Clare C. Byeon

Directional control of surface plasmon polariton waves propagating through an asymmetric Bragg resonator

We have demonstrated the directional control of surface plasmon polariton (SPP) waves propagating through an asymmetric plasmonic Bragg resonator using femtosecond temporal-phase control via the resonant coupling of SPPs and the interference of SPPs. The near-field images display significant temporal-phase dependence, switching between left and right propagation after the Bragg resonator. Our results would be a key step toward the control of surface plasmon propagation direction in nanoscaled plasmonic applications

Channel-selective wavelength conversion and tuning in periodically poled Ti:LiNbO 3 waveguides

All-optical wavelength-selective single- and dual-channel wavelength conversion and tuning has been demonstrated in a periodically poled Ti:LiNbO(3) waveguide that has two second-harmonic phase-matching peaks by cascaded sum and difference frequency generation (cSFG/DFG). The wavelength conversion efficiency was measured to be -7 dB with coupled pump power of 233 mW.

PURITY MEASUREMENT OF SINGLE-WALLED CARBON NANOTUBES BY UV-VIS-NIR ABSORPTION SPECTROSCOPY AND THERMOGRAVIMETRIC ANALYSIS

We measured the content of single-walled carbon nanotubes (SWCNTs) in SWCNT soot within 3.7% error using UV-VIS-NIR absorption spectroscopy. We also propose a better overall evaluation method by combining thermogravimetic analysis with UV-VIS-NIR absorption spectroscopy to analyze the purity of SWCNT providing the accurate assessment of the amounts of noncarbonaceous impurity, carbonaceous impurity, and SWCNT each with respect to a highly purified reference.

GaAs quantum dots with a high density on a GaAs (111)A substrate

The GaAs quantum dots (QDs) on an AlGaAs∕GaAs (111)A surface grown by a droplet epitaxy have a density of 1.6×1011∕cm2, which is relatively higher than those (1.3×1010∕cm2) on an AlGaAs∕GaAs (001) surface. The formation of highly dense GaAs QDs on the (111)A surface can be explained by the relatively short surface migration of Ga atoms. The GaAs QDs on AlGaAs∕GaAs (111)A showed the intense photoluminescence (PL) and a relatively narrower PL linewidth compared to that of the GaAs QDs on AlGaAs∕GaAs (001), indicating that the QDs on the GaAs (111)A substrate have a high crystal quality and high uniformity than those on GaAs (001).

Polarization selection rules and optical transitions in terbium activated yttrium tantalate phosphor under x-ray, vacuum-ultraviolet, and ultraviolet excitations

The terbium-activated yttrium tantalite (YTaO(4):Tb(3+)) phosphor is of great interest due to the interesting spectroscopic properties of rare earth ions in crystals and also practical use in x-ray imaging. Using the group-theoretical approach, we analyze the selection rules for the transition between Stark components of Tb(3+) in symmetry of the actual crystal field and the polarization for the allowed transitions. The luminescence upon UV, vacuum-ultraviolet (VUV), and x-ray excitation is presented and discussed. The YTaO(4):Tb(3+) phosphors are found to be efficient VUV-excited luminescent materials that could be used not only in x-ray intensifying screens, but also in mercury-free fluorescent lamps or plasma display panels.

Femtosecond phase control of spatial localization of the optical near-field in a metal nanoslit array

We demonstrate spatial control of optical near-fields by femtosecond phase shaping in one-dimensional plasmonic structures. The near-field images display striking temporal-phase dependence, switching between double- and single-peak images within one lattice constant. The change of the near-field distribution is studied in the time and spectral domain. The spectral composition change observed by varying the time delay between two phase-locked femtosecond pulses explains the spatial control of the near-field images. Modal expansion calculations of linear light transmission using the surface impedance boundary condition are in excellent agreement with experiments.

Efficient multiphase green phosphor based on strontium thiogallate

Efficient multiphase green phosphors based on strontium thiogallate were synthesized by solid state reaction at 900–1000 °C with carbon as a reduction atmosphere. The detailed x-ray diffraction analysis, energy dispersive spectroscopy, Raman spectroscopy, and photoluminescence were carried out in order to enlarge the understanding of the radiative processes in multiphase green phosphors based on strontium thiogallate. The crystal field splitting, Stokes shift, redshift, and centroidal shift were estimated, and the results are in good agreement with mathematical calculations. Our study confirms that the proposed multiphase green phosphor based on strontium thiogallate is a good candidate for solid state lighting and display devices with higher intensity and better chromaticity coordinates in comparison with the known commercial phosphors.

Electric field dependent photoluminescence studies of nanoparticle sensitized photorefractive polymers

Electric field dependent photoluminescence studies of nanoparticle sensitized photorefractive polymer composites are reported. The composites comprise the charge transporting matrix poly(N-vinylcarbazole), the dye 1-(2′-ethylhexyloxy)-2,5-dimethyl-4-(4-nitrophenylazo) benzene, and either CdSe or CdSe∕ZnS core/shell nanoparticles. For the CdSe composite, application of a strong electric field causes a change in the photoluminescence intensity that continuously varies from −1% at the low energy end of the emission band to +1% at the high energy end. In contrast, the change in photoluminescence observed for the CdSe∕ZnS composite subject to the same field is −4% across the entire spectrum. These results show that photoliberated holes recombine with negatively charged nanoparticles both by capture into the excitonic ground state and via some other nonradiative route. Further, the addition of a ZnS shell to an otherwise similar nanoparticle reduces the number of holes captured into the excitonic ground state a...

Relative Content Evaluation of Single-walled Carbon Nanotubes using UV-VIS-NIR Absorption Spectroscopy

We propose an evaluation method of the relative content of single-walled carbon nanotubes (SWCNT) in SWCNT soot synthesized by arc discharge using UV-VIS-NIR absorption spectroscopy. In this method, we consider the absorbance of semiconducting and metallic SWCNTs together to calculate the relative content of SWCNTs with respect to a highly purified reference. Our method provides the more reliable and realistic evaluation of SWCNT content with respect to the whole carbonaceous content than the previously reported method. Keywords : Carbon nanotube, Purity measurement, UV-VIS-NIR absorption

Electromagnetically Induced Transparency on Semiconductor Quantum Well Structure

We observed electromagnetically induced transparency on GaAs/AlGas quantum well structure. EIT signal was observed at various conditions including delay time, coupling beam intensity, polarization state of probe-coupling beam and temperature.