25 research outputs found
Decay dynamics of neutral and charged excitonic complexes in single InAs∕GaAs quantum dots
No full textThis article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Appl. Phys. Lett. 92, 063116 (2008) and may be found at https://doi.org/10.1063/1.2844886.Systematic time-resolved measurements on neutral and charged excitonic complexes (, , +, and +) of 26 different single InAs∕GaAs quantum dots are reported. The ratios of the decay times are discussed in terms of the number of transition channels determined by the excitonic fine structure and a specific transition time for each channel. The measured ratio for the neutral complexes is 1.7 deviating from the theoretically predicted value of 2. A ratio of 1.5 for the positively charged exciton and biexciton decay time is predicted and exactly matched by the measured ratio indicating identical specific transition times for the transition channels involved.DFG, 43659573, SFB 787: Halbleiter - Nanophotonik: Materialien, Modelle, BauelementeEC/FP6/500101/EU/Self-Assembled semiconductor Nanostructures for new Devices in photonics and Electronics/SANDI
Large internal dipole moment in InGaN/GaN quantum dots
No full textThis article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Appl. Phys. Lett. 97, 063103 (2010) and may be found at https://doi.org/10.1063/1.3477952.Direct observation of large permanent dipole moments of excitonic complexes in InGaN/GaN quantum dots is reported. Characteristic traces of spectral diffusion, observed in cathodoluminescence of InGaN/GaN quantum dots, allow deducing the magnitude of the intrinsic dipole moment. Our experimental results are in good agreement with realistic calculations of quantum dot transition energies for position-dependent external electric fields.DFG, 43659573, SFB 787: Halbleiter - Nanophotonik: Materialien, Modelle, Bauelement
Correction to: Clinical and endovascular practice in interventional radiology: a contemporary European analysis
No full textUpon publication of this article (Kok et al., 2018), the authors noticed that author ‘Miguel Casares Santiago’ was spelt incorrectly. This has been corrected by means of this correction article
Cascaded emission of linearly polarized single photons from positioned InP/GaInP quantum dots
No full textThis content may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This material originally appeared in Appl. Phys. Lett. 103, 191113 (2013) and may be found at https://doi.org/10.1063/1.4828354.We report on the optical characterization of site-controlled InP/GaInP quantum dots (QDs). Spatially resolved low temperature cathodoluminescence proves the long-range ordering of the buried emitters, revealing a yield of ∼90% of optically active, positioned QDs and a strong suppression of emitters on interstitial positions. The emission of single QDs shows a pronounced degree of linear polarization along the [0,−1,1] crystal axis with an average degree of polarization of 94%. Photon correlation measurements of the emission from a single QD indicate the single-photon character of the exciton and biexciton emission lines as well as the cascaded nature of the photon pair
Epidural interlaminar injections in severe degenerative lumbar spine: Fluoroscopy should not be a luxury
No full textObjective: To assess technical efficacy, accuracy, and safety of epidural (interlaminar) injections performed blindly in patients with a severely degenerated lumbar spine. Methods: Over 12 consecutive months, 138 patients with a severe degenerative lumbar spine underwent epidural (interlaminar) injection as therapy for low back pain and neuralgia. Patients had already undergone a blind epidural infiltration with minimum or no pain reduction. The session was repeated in the angiography suite. Patients were placed in the lateral decubitus position. The injection was performed without image guidance by an anaesthesiologist; the target level was defined before the beginning of the procedure. Once air resistance loss was felt it was presumed that the needle was inside the epidural space. Verification of needle position was performed by injection of 1-3 mL of iodinated contrast medium under fluoroscopy in a lateral projection. Results: C orrect needle position inside the epidural space was documented in 82/138 cases (59.4%); unexpected extraepidural location was seen in 56/138 cases (40.6%). Target level was reached in 96/138 cases (69.6%); in 42/138 cases (30.4%) the needle was positioned in a non-target level. In 5/138 (3.6%) cases, there was inadvertent intradural position of the needle. Image guidance was subsequently used for correct positioning of the needle, which was feasible in all cases. Conclusion: Blind interlaminar epidural injections lack the accuracy of exact needle location that imaging guidance offers in approximately 40% of cases, when there is difficult spine anatomy and the initial epidural approach has failed to provide pain relief. Image guidance for interlaminar epidural injection ensures accurate needle placement, enhancing the safety and efficacy of the procedure. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved
