X-ray mapping in a scanning transmission electron microscope of InGaAs quantum dots with embedded fractional monolayers of aluminium

We investigate AlGaAs/GaAs superlattices as well as InGaAs/GaAs quantum wells (QWs) and epitaxial quantum dots (QDs) where during the molecular beam epitaxy of InGaAs QDs the aluminium flux cell was opened briefly to incorporate fractional monolayers of Al into the InGaAs. We show that X-ray mapping with a large collection angle is capable to detect 0.3-0.4 fractional Al monolayers with a resolution of just under 1nm

Trench width dependant deeply etched surface-defined InP gratings for low-cost high speed DFB/DBR

In this paper we are reporting a fabrication process for multi-section telecom lasers based on surface defined lateral gratings, which is compatible with low-cost high-throughput nano-imprint lithography. A new grating definition process is developed, which allow a better control of the cross section geometry to obtain higher coupling strength

Coupled-mode theory for Bose-Einstein condensates

We apply the concepts of nonlinear guided-wave optics to a Bose-Einstein condensate (BEC) trapped in an external potential. As an example, we consider a parabolic double-well potential and derive coupled-mode equations for the complex amplitudes of the BEC macroscopic collective modes. Our equations describe different regimes of the condensate dynamics, including the nonlinear Josephson effect for any separation between the wells. We demonstrate macroscopic self-trapping for both repulsive and attractive interactions, and confirm our results by numerical simulations.Comment: 4 pages, 5 figures; typos removed, figures amended; submitted to PR

Scattering of dipole-mode vector solitons: Theory and experiment

We study, both theoretically and experimentally, the scattering properties of optical dipole-mode vector solitons - radially asymmetric composite self-trapped optical beams. First, we analyze the soliton collisions in an isotropic two-component model with a saturable nonlinearity and demonstrate that in many cases the scattering dynamics of the dipole-mode solitons allows us to classify them as ``molecules of light'' - extremely robust spatially localized objects which survive a wide range of interactions and display many properties of composite states with a rotational degree of freedom. Next, we study the composite solitons in an anisotropic nonlinear model that describes photorefractive nonlinearities, and also present a number of experimental verifications of our analysis.Comment: 8 pages + 4 pages of figure

Optical and Spin Properties of NV Center Ensembles in Diamond Nano Pillars

Nitrogen vacancy NV color centers in diamond are excellent quantum sensors possessing high sensitivity and nano scale spatial resolution. Their integration in photonic structures is often desired, since it leads to an increased photon emission and also allows the realization of solid state quantum technology architectures. Here, we report the fabrication of diamond nano pillars with diameters up to 1000 nm by electron beam lithography and inductively coupled plasma reactive ion etching in nitrogen rich diamonds type Ib with [100] and [111] crystal orientations. The NV centers were created by keV He ion bombardment and subsequent annealing, and we estimate an average number of NVs per pillar to be 4300 300 and 520 120 for the [100] and [111] samples, respectively. Lifetime measurements of the NVs excited state showed two time constants with average values of amp; 964;1 amp; 8776; 2 ns and amp; 964;2 amp; 8776; 8 ns, which are shorter as compared to a single color center in a bulk crystal amp; 964; amp; 8776; 10 ns . This is probably due to a coupling between the NVs as well as due to interaction with bombardment induced defects and substitutional nitrogen P1 centers . Optically detected magnetic resonance measurements revealed a contrast of about 5 and average coherence and relaxation times of T2 [100] 420 40 ns, T2 [111] 560 50 ns, and T1 [100] 162 11 amp; 956;s, T1 [111] 174 24 amp; 956;s. These pillars could find an application for scanning probe magnetic field imagin

Do coastal wetlands drive or buffer coastal acidification?

peer reviewe

Pseudomorphe InGaAs/Ga(Al)As Heterostrukturen: Wachstum und Charakterisierung

SIGLEAvailable from TIB Hannover: DW 1315 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Magnetic field control of the neutral and charged exciton fine structure in single quantum dashes emitting at 1.55 μ m

This research was supported by the Polish Ministry of Science and Higher Education/the National Science Center Grant No. 2011/02/A/ST3/00152. S.H. gratefully acknowledges support by the Royal Society and the Wolfson Foundation.We investigated the neutral and charged exciton fine structure in single InAs/InGaAlAs/InP quantum dashes emitting at 1.55 μm using polarization-resolved microphotoluminescence in a magnetic field. Inverted spin configuration of horizontally [1-10] and vertically [110] polarized transitions has been observed. An in-plane magnetic field of up to 5 Tesla has been applied to tailor the fine structure, and eventually to reduce the splitting of the bright exciton states down to zero. This inverted structure has been observed for all the investigated excitons, making it a characteristic feature for this class of nanostructures with the largest splitting reduction of 170 μeV.Publisher PDFPeer reviewe