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We demonstrate spin‐polarization of the nuclei in self‐assembled InGaAs quantum dots due to electrical injection of a spin‐polarized current. High‐resolution optical spectroscopy of the Overhauser shift is used as detection method. The electrically induced spin‐polarization is of comparable magnitude as for spin‐injection by photoexcitation. The results imply that efficient nuclear spin‐polarization in quantum dots can be achieved by purely electrical means.

In this work we present experimental results on the behavior of random lasing modes found in nanocrystalline ZnO. The degree of mode localization which has already been discussed in theoretical works is probed by spatially resolved luminescence spectroscopy. We find strongly localized and extended modes coexisting in the same spatial area of our samples. Theory predicts localized modes to have a higher Q‐factor compared to the extended modes which is confirmed by our experiments since localized modes appear already for small optical gain while extended modes are only found in the presence of high optical gain. The spectral distance of spatially overlapping extended modes appears to be uniform. This mode spacing is predicted for strong modal interactions.

We investigated the effect of in‐situ thermal annealing on InAs quantum dots (QDs) grown site‐selectively on pre‐patterned GaAs substrates. We compare as grown and annealed samples. A morphological transition is observed where originally two QDs merge into one larger dot.

We present time‐resolved studies of the spin polarization dynamics during and after initialization through pulsed electrical spin injection into InGaAs quantum dots embedded in a p‐i‐n‐type spin‐injection light‐emitting diode. Experiments are performed with pulse widths in the nanosecond range and a time‐resolved single photon counting setup is used to detect the subsequent electroluminescence. We find evidence that the achieved spin polarization shows an unexpected temporal behavior, attributed mainly to many‐carrier and non‐equilibrium effects in the device.

An efficient light‐matter coupling requires high‐quality (Q) micro‐cavities with small mode volume. We suggest GaAs micro‐pyramids placed on top of AlAs/GaAs distributed Bragg reflectors to be promising candidates. The pyramids were fabricated by molecular‐beam epitaxy, electron‐beam lithography and a subsequent wet‐chemical etching process using a sacrificial AlAs layer. Measured Q‐factors of optical modes in single pyramids reach values up to 650. A finite‐difference time‐domain simulation assuming a simplified cone‐shaped geometry suggests possible Q‐factors up to 3600. To enhance the light confinement in the micro‐pyramids we intend to overgrow the pyramidal facets with a Bragg mirror—results of preliminary tests are given.

We discuss two different types of GaAs‐based microcavities: Single and coupled pillar‐type resonators with AlAs/GaAs distributed Bragg reflectors (DBRs) were fabricated by means of molecular‐beam epitaxy (MBE) and focussed‐ion‐beam (FIB) milling. The dependence of the observed cavity modes on the pillar diameter and on the coupling bridge were investigated. Additionally, we present an alternative cavity design consisting of a pyramidal GaAs resonator placed on top of an AlAs/GaAs DBR. Single or even coupled pyramids were achieved by combining electron‐beam lithography and wet chemical etching. In(Ga)As quantum dots (QDs) served as a broad‐band light source at around 950 nm.

This paper describes a new monochromator design for a bending magnet beamline of the Swiss Light Source synchrotron facility. The beamline optics is based on a horizontally deflecting spherical grating monochromator (SGM) with two gratings at a constant deviation angle. It covers a photon energy range from 200 eV to 1000 eV. This paper concentrates on the original flexure‐based mechanisms with partially parallel kinematics invented and designed for this monochromator, as well as on the lessons learned from the assembly and testing of the system.

We have studied temperature dependence of the signals of optical orientation of excitons at resonant excitation of the ensemble of planar self‐assembled CdSe/ZnSe quantum dots and show that spin memory in this system survives up to 100K. To describe the experimental results we apply the model that considers explicitly the effect of multi‐phonon processes on the broadening of bright‐exciton‐phonon sublevels and demonstrate that calculated temperature dependences of spin relaxation rates are in good agreement with obtained experimental data.

he temperature dependence of photoluminescence spectra of ultrathin ZnCdSe/ZnSe quantum wells with inhomogeneous Cd distribution indicates that there are two types of emitting states (metastable and ground), which contribute to the high‐energy and low energy part of the PL band, respectively. Optical orientation and optical alignment experiments at resonant excitation show that considerable part of islands contains an extra electron. As a result, the deepest states of islands are formed mostly by the ground states of trions while the metastable states in charged island correspond to the exciton states spatially isolated from localized electron.

The temporal dynamics of the exciton photoluminescence (PL) in ZnO nanorod samples was investigated experimentally as a function of temperature and excitation intensity. Excitonic photoluminescence is observed up to room temperature. The excitation dependence of the PL dynamics reveals a saturable non‐radiative recombination center. Under high excitation conditions the time‐resolved photoluminescence shows two components: the ZnO M‐band which decays with a temperature independent sub‐100 ps time constant, and the intrinsic exciton PL with a time constant of several 100 ps increasing with temperature. Exciton‐exciton scattering effects are notably absent, which is attributed to the reduced polariton phase space resulting from the small nanorod diameter of 50 nm.