration tensor; Determination of the soliton density; Temperature dependence.

Provides information on a computer code developed to simulate the dose dependence of concentration profiles and sputtering yields under ion implantation. Calculation method; Nitrogen implantation into zirconium.

Presents a study which examined the domain switching of ferroelectric triglycine sulfuric acid and Rochelle salt by observing optical gyration along the ferroelectric axes and measuring rotation of the indicatrices around the same axes. Method for distinguishing the twinning mechanism of the ferroelectric domains; Change of gyration and orientation of indicatrix; Observations of the optical phenomena.

Investigates the influence of fast neutron irradiation on critical current and its strain dependence in a bronze processed fine multifilamentary Nb[sub3]Sn superconducting composite. List of the specification of the bronze processed fine multifilamentary Nb[sub3]Sn superconducting composite wire specimen; Summary of material parameters of the multifilamentary Nb[sub3]Sn.

The low-energy spin-wave dispersion in polycrystalline Nd-Fe-B magnets was observed using neutron Brillouin scattering (NBS). Low-energy spin-wave excitations for the lowest acoustic spinwave mode were clearly observed. From the spin-wave dispersion, we were able to determine the spin-wave stiffness constant Dsw (100.0±4.9 meV.Å 2) and the exchange stiffness constant A (6.6 ± 0.3 pJ/m). [ABSTRACT FROM AUTHOR]

The spacer layer thickness dependence of interlayer exchange coupling has been investigated in the fully epitaxial trilayers of the Co2MnAl (CMA)/Cr/CMA structure. A series of high-quality samples of CMA (20 nm)/Cr (tCr=0.3–8.1 nm)/CMA (10 nm) trilayers was prepared on a MgO substrate by ultrahigh vacuum compatible dc sputtering. Comparison of the results of the experiments and the simulations of magnetization curves revealed novel behavior, dominating the 90° coupling and the absence of 180° coupling. No clear oscillation, only a peak of the 90° coupling strength (J2∼-0.68 erg/cm2), was observed at tCr=1.2 nm. [ABSTRACT FROM AUTHOR]

Numerical simulation is carried out to investigate the magnetization process of epitaxial Co2MnSi/Cr/Co2MnSi trilayers with oscillatory interlayer exchange coupling. A series of the magnetization curves is successfully fitted by using a very simple model, in which the absent 180° coupling is assumed while 90° coupling and the lowest order cubic anisotropy are considered. The 90° coupling energy and the anisotropy constant can be uniquely determined, and it is revealed that the strength of 90° coupling decreases exponentially with the spacer layer thickness. [ABSTRACT FROM AUTHOR]

Fictive temperature (Tf) and fluorine (F)-doping concentration dependences of self-trapped holes (STHs) in silica glasses created by UV irradiation at low temperatures have been studied by the electron-paramagnetic-resonance method. It was found that the yield of STH decreases with decreasing Tf and increasing F-doping concentration. In combination with infrared spectra measurements, the correlation among Tf, F-doping concentration, Si–O bond length, and Si–O–Si bond angle was elucidated. We conclude that the change in both Tf and F doping can modify the network of SiO2 glass, leading to the suppression of the formation of STHs. [ABSTRACT FROM AUTHOR]