Showing papers by "Din Ping Tsai published in 2005"

Study of optical recording bits by scanning surface potential microscopy

Abstract: We demonstrate a convenient method for the determination of recording bits in phase-change media based on scanning surface potential microscopy using a conductive tip. Commercially available digital versatile disks(DVD)±rewritable(RW) with initialization process are measured in experiments. The minimum size of the recording bits of DVD+RW, written by a commercial recorder, is around 425.22 nm. The mean work function (WF) value of the recording layer is found to be 4.27 eV from the contact potential difference images. After writing by a read∕write disk tester, the mean WF value of the amorphous bits has a drop of 15.46 meV. The results indicate that surface electronic energy of recorded regions is raised due to the writing process.

Dynamics of Mitochondria and Mitochondrial Ca2+ near the Plasma Membrane of PC12 Cells: A Study by Multimode Microscopy

Abstract: The goal of this study is to examine whether there is a difference in the regulation of Ca 2 + between mitochondria near the cell surface and mitochondria in the cytosol. Total Internal reflection fluorescence and epifluorescence microscopy were used to monitor changes in the mitochondrial Ca 2 + ([Ca 2 + ] m t ) between the mitochondria near the plasma membrane and those in the cytosol. The results show that [Ca 2 + ] m t near the plasma membrane increased earlier and decayed slower after high K + stimulation than average mitochondria in the cytosol. In addition, the changes in [Ca 2 + ] m t in the mitochondria near the cell surface after a second stimulation were larger than those induced by the first stimulation. The results provide direct evidence to support the hypothesis that mitochondria in different subcellular localization show differential responses to the influx of extracellular Ca 2 + .

Influence of near-field electromagnetic interactions on optical properties of perfect lens consisting of left-handed material

Abstract: In this paper, we investigate the surface plasma resonance of a slab of left-handed material (LHM). We use the transfer matrix method to calculate the attenuated total reflection spectra of the LHM slab. The intrinsic parameters of the LHM slab are suitable chose so that the slab has both negative permittivity and permeability in a frequency range of visible light. We have calculated the cases with different slab thickness and various dielectrics surrounding the LHM slab.

Far-field optical response of localized near-field enhancements induced by nano scatters in AgOx super-resolution near-field structure

Abstract: The super-resolution near-field structure (super-RENS) is an ultrahigh-density near-field optical disk data storage medium which can achieve superior spatial resolution. Our previous studies found that enhanced local optical intensity occurred at the near field of the super-RENS disk, and the nonlinear near-field optical enhancement is related to the localized surface plasmons of silver clusters dissociated from the AgO x layer of the super-RENS disk. In this paper, we report the near-field and far-field properties of AgO x -type super-RENS with different embedded silver nanoparticles using two-dimensional finite-difference time-domain (FDTD) calculations. Highly localized enhancements are found between adjacent silver nanoparticles in the near fields. The far-field signals of different types silver nano scatters confirm the super-resolution capability of AgO x -type Super-RENS disks. The behaviors of far-field signals indicate the correlation between the enhanced localized surface plasmons and the super-resolution capabilities of AgO x -type super-RENS.

Advanced imaging of nanometer-scale recorded bits on super-resolution near-field optical disk

Abstract: An advanced imaging technique is demonstrated for fast, non-destructive and high resolution characterizations for nanometer-scale recorded bits on a super-resolution near-field optical disk (super-RENS). For the first time, an array of individual 100 nm recorded marks is imaged and studied by using the conductive-atomic force microscopy (C-AFM) method. Discussions also include comparisons of 300 nm, 200 nm and 100 nm recorded marks on both a super-RENS disk and a commercial DVD disk, and the image results are evidence of the high carrier-to-noise ratio (CNR) value on the super-RENS disk, even though the mark size has been shrunk to less than the diffraction limit.

Z-scan nonlinear optical properties of the Au-SiO2 nanocomposite thin film

Abstract: Au-SiO2 nanocomposite thin film is fabricated reproducibly by co-sputtering method with the size of Au nano particles around 2 to 10 nm. TEM images display the irregular shape Au nanoparticles are embedded in SiO2 thin film with random distribution. A surface plasmon absorption peak of Au nanoparticles is found in absorption spectra. The nonlinear optical properties are measured by confocal Z-scan method with a sub-nanosecond pulse laser (λ=532nm, pulse width 0.71ns, repetition rate 15.79kHz) and high-numerical-aperture objective lens (NA=0.55). Results of the Z-scan show nonlinear optical properties and enhanced transmittance at the focusing position of nanocomposite Au-SiO2 films. The transmittance can be more than 135% for a 15-nm-thick Au-SiO2 nanocomposite thin film with an average grain size of around 5 nm.

Optimum instrumentation of a tapping mode, non-optically regulated near-field scanning optical microscope and its applications

Abstract: We describe the optimum design of the near-field scanning optical microscope (NSOM) based on a short probe tapping mode tuning-fork (TMTF) configuration and its applications in optoelectronic characterization and optical measurements. The short probe TMTF-NSOM is constructed to operate both in collection and excitation modes, in which a cleaved short fiber probe attached to one tine of the tuning fork is used as the light collector/emitter as well as the force sensing element. Interference fringes due to standing evanescent waves generated by total internal reflection are imaged by collection mode. On the other hand, excitation mode of short probe TMTF-NSOM is applied to perform near-field surface photovoltage measurements on AlGaInP light emitting diode structures.

Size effects of localized surface plasmon induced by embedded silver nanoparticles in near-field optical disk

Abstract: In this paper, we report the near-field and far-field properties of AgOx-type super-resolution near-field structure with embedded silver nanoparticles of different sizes using two-dimensional finite-difference timedomain calculations Highly localized enhancements were found near the surface of nanoparticles, and the near-field enhancements increased with the size of nano particles The far-field difference signals of silver nano scatters confirm the super-resolution capability, and the difference signals were stronger for larger nanoparticles The behaviors of far-field signals indicate the correlation between the enhanced localized surface plasmons and the super-resolution capabilities