N. A. Gippius

Stark effect and polarizability in a single CdSe/ZnSe quantum dot

The quantum-confined Stark effect in a single self-assembled CdSe/ZnSe quantum dot was studied by means of highly spatially resolved photoluminescence spectroscopy. A nanotechnological approach making use of a capacitor-like geometry enabled us to apply a well-defined lateral electric field on the quantum dots. Stark shifts of up to 1.1 meV were obtained, which can be well fitted by a purely quadratic dependence on an electric field. In quite good agreement with theoretical calculations, an exciton polarizability of 4.9×10−3 meV/(kV/cm)2 can be extracted, while the permanent dipole moment in the lateral direction is found to be negligible.

Porous Si anisotropy from photoluminescence polarization

We report the observation of the anisotropic linear polarization of porous Si photoluminescence measured in two excitation geometries. In the normal excitation geometry (exciting beam normal to the sample (100) surface) linear luminescence polarization of as much as 20% is seen parallel to the excitation polarization. In the edge excitation geometry (exciting light incident on a cleaved edge of the sample) the luminescence polarization is aligned mainly in the [100] direction (normal to the surface). The effect is described within the framework of a dielectric model in which porous Si is considered as an aggregate of slightly deformed, elongated and flattened, dielectric elliptical Si nanocrystals with preferred orientation in the [100] direction.

Matched coordinates and adaptive spatial resolution in the Fourier modal method

Several improvements have been introduced for the Fourier modal method in the last fifteen years. Among those, the formulation of the correct factorization rules and adaptive spatial resolution have been crucial steps towards a fast converging scheme, but an application to arbitrary two-dimensional shapes is quite complicated.We present a generalization of the scheme for non-trivial planar geometries using a covariant formulation of Maxwells equations and a matched coordinate system aligned along the interfaces of the structure that can be easily combined with adaptive spatial resolution. In addition, a symmetric application of Fourier factorization is discussed.

Tight-binding calculations of image charge effects in colloidal nanoscale platelets of CdSe

CdSe nanoplatelets show perfectly quantized thicknesses of few monolayers. They present a situation of extreme, yet well de ned quantum con nement. Due to large dielectric contrast between the semiconductor and its ligand environment, interaction between carriers and their dielectric images strongly renormalize bare single particle states. We discuss the electronic properties of this original system in an advanced tight-binding model, and show that Coulomb interactions, including self-energy corrections and enhanced electron-hole interaction, lead to exciton binding energies up to several hundred meVs.

Intrinsic detection efficiency of superconducting nanowire single-photon detectors with different thicknesses

We evaluate experimentally the intrinsic detection efficiency (IDE) of superconducting NbN nanowire single-photon detectors in the range of wire thicknesses from 4 to 12 nm. The study is performed in the broad spectral interval between near-ultraviolet (wavelength 400 nm) and near-infrared (wavelength 2000 nm) light with plane waves at normal incidence. For visible light the IDE of the thinnest detectors reaches 70%. We use numerically computed absorptance of the nanowire-structures for the analysis of the experimental data. Variations in the detection efficiency with both the wire thickness and the wavelength evidence the red boundary of the hot-spot photon-detection mechanism. We explain the detection at larger wavelengths invoking thermal excitation of magnetic Pearl vortices over the potential barrier at the edges of the wire.

Binding energy of charged excitons in ZnSe-based quantum wells

Excitons and charged excitons (trions) are investigated in ZnSe-based quantum well structures with (Zn,Be,Mg)Se and (Zn,Mg)(S,Se) barriers by means of magneto-optical spectroscopy. Binding energies of negatively

Derivation of plasmonic resonances in the Fourier modal method with adaptive spatial resolution and matched coordinates

{(X}^{\ensuremath{-}})

Excitons in near-surface quantum wells in magnetic fields: Experiment and theory

and positively

Transverse photovoltage induced by circularly polarized light.

{(X}^{+})

Resonant mode coupling of optical resonances in stacked nanostructures.

charged excitons are measured as functions of quantum well width, and free carrier density and in external magnetic fields up to 47 T. The binding energy of