K. Edamatsu

Measurement of the photonic de broglie wavelength of entangled photon pairs generated by spontaneous parametric down-conversion.

Using a basic Mach-Zehnder interferometer, we demonstrate experimentally the measurement of the photonic de Broglie wavelength of entangled photon pairs (biphotons) generated by spontaneous parametric down-conversion. The observed interference manifests the concept of the photonic de Broglie wavelength. We also discuss the phase uncertainty obtained from the experiment.

Quantum diffraction and interference of spatially correlated photon pairs generated by spontaneous parametric down-conversion

We demonstrate one- and two-photon diffraction and interference experiments utilizing parametric down-converted photon pairs (biphotons) and a transmission grating. With two-photon detection, the biphoton exhibits a diffraction-interference pattern equivalent to that of an effective single particle that is associated with half the wavelength of the constituent photons. With one-photon detection, however, no diffraction-interference pattern is observed. We show that these phenomena originate from the spatial quantum correlation between the down-converted photons.

A new approach to ZnCdSe quantum dots

Abstract We propose a new approach of fabricating ZnCdSe quantum dots (QDs) on ZnSe and GaAs (110) surfaces by simply depositing a ZnSe/ZnCdSe/ZnSe heterostructure. The growth conditions are selected to introduce surface roughness on the over grown ZnSe which allows the formation of ZnCdSe QDs. Optical studies unambiguously demonstrate the formation of QDs. Resolution-limited sharp emission lines are observed by micro-photoluminescences and the linewidths are much less than the thermal energy. As time goes on, intermittent behaviors of the QD emissions are observed. A proper selection of growth conditions is essential in obtaining ZnCdSe QDs by this method, especially on GaAs (110) surfaces.

Intermittent photoluminescence and thermal ionization of ZnCdSe/ZnSe quantum dots grown by molecular beam epitaxy

We report the intermittent photoluminescence of ZnCdSe quantum dots (QDs) embedded in a ZnSe matrix grown by molecular beam epitaxy. The luminous time of the QD is strongly dependent on temperature but not on excitation intensity. This indicates that the ionization of the QDs is determined predominantly by thermal excitation of carriers into the ZnSe matrix.

Observation of local light propagation in ordered latex layers by scanning near-field optical microscope

Abstract Under the local excitation by a scanning near-field optical microscope, we have observed the transmission and luminescence excitation images of the hexagonally close-packed single layers of ordered, dye-doped polystyrene particles (LATEX) of 1.0 and 0.37 μm in diameter. The transmission images with the spatial resolution shorter than the optical wavelength dramatically changes, depending not only on the diameter of the particles but also on the aperture size of the probe tip end of the microscope. The luminescence excitation images for the single layers composed of particles, all or a part of which is dye-doped, give the information how the excitation light propagates through the layers. From these results we propose that the localized and extended modes of electromagnetic waves with large wave vectors propagating across and along the layers, respectively, are generated under the local excitation by the near-field effect

Spontaneous formation and photoluminescence of ZnSe dot arrays

Highly luminescent ZnSe quantum dot arrays (QDAs) are spontaneously formed on cleavage-induced GaAs (110) surfaces. The QDAs are configured for their preferred growth on the step top. The confinement on carriers results from the difference in the band gaps of the strained ZnSe layer and the strain-relaxed ZnSe QDA. In contrast to other emissions from the ZnSe layer, the linewidth of the QDA emission is dependent neither on temperature nor on excitation intensity. Moreover, the energy position of the QDA emission is stable even at high excitations. These results reflect the δ functionlike density of states of the QDAs. This letter suggests a novel approach to semiconductor QDs and QDAs.

Self-Assembled Polystyrene Microparticle Layers as Two-Dimensional Photonic Crystals

Abstract Optical properties of ordered polystyrene microsphere layers have been investigated and the results are discussed in terms of the two-dimensinal photonic band effect.

Excited-state absorption of excitons confined in CuCl quantum dots

We have investigated infrared transient absorption spectra under size-selective excitation of CuCl QDs embedded in NaCl matrices. The transient absorption consists of mainly two decay components. The spectra for the faster one, ascribed to the transition from the 1S-exciton to the 2P states, show a peak energy shift depending on the dot size. The results indicate that the Rydberg energy of the confined exciton has a size dependency. A comparison between the experimental data and a theoretical calculation has been carried out. The slower component does not depend much on the dot size and shows an anomalous long-lived time at low temperature. The properties of this slower component are also discussed.

Confined Multiexciton States of GaAs/AlGaAs Quantum Dots Grown on a (411)A GaAs Surface

We have investigated the micro photoluminescence (micro-PL) spectra of a single GaAs/AlGaAs quantum dot (QD) grown on a (411)A GaAs substrate, and observed sharp luminescence lines. These luminescence lines are classified into three types in terms of their excitation-power dependence. For one of them the intensity increases linearly with excitation power density, and the others that appear at the lower and higher energy sides of the linear one exhibit superlinear dependence, The difference in the excitation-power dependence reflects the number of excitons created in a QD, namely, the linear dependence originates from the lowest state of a confined exciton, and the others from biexcitonic and multiple exciton states.

Two-photon excitation and luminescence of confined excitons in CuCl nanocrystals

Abstract We investigated two-photon excitation and subsequent emission due to confined excitons of CuCl nanocrystals embedded in NaCl matrices. The resonant emission spectra indicate the existence of ‘two-photon resonant luminescence’ and ‘secondharmonic scattering’. The excitation spectra exhibit sharp increase which may be assigned to the transitions into higher Coulombic states (nP) of the confined excitons.