Showing papers by "Sven Höfling published in 2021"
TL;DR: The findings unveil a future route for topological defect engineering and tuning in non-Hermitian systems of arbitrary dimension and resolve not only topological edge states, but also a novel PT-symmetric Z_{2} invariant of the bulk.
Abstract: We employ electric circuit networks to study topological states of matter in non-Hermitian systems enriched by parity-time symmetry PT and chiral symmetry anti-PT (APT). The topological structure manifests itself in the complex admittance bands which yields excellent measurability and signal to noise ratio. We analyze the impact of PT-symmetric gain and loss on localized edge and defect states in a non-Hermitian Su-Schrieffer-Heeger (SSH) circuit. We realize all three symmetry phases of the system, including the APT-symmetric regime that occurs at large gain and loss. We measure the admittance spectrum and eigenstates for arbitrary boundary conditions, which allows us to resolve not only topological edge states, but also a novel PT-symmetric Z_{2} invariant of the bulk. We discover the distinct properties of topological edge states and defect states in the phase diagram. In the regime that is not PT symmetric, the topological defect state disappears and only reemerges when APT symmetry is reached, while the topological edge states always prevail and only experience a shift in eigenvalue. Our findings unveil a future route for topological defect engineering and tuning in non-Hermitian systems of arbitrary dimension.
90 citations
TL;DR: In this paper, the authors demonstrate that topological insulator laser arrays are arrays of semiconductor lasers that exploit fundamental features of topology to force all emitters to act as a single coherent laser.
Abstract: Topological insulator lasers are arrays of semiconductor lasers that exploit fundamental features of topology to force all emitters to act as a single coherent laser. In this study, we demonstrate ...
55 citations
TL;DR: In this paper, a coherent condensate of exciton-polaritons, extending spatially up to 4'µm and spinpolarizable with an external magnetic field, is observed at cryogenic temperatures in a MoSe2 monolayer embedded in a vertical microcavity.
Abstract: The emergence of two-dimensional crystals has revolutionized modern solid-state physics. From a fundamental point of view, the enhancement of charge carrier correlations has sparked much research activity in the transport and quantum optics communities. One of the most intriguing effects, in this regard, is the bosonic condensation and spontaneous coherence of many-particle complexes. Here we find compelling evidence of bosonic condensation of exciton–polaritons emerging from an atomically thin crystal of MoSe2 embedded in a dielectric microcavity under optical pumping at cryogenic temperatures. The formation of the condensate manifests itself in a sudden increase of luminescence intensity in a threshold-like manner, and a notable spin-polarizability in an externally applied magnetic field. Spatial coherence is mapped out via highly resolved real-space interferometry, revealing a spatially extended condensate. Our device represents a decisive step towards the implementation of coherent light-sources based on atomically thin crystals, as well as non-linear, valleytronic coherent devices. A coherent condensate of exciton–polaritons, extending spatially up to 4 µm and spin-polarizable with an external magnetic field, is observed at cryogenic temperatures in a MoSe2 monolayer embedded in a vertical microcavity.
42 citations
TL;DR: Results demonstrate that unconventional excitons in MoSe_{2} are highly favorable for the implementation of large exciton-mediated optical nonlinearities, potentially working up to room temperature.
Abstract: In transition metal dichalcogenides' layers of atomic-scale thickness, the electron-hole Coulomb interaction potential is strongly influenced by the sharp discontinuity of the dielectric function across the layer plane This feature results in peculiar nonhydrogenic excitonic states in which exciton-mediated optical nonlinearities are predicted to be enhanced compared to their hydrogenic counterparts To demonstrate this enhancement, we perform optical transmission spectroscopy of a ${\mathrm{MoSe}}_{2}$ monolayer placed in the strong coupling regime with the mode of an optical microcavity and analyze the results quantitatively with a nonlinear input-output theory We find an enhancement of both the exciton-exciton interaction and of the excitonic fermionic saturation with respect to realistic values expected in the hydrogenic picture Such results demonstrate that unconventional excitons in ${\mathrm{MoSe}}_{2}$ are highly favorable for the implementation of large exciton-mediated optical nonlinearities, potentially working up to room temperature
30 citations
TL;DR: In this paper, a slightly biased pristine bilayer was shown to have strongly dipolar excitons, which preserve a strong oscillator strength, and they scrutinized their giant dipole moment and shed further light on their orbital and valley physics via bias-dependent magnetic field measurements.
