Spatio-temporal coherence in vertically emitting GaAs-based electrically driven polariton lasers

Authors gratefully acknowledge the financial support by the state of Bavaria, the DFG within the projects Schn1376-3.1 as well as KL3124/2-1 and the Wurzburg-Dresden Cluster of Excellence on Complexity and Topology in Quantum Matter - ct.qmat. S.H. is grateful for funding received within the EPSRC Hybrid Polaritonics programme grant (EP/M025330/1).We report on the implementation of a GaAs-based, vertically emitting electrically pumped polariton laser operated at cryogenic temperatures. The structure consists of a high quality factor AlGaAs/AlAs microcavity (Q=15 000) with two stacks of four GaAs quantum wells and features a Rabi splitting of 11 meV. Polariton lasing manifests by a clear threshold in the input–output characteristics of our device with a sharp drop in the emission linewidth and a continuous blueshift of 0.7 meV above threshold with increasing injection current. We measure spatial and temporal coherence of our device in the condensed phase by utilizing interference spectroscopy. Our results clearly demonstrate that electrically driven polariton lasers have promise as monolithic polaritonic sources of coherent light.PostprintPeer reviewe

Direct SIMS Determination of the InxGa1-xN Mole Fraction

We demonstrate that our secondary mass ion spectroscopy (SIMS) method for the determination of the mole fraction in solid InxGa1-xN solutions is accurate and reproduceable without need of reference samples. The method is based on measuring relative current values of CsM+ (M=Ga, In) secondary ions. The claim of reliable SIMS determination without reference samples was confirmed by four independent analytical methods on the same samples with a relative error in the InN mole fraction determination below 15

A hypothalamic-thalamostriatal circuit that controls approach-avoidance conflict in rats

Survival depends on a balance between seeking rewards and avoiding potential threats, but the neural circuits that regulate this motivational conflict remain largely unknown. Using an approach-food vs. avoid-predator threat conflict test in rats, we identified a subpopulation of neurons in the anterior portion of the paraventricular thalamic nucleus (aPVT) which express corticotrophin-releasing factor (CRF) and are preferentially recruited during conflict. Inactivation of aPVTCRF neurons during conflict biases animal’s response toward food, whereas activation of these cells recapitulates the food-seeking suppression observed during conflict. aPVTCRF neurons project densely to the nucleus accumbens (NAc), and activity in this pathway reduces food seeking and increases avoidance. In addition, we identified the ventromedial hypothalamus (VMH) as a critical input to aPVTCRF neurons, and demonstrated that VMH-aPVT neurons mediate defensive behaviors exclusively during conflict. Together, our findings describe a hypothalamic-thalamostriatal circuit that suppresses reward-seeking behavior under the competing demands of avoiding threats.Fil: Engelke, D. S.. The University of Texas Health Science Center; Estados UnidosFil: Zhang, X. O.. The University of Texas Health Science Center; Estados UnidosFil: O’Malley, J. J.. The University of Texas Health Science Center; Estados UnidosFil: Fernandez Leon, Jose Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. Sede Olavarría del Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aire. Universidad Nacional del Centro de la Provincia de Buenos Aires. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. Sede Olavarría del Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; ArgentinaFil: Li, S.. University of Manitoba; CanadáFil: Kirouac, G. J.. University of Manitoba; CanadáFil: Beierlein, M.. The University of Texas Health Science Center; Estados UnidosFil: Do Monte, F. H.. The University of Texas Health Science Center; Estados Unido

Effects of the linear polarization of polariton condensates in their propagation in codirectional couplers

We report on the linear polarization of polariton condensates in a codirectional coupler that allows evanescent coupling between adjacent waveguides. During the condensate's formation, polaritons usually acquire a randomly oriented polarization, however, our results reveal a preferential orientation of the linear polarization along the waveguide propagation path. Furthermore, we observe polarization-dependent intensity oscillations in the output terminal of the coupler, and we identify the mode beating between the linear-polarized eigenmodes as the origin of these oscillations. Our findings provide an insight into the control of the polarization of polariton condensates, paving the way for the development of spin-based polaritonic architectures where condensates propagate over macroscopic distancesThis work has been partly supported by the Spanish MINECO Grant Nos. MAT2017-83722-R and PID2020-113445GB-I00. A.Y. and I.A.S. were financially supported by the Ministry of Science and Higher Education of the Russian Federation through Megagrant Number 14.Y26.31.0015 and Goszadanie No. 2019-1246. I.A.S. acknowledges also the support from theIcelandic research fund, Grant No. 163082-051. The Würzburgand Jena group acknowledges financial support within the DFGProject Nos. PE 523/18-1 and KL3124/2-1. The Würzburggroup acknowledges financial support by the German ResearchFoundation (DFG) under Germany’s Excellence Strategy−EXC2147 “ct.qmat” (Project No. 390858490) and is grateful forsupport by the state of Bavari

