T. Sugimoto

Effect of surface plasmon resonance on the optical activity of chiral metal nanogratings.

We examine the mechanism responsible for the optical activity of a two-dimensional array of gold nanostructures with no mirror symmetry on a dielectric substrate. Measurements with different incident angles, polarizations and sample orientations allow us to reveal that observed polarization effect is enhanced by surface plasmon resonance. By performing numerical simulation with rigorous diffraction theory we also show that the grating chirality can be described in terms of the non-coplanarity of the electric field vectors at the front (air-metal) and back (substrate-metal) sides of the grating layer.

Near-field coherent excitation spectroscopy of InGaAs/GaAs self-assembled quantum dots

Using near-field optical microscopy, we have performed coherent excitation spectroscopy of self-assembled quantum dots (SAQDs). A pair of coherent pulses with a time delay between them allows measurement of the temporal coherence of the carrier wave function in single quantum dots. The observed decoherence time is about 15 ps and is well explained by resonant Raman scattering of phonons. Furthermore, quantum beats originating from the superposition of two closely spaced coherent states have been observed. This opens up possibilities of quantum mechanical control of the carrier wave function in SAQDs.

Formation and optical properties of GaSb quantum dots epitaxially grown on Si substrates using an ultrathin SiO2 film technique

We developed a technique for forming epitaxial GaSb quantum dots on Si substrates using ultrathin SiO2 films that contain epitaxial Ge nuclei. Unlike Volmer–Weber-type GaSb quantum dots on Si, the dot density was higher (109–1012 cm−2) and the dot size was controlled in the range of approximately 10–100 nm. The nucleation of quantum dots was initiated by trapping Ga atoms on the Ge nuclei. Photoluminescence spectroscopy measurement at 5 K revealed the quantum-confinement effect in GaSb dots causing the photoluminescence peak to be continuously blueshifted from 0.76 eV by ∼30 meV when the base length of the dots decreases from 100 to 17 nm.

Fermi surfaces and orbital polarization in superconducting CeO0.5 F0.5BiS2 revealed by angle-resolved photoemission spectroscopy

We have investigated the electronic structure of BiS

Observation of dip structures in PLE spectra of a highly excited single self-assembled quantum dot

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Localized and mixed valence state of Ce 4f in superconducting and ferromagnetic CeO1-x FxBiS2 revealed by x-ray absorption and photoemission spectroscopy

-based CeO

Metallic phase in stoichiometric CeOBiS 2 revealed by space-resolved ARPES

_{0.5}

Electronic structure of Li

F

_{1+x}

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[Mn

BiS