Abstract: van der Waals heterostructures composed of transition metal dichalcogenide monolayers (TMDCs) are characterized by their truly rich excitonic properties which are determined by their structural, geometric, and electronic properties: In contrast to pure monolayers, electrons and holes can be hosted in different materials, resulting in highly tunable dipolar many-particle complexes. However, for genuine spatially indirect excitons, the dipolar nature is usually accompanied by a notable quenching of the exciton oscillator strength. Via electric and magnetic field dependent measurements, we demonstrate that a slightly biased pristine bilayer ${\mathrm{MoS}}_{2}$ hosts strongly dipolar excitons, which preserve a strong oscillator strength. We scrutinize their giant dipole moment, and shed further light on their orbital and valley physics via bias-dependent magnetic field measurements.
28 citations
TL;DR: In this article, a deterministic Purcell-enhanced single photon source is realized by integrating an atomically thin WSe2 layer with a circular Bragg grating cavity, which significantly enhances the photoluminescence from the thin layer and supports single photon generation with g(2)(0) < 0.25.
Abstract: We demonstrate a deterministic Purcell-enhanced single photon source realized by integrating an atomically thin WSe2 layer with a circular Bragg grating cavity. The cavity significantly enhances the photoluminescence from the atomically thin layer and supports single photon generation with g(2)(0) < 0.25. We observe a consistent increase of the spontaneous emission rate for WSe2 emitters located in the center of the Bragg grating cavity. These WSe2 emitters are self-aligned and deterministically coupled to such a broadband cavity, configuring a new generation of deterministic single photon sources, characterized by their simple and low-cost production and intrinsic scalability.
22 citations
TL;DR: In this article, topological concepts have been applied to a wide range of fields in order to successfully describe the emergence of robust edge modes that are unaffected by scattering or disorder in photonics.
Abstract: Topological concepts have been applied to a wide range of fields in order to successfully describe the emergence of robust edge modes that are unaffected by scattering or disorder. In photonics, in...
21 citations
TL;DR: In this article, a patterned mirror cavity was used to tune the lattice potential landscape of a linear Su-Schrieffer-Heeger chain to design topological defects at domain boundaries and at the edge.
Abstract: Interacting bosonic particles in artificial lattices have proven to be a powerful tool for the investigation of exotic phases of matter as well as phenomena resulting from nontrivial topology. Exciton-polaritons, bosonic quasi-particles of light and matter, have been shown to combine the on-chip benefits of optical systems with strong interactions, inherited from their matter character. Technologically significant semiconductor platforms strictly require cryogenic temperatures. In this communication, we demonstrate exciton-polariton lasing for topological defects emerging from the imprinted lattice structure at room temperature. We utilize red fluorescent protein derived from DsRed of Discosoma sea anemones, hosting highly stable Frenkel excitons. Using a patterned mirror cavity, we tune the lattice potential landscape of a linear Su-Schrieffer-Heeger chain to design topological defects at domain boundaries and at the edge. We unequivocally demonstrate polariton lasing from these topological defects. This progress has paved the road to interacting boson many-body physics under ambient conditions.
18 citations
TL;DR: In this paper, the authors show that the interaction between microcavity photons and excitons in an atomically thin WSe2 results in a hybridized regime of strong light-matter coupling.
Abstract: The emergence of spatial and temporal coherence of light emitted from solid-state systems is a fundamental phenomenon intrinsically aligned with the control of light-matter coupling. It is canonical for laser oscillation, emerges in the superradiance of collective emitters, and has been investigated in bosonic condensates of thermalized light, as well as exciton-polaritons. Our room temperature experiments show the strong light-matter coupling between microcavity photons and excitons in atomically thin WSe2. We evidence the density-dependent expansion of spatial and temporal coherence of the emitted light from the spatially confined system ground-state, which is accompanied by a threshold-like response of the emitted light intensity. Additionally, valley-physics is manifested in the presence of an external magnetic field, which allows us to manipulate K and K’ polaritons via the valley-Zeeman-effect. Our findings validate the potential of atomically thin crystals as versatile components of coherent light-sources, and in valleytronic applications at room temperature. Here, the authors show that the interaction between microcavity photons and excitons in an atomically thin WSe2 results in a hybridized regime of strong light-matter coupling. Coherence build-up is accompanied by a threshold-like behaviour of the emitted light intensity, which is a fingerprint of a polariton laser effect.
