Sideband pump-probe technique resolves nonlinear modulation response of PbS/CdS quantum dots on a silicon nitride waveguide

For possible applications of colloidal nanocrystals in optoelectronics and nanophotonics, it is of high interest to study their response at low excitation intensity with high repetition rates, as switching energies in the pJ/bit to sub-pJ/bit range are targeted. We develop a sensitive pump-probe method to study the carrier dynamics in colloidal PbS/CdS quantum dots deposited on a silicon nitride waveguide after excitation by laser pulses with an average energy of few pJ/pulse. We combine an amplitude modulation of the pump pulse with phase-sensitive heterodyne detection. This approach permits to use co-linearly propagating co-polarized pulses. The method allows resolving transmission changes of the order of 10(-5) and phase changes of arcseconds. We find a modulation on a sub-nanosecond time scale caused by Auger processes and biexciton decay in the quantum dots. With ground state lifetimes exceeding 1 mu s, these processes become important for possible realizations of opto-electronic switching and modulation based on colloidal quantum dots emitting in the telecommunication wavelength regime

Strong amplitude-phase coupling in submonolayer quantum dots

This 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. 109, 201102 (2016) and may be found at https://doi.org/10.1063/1.4967833.Submonolayer quantum dots promise to combine the beneficial features of zero- and two-dimensional carrier confinement. To explore their potential with respect to all-optical signal processing, we investigate the amplitude-phase coupling (α-parameter) in semiconductor optical amplifiers based on InAs/GaAs submonolayer quantum dots in ultrafast pump-probe experiments. Lateral coupling provides an efficient carrier reservoir and gives rise to a large α-parameter. Combined with a high modal gain and an ultrafast gain recovery, this makes the submonolayer quantum dots an attractive gain medium for nonlinear optical signal processing

Social Dominance Orientation Connects Prejudicial Human-Human and Human-Animal Relations

Recent theorizing suggests that biases toward human outgroups may be related to biases toward (non-human) animals, and that individual differences in desire for group dominance and inequality may underlie associations between these biases. The present investigation directly tests these assumptions. As expected, the results of the current study (N = 191) demonstrate that endorsing speciesist attitudes is significantly and positively associated with negative attitudes toward ethnic outgroups. Importantly, individual differences in social dominance orientation accounted for the association between speciesist and ethnic outgroup attitudes; that is, these variables are associated due to their common association with social dominance orientation that underpins these biases. We conclude that social dominance orientation represents a critical individual difference variable underlying ideological belief systems and attitudes pertaining to both human-human intergroup and human-animal relations

Calcineurin signaling promotes Takotsubo syndrome

Acknowledgements We thank P. Nawroth (Department of Endocrinology, University Hospital Heidelberg, Germany) for the opportunity to conduct RIA (corticosterone), HPLC (catecholamines) and automated Cobas (hs-TnT) analysis in his laboratory. S. Martinache (Department of General Internal Medicine and Psychosomatics, University Hospital Heidelberg, Germany), J. Krebs-Haupenthal, S. Harrack and M. Oestringer (all affiliated with the Institute of Experimental Cardiology, Medical Faculty, Heidelberg University, Germany) provided excellent technical assistance. This work was supported by grants from the Deutsche Forschungsgemeinschaft (BA 2258/9-1 and the CRC 1550, INST 35/1699-1) and the Deutsches Zentrum für Herz-Kreislauf-Forschung (DZHK; German Centre for Cardiovascular Research), from the BMBF (German Ministry of Education and Research) to J.B., from the German Cardiac Society (DGK) to B.B., I.B. and M.S., and from the German Heart Foundation (DHS) to M.A. C.D. and N.F. were also supported by the CRC 1550 and DZHK. The funders had no role in study design, data collection and analysis, the decision to publish or preparation of the manuscript.Peer reviewedPublisher PD

Gain dynamics of quantum dot devices for dual-state operation

This 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. 104, 261108 (2014) and may be found at https://doi.org/10.1063/1.4885383.Ground state gain dynamics of In(Ga)As-quantum dot excited state lasers are investigated via single-color ultrafast pump-probe spectroscopy below and above lasing threshold. Two-color pump-probe experiments are used to localize lasing and non-lasing quantum dots within the inhomogeneously broadened ground state. Single-color results yield similar gain recovery rates of the ground state for lasing and non-lasing quantum dots decreasing from 6 ps to 2 ps with increasing injection current. We find that ground state gain dynamics are influenced solely by the injection current and unaffected by laser operation of the excited state. This independence is promising for dual-state operation schemes in quantum dot based optoelectronic devices.DFG, 43659573, SFB 787: Halbleiter - Nanophotonik: Materialien, Modelle, Bauelement

Fast gain and phase recovery of semiconductor optical amplifiers based on submonolayer quantum dots

This 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. 107, 201102 (2015) and may be found at https://doi.org/10.1063/1.4935792.Submonolayer quantum dots as active medium in opto-electronic devices promise to combine the high density of states of quantum wells with the fast recovery dynamics of self-assembled quantum dots. We investigate the gain and phase recovery dynamics of a semiconductor optical amplifier based on InAs submonolayer quantum dots in the regime of linear operation by one- and two-color heterodyne pump-probe spectroscopy. We find an as fast recovery dynamics as for quantum dot-in-a-well structures, reaching 2 ps at moderate injection currents. The effective quantum well embedding the submonolayer quantum dots acts as a fast and efficient carrier reservoir.DFG, 43659573, SFB 787: Halbleiter - Nanophotonik: Materialien, Modelle, BauelementeDFG, 87159868, GRK 1558: Kollektive Dynamik im Nichtgleichgewicht: in kondensierter Materie und biologischen Systeme