Articles you may be interested inA two-in-one superhydrophobic and anti-reflective nanodevice in the grey cicada Cicada orni (Hemiptera) J. Appl. Phys. 116, 024701 (2014); 10.1063/1.4889849 AlInP-based rolled-up microtube resonators with colloidal nanocrystals operating in the visible spectral range Appl. 4 Gesellschaft zur Förderung von Medizin-, Bio-, und Umwelttechnologien (GMBU) e.V.,

Suzuki-Miyam~polycondensatlbn of 2-(4A,5;5-tetramethyI-lJ3,2-dioxaborolan-2-yl)-7-broino~9,9-dioctylfluor~ ene in aqueous miniemulsion With only tw'oequivalents of NaOH as~ base yields colloidally stable nanoparticles of polyfluorene With M;, ca. 2 X lQ4 g mol-1 and particle sizes of 40-85 nrn,depending on the surfactant concentration. Polymerization in the presen<:e of CdSe/CdS core/shell quantum dots affords hybrid nanoparticles of nonaggregated qllantum dots, in particular nanoparticles composed of a single quantllm dot embedded in a polyfluorene shell. Microphotolurninescence $pectros.copy on single hybrid. particles reveals an enhanced photostability of the quantllm dots and indicates an etIkient Forster energy transfer from the polyfluorene shell to the quantum dot.

The authors study the interaction of complementary terahertz (THz) split ring resonators with THz surface plasmon polaritons (SPPs) as a function of the meta-atom distance. The THz transmission properties of 15 samples for which the array dimensions are varied keeping the resonator shape constant are investigated. The linewidth of the inductive-capacitive (LC-)resonance is decreasing with increasing meta-atom distance, up to the frequency matching with the first SPP-mode. The SPP-mode couples to the narrow LC-resonance leading to an anti-crossing of the modes. In contrast, the narrow SPP-mode tunes across the broader dipole-like mode in orthogonal polarization. The excitation direction of the SPP-mode is found to lie along the electric field polarization of the THz. www.advopticalmat.de Figure 5. a) Normalized transmission spectra as a function of the lattice constant with a x = a y for the broad dipole-mode excited in x-direction. The calculated SPP-modes that cross the broad dipole-mode are traced in blue solid lines after Equation (2). Black sections denote not sampled lattice constants. The normalized transmission of the dipole-mode as function of the frequency is shown for square lattices in b) for a x = a y = 70 µm and c) for a x = a y = 85 µm. Transmission spectra of rectangular lattices are shown for d) a x = 70 µm and a y = 85 µm and for e) a x = 85 µm and a y = 70 µm.

We study the dynamics of photoexcited electrons and holes in single negatively charged CdSe/ZnSe quantum dots with two-color femtosecond pump-probe spectroscopy. An initial characterization of the energy level structure is performed at low temperatures and magnetic fields of up to 5 T. Emission and absorption resonances are assigned to specific transitions between few-fermion states by a theoretical model based on a configuration interaction approach. To analyze the dynamics of individual charge carriers, we initialize the quantum system into excited trion states with defined energy and spin. Subsequently, the time-dependent occupation of the trion ground state is monitored by spectrally resolved differential transmission measurements. We observe subpicosecond dynamics for a hole excited to the D shell. The energy dependence of this D-to-S shell intraband transition is investigated in quantum dots of varying size. Excitation of an electron-hole pair in the respective p shells leads to the formation of singlet and triplet spin configurations. Relaxation of the p-shell singlet is observed to occur on a time scale of a few picoseconds. Pumping of p-shell triplet transitions opens up two pathways with distinctly different scattering times. These processes are shown to be governed by the mixing of singlet and triplet states due to exchange interactions enabling simultaneous electron and hole spin flips. To isolate the relaxation channels, we align the spin of the residual electron by a magnetic field and employ laser pulses of defined helicity. This step provides ultrafast preparation of a fully inverted trion ground state of the quantum dot with near unity probability, enabling deterministic addition of a single photon to the probe pulse. Therefore our experiments represent a significant step towards using single quantum emitters with well-controled inversion to manipulate the photon statistics of ultrafast light pulses.

The photoluminescence emission by mesoscopic condensed matter is ultimately dictated by the fine-structure splitting of the fundamental exciton into optically allowed and dipole-forbidden states. In epitaxially grown semiconductor quantum dots, nonradiative equilibration between the fine-structure levels is mediated by bulk acoustic phonons, resulting in asymmetric spectral broadening of the excitonic luminescence. In isolated colloidal quantum dots, spatial confinement of the vibrational motion is expected to give rise to an interplay between the quantized electronic and phononic degrees of freedom. In most cases, however, zero-dimensional colloidal nanocrystals are strongly coupled to the substrate such that the charge relaxation processes are still effectively governed by the bulk properties. Here we show that encapsulation of single colloidal CdSe/CdS nanocrystals into individual organic polymer shells allows for systematic vibrational decoupling of the semiconductor nanospheres from the surroundings. In contrast to epitaxially grown quantum dots, simultaneous quantization of both electronic and vibrational degrees of freedom results in a series of strong and narrow acoustic phonon sidebands observed in the photoluminescence. Furthermore, an individual analysis of more than 200 compound particles reveals that enhancement or suppression of the radiative properties of the fundamental exciton is controlled by the interaction between fine-structure states via the discrete vibrational modes. For the first time, pronounced resonances in the scattering rate between the fine-structure states are directly observed, in good agreement with a quantum mechanical model. The unambiguous assignment of mediating acoustic modes to the observed scattering resonances complements the experimental findings. Thus, our results form an attractive basis for future studies on subterahertz quantum opto-mechanics and efficient laser cooling at the nanoscale.