18 citations
TL;DR: In this paper, the authors demonstrate lattice polaritons, based on an open, high-quality optical cavity, with an imprinted photonic lattice strongly coupled to excitons in a WS2 monolayer.
Abstract: Engineering non-linear hybrid light-matter states in tailored lattices is a central research strategy for the simulation of complex Hamiltonians. Excitons in atomically thin crystals are an ideal active medium for such purposes, since they couple strongly with light and bear the potential to harness giant non-linearities and interactions while presenting a simple sample-processing and room temperature operability. We demonstrate lattice polaritons, based on an open, high-quality optical cavity, with an imprinted photonic lattice strongly coupled to excitons in a WS2 monolayer. We experimentally observe the emergence of the canonical band-structure of particles in a one-dimensional lattice at room temperature, and demonstrate frequency reconfigurability over a spectral window exceeding 85 meV, as well as the systematic variation of the nearest-neighbour coupling, reflected by a tunability in the bandwidth of the p-band polaritons by 7 meV. The technology presented in this work is a critical demonstration towards reconfigurable photonic emulators operated with non-linear photonic fluids, offering a simple experimental implementation and working at ambient conditions. Excitons in atomically thin crystals couple strongly with light. Here, the authors observe lattice polaritons in a tunable open optical cavity at room temperature, with an imprinted photonic lattice strongly coupled to excitons in a WS2 monolayer.
16 citations
TL;DR: In this article, a technique to micro-mechanically assemble Fabry-Perot microcavities with high quality Fabry perot micro-materials is presented.
Abstract: Integrating monolayers of two-dimensional semiconductors into optical microcavities is challenging because of the very few available approaches to coat the monolayers with dielectric materials without damaging them. Some strategies have been developed, but they either rely on complicated experimental settings and expensive technologies or limit the achievable cavity quality factors. Thus, high quality Fabry–Perot microcavities are not widely available to the community focusing on light-matter coupling in atomically thin materials. Here, we detail a recently developed technique to micro-mechanically assemble Fabry–Perot microcavities. Our approach promotes strong coupling conditions with excitons in atomically thin materials, it does not rely on difficult or expensive technologies, it is reproducible, and it yields microcavities with quality factors approaching 4000. It is ideally suitable for engineering coupled monolayer-cavity systems of advanced complexity in small-scale laboratories.
TL;DR: By using an on-demand single-photon source based on a semiconductor quantum dot embedded in a micropillar cavity, a heralded controlled-NOT (CNOT) operation between two single photons for the first time is demonstrated.
Abstract: Heralded entangling quantum gates are an essential element for the implementation of large-scale optical quantum computation. Yet, the experimental demonstration of genuine heralded entangling gates with free-flying output photons in linear optical system, was hindered by the intrinsically probabilistic source and double-pair emission in parametric down-conversion. Here, by using an on-demand single-photon source based on a semiconductor quantum dot embedded in a micropillar cavity, we demonstrate a heralded controlled-NOT (CNOT) operation between two single photons for the first time. To characterize the performance of the CNOT gate, we estimate its average quantum gate fidelity of $(87.8\ifmmode\pm\else\textpm\fi{}1.2)%$. As an application, we generated event-ready Bell states with a fidelity of $(83.4\ifmmode\pm\else\textpm\fi{}2.4)%$. Our results are an important step towards the development of photon-photon quantum logic gates.
TL;DR: This work reports on a similar coupling behavior in a controllable, propagative waveguide-based design that is a passive and scalable coupler element that can serve in compact, next generation logic architectures.