Two-photon interference from remote deterministic quantum dot microlenses
No full textThis article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Appl. Phys. Lett. 110, 011104 (2017) and may be found at https://doi.org/10.1063/1.4973504.We report on two-photon interference (TPI) experiments using remote deterministic single-photon sources. Employing 3D in-situ electron-beam lithography, we fabricate quantum-light sources at specific target wavelengths by integrating pre-selected semiconductor quantum dots within monolithic microlenses. The individual single-photon sources show TPI visibilities of 49% and 22%, respectively, under pulsed p-shell excitation at 80 MHz. For the mutual TPI of the remote sources, we observe an uncorrected visibility of 29%, in quantitative agreement with the pure dephasing of the individual sources. Due to its efficient photon extraction within a broad spectral range (>20 nm), our microlens-based approach is predestinated for future entanglement swapping experiments utilizing entangled photon pairs emitted by distant biexciton-exciton radiative cascades.DFG, 43659573, SFB 787: Halbleiter - Nanophotonik: Materialien, Modelle, BauelementeEC/FP7/615613/EU/External Quantum Control of Photonic Semiconductor Nanostructures/EXQUISIT
In situ electron-beam lithography of deterministic single-quantum-dot mesa-structures using low-temperature cathodoluminescence spectroscopy
No full textThis content may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This material originally appeared in Appl. Phys. Lett. 102, 251113 (2013) and may be found at https://doi.org/10.1063/1.4812343.We report on the deterministic fabrication of sub-μm mesa-structures containing single quantum dots (QDs) by in situ electron-beam lithography. The fabrication method is based on a two-step lithography process: After detecting the position and spectral features of single InGaAs QDs by cathodoluminescence (CL) spectroscopy, circular sub-μm mesa-structures are defined by high-resolution electron-beam lithography and subsequent etching. Micro-photoluminescence spectroscopy demonstrates the high optical quality of the single-QD mesa-structures with emission linewidths below 15 μeV and g(2)(0) = 0.04. Our lithography method has an alignment precision better than 100 nm which paves the way for a fully deterministic device technology using in situ CL lithography.DFG, 43659573, SFB 787: Halbleiter - Nanophotonik: Materialien, Modelle, Bauelement
Advanced in-situ electron-beam lithography for deterministic nanophotonic device processing
No full textThis article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Review of Scientific Instruments 86, 073903 (2015) and may be found at https://doi.org/10.1063/1.4926995.We report on an advanced in-situ electron-beam lithography technique based on high-resolution cathodoluminescence (CL) spectroscopy at low temperatures. The technique has been developed for the deterministic fabrication and quantitative evaluation of nanophotonic structures. It is of particular interest for the realization and optimization of non-classical light sources which require the pre-selection of single quantum dots (QDs) with very specific emission features. The two-step electron-beam lithography process comprises (a) the detailed optical study and selection of target QDs by means of CL-spectroscopy and (b) the precise retrieval of the locations and integration of target QDs into lithographically defined nanostructures. Our technology platform allows for a detailed pre-process determination of important optical and quantum optical properties of the QDs, such as the emission energies of excitonic complexes, the excitonic fine-structure splitting, the carrier dynamics, and the quantum nature of emission. In addition, it enables a direct and precise comparison of the optical properties of a single QD before and after integration which is very beneficial for the quantitative evaluation of cavity-enhanced quantum devices.DFG, 43659573, SFB 787: Halbleiter - Nanophotonik: Materialien, Modelle, Bauelement
