Light Controlled Optical Aharonov-Bohm Oscillations in a Single Quantum Ring.

We found that optical Aharonov-Bohm oscillations in a single GaAs/GaAlAs quantum ring can be controlled by excitation intensity. With a weak excitation intensity of 1.2 kW cm, the optical Aharonov-Bohm oscillation period of biexcitons was observed to be half that of excitons in accordance with the period expected for a two-exciton Wigner molecule.

Quasi-one-dimensional density of states in a single quantum ring.

Generally confinement size is considered to determine the dimensionality of nanostructures. While the exciton Bohr radius is used as a criterion to define either weak or strong confinement in optical experiments, the binding energy of confined excitons is difficult to measure experimentally. One alternative is to use the temperature dependence of the radiative recombination time, which has been employed previously in quantum wells and quantum wires.

Amplified all-optical polarization phase modulator assisted by a local surface plasmon in Au-hybrid CdSe quantum dots.

We propose an amplified all-optical polarization phase modulator assisted by a local surface plasmon in Au-hybrid CdSe quantum dots. When the local surface plasmon of a spherical Au quantum dot is in resonance with the exciton energy level of a CdSe quantum dot, a significant enhancement of the linear and nonlinear refractive index is found in both the real and imaginary terms via the interaction with the dipole field of the local surface plasmon. Given a gating pulse intensity, an elliptical polarization induced by the phase retardation is described in terms of elliptical and rotational angles.

Sub-picosecond spin relaxation of bright excitons and imbalance suppression in asymmetric Cdse/Zns nanocrystal quantum dots under an applied magnetic field.

The ultrafast spin dynamics of the bright exciton in CdSe/ZnS nanocrystal quantum dots has been investigated using a circularly polarized pump-probe experiment. A remarkably fast spin flip (-500 fs) of the bright exciton was observed at 4 K, which is attributed to the anisotropic electron-hole exchange interaction and the random positioning of nanocrystal quantum dots. In the presence of an applied magnetic field (5 T), the exciton spin parallel to the external magnetic field was favored due to Zeeman splitting.

Observation of red-shifted strong surface plasmon scattering in single Cu nanowires.

Surface plasmon scattering spectra of chemically produced single Cu nanowires were obtained using a total internal reflection microscope. In particular, we have observed a strong surface plasmon peak in the far red and a red-shift of the surface plasmon resonance with increasing nanowire diameter. We believe that the most reasonable origin for the red-shift of comparably large diameter nanowires is the phase retardation effect.

Local field-induced optical properties of Ag-coated CdS quantum dots.

Local field-induced optical properties of Ag-coated CdS quantum dot structures are investigated. We experimentally observe a clear exciton peak due to the quantum confinement effect in uncoated CdS quantum dots, and surface plasmon resonance and red-shifted exciton peak in Ag-coated CdS composite quantum dot structures. We have calculated the Stark shift of the exciton peak as a function of the local field for different silver thicknesses and various sizes of quantum dots based on the effective-mass Hamiltonian using the numerical-matrix-diagonalization method.