Abstract: We report on novel exciton-polariton routing devices created to study and purposely guide light-matter particles in their condensate phase. In a codirectional coupling device, two waveguides are connected by a partially etched section that facilitates tunable coupling of the adjacent channels. This evanescent coupling of the two macroscopic wave functions in each waveguide reveals itself in real space oscillations of the condensate. This Josephson-like oscillation has only been observed in coupled polariton traps so far. Here, we report on a similar coupling behavior in a controllable, propagative waveguide-based design. By controlling the gap width, channel length, or propagation energy, the exit port of the polariton flow can be chosen. This codirectional polariton device is a passive and scalable coupler element that can serve in compact, next generation logic architectures.
TL;DR: In this article, the authors show signatures of a long-sought-after condensed quantum phase, the so-called Bardeen-Cooper-Schrieffer state, in a semiconductor microcavity, laying the foundation for future efficient semiconductor lasers.
Abstract: Experiments show signatures of a long-sought-after condensed quantum phase---the so-called Bardeen-Cooper-Schrieffer state---in a semiconductor microcavity, laying the foundation for future efficient semiconductor lasers.
19 Mar 2021
TL;DR: In this article, the authors apply photon number resolving detectors to explore the photon statistics of bimodal microlasers and show that photon number resolution can be used to explore photon statistics.
Abstract: The authors apply photon number resolving detectors to explore the photon statistics of bimodal microlasers.
TL;DR: The Wurzburg and Jena group acknowledge financial support within the DFG projects PE 523/18-1 and KL 3124/2-1 as mentioned in this paper, and also acknowledge support by the EPSRC “Hybrid Polaritonics” grant (EP/M025330/1).
Abstract: Funding: The Wurzburg and Jena group acknowledge financial support within the DFG projects PE 523/18-1 and KL3124/2-1. The Wurzburg group acknowledges financial support by the German Research Foundation (DFG) under Germany’s Excellence Strategy–EXC2147 “ct.qmat” (project id 390858490). S.H. also acknowledges support by the EPSRC “Hybrid Polaritonics” grant (EP/M025330/1). T.H.H. and S.H. acknowledge funding by the doctoral training program Elitenetzwerk Bayern Graduate School “Topological insulators” (Tols 836315). T.H.H. acknowledges support by the German Academic Scholarship Foundation.
TL;DR: In this article, the authors reported the visibility of quantum interference between two single photons from independent semiconductor quantum-dots (QDs) separated by 302 km optical fiber, which represents a key step to long-distance solid-state quantum networks.
Abstract: In the quest to realize a scalable quantum network, semiconductor quantum
dots (QDs) offer distinct advantages including high single-photon efficiency
and indistinguishability, high repetition rate (tens of GHz with Purcell
enhancement), interconnectivity with spin qubits, and a scalable on-chip
platform. However, in the past two decades, the visibility of quantum
interference between independent QDs rarely went beyond the classical limit of
50$\%$ and the distances were limited from a few meters to kilometers. Here, we
report quantum interference between two single photons from independent QDs
separated by 302 km optical fiber. The single photons are generated from
resonantly driven single QDs deterministically coupled to microcavities.
Quantum frequency conversions are used to eliminate the QD inhomogeneity and
shift the emission wavelength to the telecommunication band. The observed
interference visibility is 0.67$\pm$0.02 (0.93$\pm$0.04) without (with)
temporal filtering. Feasible improvements can further extend the distance to
600 km. Our work represents a key step to long-distance solid-state quantum
networks.
TL;DR: A highly sensitive, selective, and robust tunable laser analyzer that has the capability to analyze several components in a gas sample stream and requires no consumables and no in-field calibration, enabling a low cost of ownership for the analyzer.
Abstract: The detection and measurement of hydrocarbons are of high interest for a variety of applications, for example within the oil and gas industry from extraction throughout the complete refining process, as well as for environmental monitoring and for portable safety devices. This paper presents a highly sensitive, selective, and robust tunable laser analyzer that has the capability to analyze several components in a gas sample stream. More specifically, a multi-gas system for simultaneous detection of C1 to iC5 hydrocarbons, using a room temperature distributed feedback interband cascade laser array, emitting in the 3.3 µm band has been realized. It combines all the advantages of the tunable laser spectroscopy method for a fast, sensitive, and selective in-line multicomponent tunable laser analyzer. Capable of continuous and milliseconds fast monitoring of C1-iC5 hydrocarbon compositions in a process stream, the analyzer requires no consumables (e.g., purging, carrier gas) and no in-field calibration, enabling a low cost of ownership for the analyzer. The system was built based on an industrial GasEye series platform and deployed for the first time in field at Preem refinery in Lysekil, Sweden, in autumn 2018. Results of the measurement campaign and comparison with gas chromatography instrumentation are presented.