Impact of the energetic landscape on polariton condensates’ propagation along a coupler

Funding: This work has been partly supported by the Spanish MINECO Grant No. MAT2017-83722-R. E.R. acknowledges financial support from the FPI Scholarship No. BES-2015-074708. The Würzburg and Jena group acknowledge financial support within the DFG project PE 523/18-1,KL3124/2-1and SCHN1376 3-1. The Würzburg group is grateful for support from the state of Bavaria and within the Würzburg-Dresden Cluster of Excellence ct.qmat. A.Y.and I.A.S. thank the Russian Science Foundation for financial support, Project No. 18-72-10110.Polariton condensates' propagation is strongly dependent on the particular energy landscape the particles are moving upon, in which the geometry of the pathway laid for their movement plays a crucial role. Bends in the circuit's trajectories affect the condensates' speed and oblique geometries introduce an additional discretization of the polaritons' momenta due to the mixing of short and long axis wavevectors on the propagating eigenvalues. In this work, the nature of the propagation of condensates along the arms of a polariton coupler is studied by a combination of time‐resolved micro‐tomography measurements and a theoretical model based on a mean field approximation where condensed polaritons are described by an equation for the slow varying amplitude of the polariton field coupled to an equation for the density of incoherent excitons.Publisher PDFPeer reviewe

Software environment for controlling and re-configuration of Xilinx Virtex FPGAs – TWEPP-07

The Time Projection Chamber is one of the detectors of the ALICE experiment, that is currently being commissioned at the Large Hadron Collider at CERN. The Detector Control System is used for control and monitoring of the system. For the TPC Front-End Electronics (FEE) the control node is a Readout Control Unit that communicates to higher layers via Ethernet, using the standard framework DIM. The Readout Control Unit is equipped with commercial SRAM based FPGAs that will experience errors due to the radiation environment they are operating in. This article will present the implemented hardware solution for error correction and will focus on the software environment for configuration and controlling of the system – TWEPP-07

Braneworld effective action and origin of inflation

We construct braneworld effective action in two brane Randall-Sundrum model and show that the radion mode plays the role of a scalar field localizing essentially nonlocal part of this action. Non-minimal curvature coupling of this field reflects the violation of AdS/CFT-correspondence for finite values of brane separation. Under small detuning of the brane tension from the Randall-Sundrum flat brane value, the radion mode can play the role of inflaton. Inflationary dynamics corresponds to branes moving apart in the field of repelling interbrane inflaton-radion potential and implies the existence acceleration stage caused by remnant cosmological constant at late (large brane separation) stages of evolution. We discuss the possibility of fixing initial conditions in this model within the concept of braneworld creation from the tunneling or no-boundary cosmological state, which formally replaces the conventional moduli stabilization mechanism.Comment: 18 pages, LaTeX, the effective action form factor is corrected for small separation between branes and new references are adde

Polariton condensation in S- and P-flatbands in a two-dimensional Lieb lattice

S.K. acknowledges the European Commission for the H2020 Marie Sklodowska-Curie Actions (MSCA) fellowship (Topopolis). The Wurzburg group acknowledges the financial support by the state of Bavaria and the Deutsche Forschungsgemeinschaft (DFG) within the project Schn1376-3.1.We study the condensation of exciton-polaritons in a two-dimensional Lieb lattice of micropillars. We show selective polariton condensation into the flatbands formed by S and Px,y orbital modes of the micropillars under non-resonant laser excitation.The real space mode patterns of these condensates are accurately reproduced bythe calculation of related Bloch modes of S- and P-flatbands. Our work emphasizes the potential of exciton-polariton lattices to emulate Hamiltonians of advanced potential landscapes. Furthermore, the obtained results provide a deeper inside into the physics of flatbands known mostly within the tight-binding limit.PostprintPostprintPeer reviewe

Counter-directional polariton coupler

The Wurzburg group acknowledges the financial support by the state of Bavaria and the DFG within the project Schn1376-3.1. J.B. and S.K. acknowledge funding from DFG grant KL3124/2-1. The Madrid team acknowledges financial support by the Spanish MINECO Grants MAT2014-53119-C2-1-R and MAT2017-83722-R.We report on an on-chip routing device for propagating condensates of exciton-polaritons. This counter-directional coupler implements signal control by a photonic microdisk potential, which couples two lithographically defined waveguides and reverses the condensate's propagation direction. By varying the structural sizes, we utilize the conjunction of the different dimensionalities to additionally evidence the functionality of a polaritonic resonant tunnel diode. Furthermore, we show the ultra fast time dynamics of the device via ps-resolved streak camera measurements. This scalable, all-directional coupler element is a central building block for compact non-linear on-chip photonic architectures.PostprintPeer reviewe