Atom holography

We study the conditions under which atomic condensates can be used as a recording media and then suggest a reading scheme which allows to reconstruct an object with atomic reading beam. We show that good recording can be achieved for flat condensate profiles and for negative detunings between atomic Bohr frequency and optical field frequency. The resolution of recording dramatically depends on the relation between the healing length of the condensate and the spatial frequency contents of the optical fields involved.Comment: 8 pages, 5 figures, Late

Unbound states in quantum heterostructures

We report in this review on the electronic continuum states of semiconductor Quantum Wells and Quantum Dots and highlight the decisive part played by the virtual bound states in the optical properties of these structures. The two particles continuum states of Quantum Dots control the decoherence of the excited electron – hole states. The part played by Auger scattering in Quantum Dots is also discussed

Dynamic Acoustic Control of Individual Optically Active Quantum Dot-like Emission Centers in Heterostructure Nanowires

We probe and control the optical properties of emission centers forming in radial het- erostructure GaAs-Al0.3Ga0.7As nanowires and show that these emitters, located in Al0.3Ga0.7As layers, can exhibit quantum-dot like characteristics. We employ a radio frequency surface acoustic wave to dynamically control their emission energy and occupancy state on a nanosec- ond timescale. In the spectral oscillations we identify unambiguous signatures arising from both the mechanical and electrical component of the surface acoustic wave. In addition, differ- ent emission lines of a single quantum dot exhibit pronounced anti-correlated intensity oscilla- tions during the acoustic cycle. These arise from a dynamically triggered carrier extraction out of the quantum dot to a continuum in the radial heterostructure. Using finite element modeling and Wentzel-Kramers-Brillouin theory we identify quantum tunneling as the underlying mech- anism. These simulation results quantitatively reproduce the observed switching and show that in our systems these quantum dots are spatially separated from the continuum by > 10.5 nm.Comment: This document is the unedited Author's version of a Submitted Work that was subsequently accepted for publication in Nano Letters, copyright \c{copyright} American Chemical Society after peer review. To access the final edited and published work see http://pubs.acs.org/doi/abs/10.1021/nl404043

Development of a transfer standard for laser thermometry

The measurement of gas temperatures is important in many combustion, chemical manufacturing and materials processing applications. Different laser spectroscopic methods are applied to measure the temperature of gases. Nevertheless, up to now none of these methods have been calibrated against the international temperature scale of 1990 (ITS-90). A transfer standard for laser thermometry (TSL) has been developed to calibrate laser thermometry techniques. The standard provides optical access to a sample volume of a gas maintained at a stable temperature within the range of 300 K to 1850 K. The gas temperature is measured using built-in, calibrated thermometers including thermocouples, Accufiber optical-fibre probes and an optical pyrometer for traceability to the ITS-90. Broadband Coherent Anti-Stokes Raman Scattering (CARS) and scanning CARS experiments have been performed inside the furnace. The measuring uncertainty of broadband CARS amounts to less than 4 per cent between room tempera ture and 800 K. At temperatures between 800 K and 1850 K an uncertainty of less than 2 per cent has been achieved. For scanning CARS the uncertainty and the precision amounts to 2 per cent between 295 K and 1850 K