TL;DR: In this article, the authors theoretically and experimentally investigate quantum features of an interacting light-matter system from a multidisciplinary perspective, unifying approaches from semiconductor physics, quantum optics, and quantum information science.
Abstract: We theoretically and experimentally investigate quantum features of an interacting light-matter system from a multidisciplinary perspective, unifying approaches from semiconductor physics, quantum optics, and quantum information science. To this end, we quantify the amount of quantum coherence that results from the quantum superposition of Fock states, constituting a measure of the resourcefulness of the produced state for modern quantum protocols. As an archetypal example of a hybrid light-matter interface, we study a polariton condensate and implement a numerical model to predict its properties. Our simulation is confirmed by our proof-of-concept experiment in which we measure and analyze the phase-space distributions of the emitted light. Specifically, we drive a polariton microcavity across the condensation threshold and observe the transition from an incoherent thermal state to a coherent state in the emission, thus confirming the build-up of quantum coherence in the condensate itself.
TL;DR: In this paper, a scalable photonic platform that enables efficient generation of entangled photon pairs from a semiconductor quantum dot is introduced, which is based on a self-aligned quantum dot- micro-cavity structure, erases the need for complex steps of lithography and nanofabrication.
Abstract: We introduce a scalable photonic platform that enables efficient generation of entangled photon pairs from a semiconductor quantum dot. Our system, which is based on a self-aligned quantum dot- micro-cavity structure, erases the need for complex steps of lithography and nanofabrication. We experimentally show collection efficiency of 0.17 combined with a Purcell enhancement of up to 1.7. We harness the potential of our device to generate photon pairs entangled in time bin, reaching a fidelity of 0.84(5) with the maximally entangled state. The achieved pair collection efficiency is 4 times larger than the state-of-the art for this application. The device, which theoretically supports pair extraction efficiencies of nearly 0.5 is a promising candidate for the implementation of bright sources of time-bin, polarization- and hyper entangled photon pairs in a straightforward manner.
TL;DR: In this article, the authors present room temperature memristive switching in a nano-patterned LaAlO3/SrTiO3 wire with laterally defined gates in proximity to the wire.
Abstract: We present room temperature memristive switching in a nano-patterned LaAlO3/SrTiO3 wire with laterally defined gates in proximity to the wire. Closed bias voltage sweeps show pinched hysteresis loops with zero bias resistance values of up to Ron = 8 MΩ and Roff = 1.2 GΩ for the on and off state, respectively. The maximum Roff/Ron ratio is 150. Frequency dependent measurements show a cutoff frequency of around 10 Hz, and the alteration of set point voltages enables us to precisely set and control the resistance off-on ratio. We explain the memristive switching by charge localization on the laterally defined gates, which couple capacitively to the wire and enhance or decrease the resistance dependent on the amount of transferred charges. Our finding enables the realization of geometry-based memristive switching devices, which make use of the form-dependent wire-gate capacitance.
TL;DR: In this article, a process for the fiber-coupling of electrically driven cavity-enhanced quantum dot light emitting devices is described, which allows for the direct and permanent coupling of p-i-n-doped quantum dot micropillar cavities to single-mode optical fibers.
Abstract: We report on a process for the fiber-coupling of electrically driven cavity-enhanced quantum dot light emitting devices. The developed technique allows for the direct and permanent coupling of p-i-n-doped quantum dot micropillar cavities to single-mode optical fibers. The coupling process, fully carried out at room temperature, involves a spatial scanning technique, where the fiber facet is positioned relative to a device with a diameter of 2 μm using the fiber-coupled electroluminescence of the cavity emission as a feedback parameter. Subsequent gluing and UV curing enable a rigid and permanent coupling between micropillar and fiber core. Comparing our experimental results with finite element method simulations indicates a cavity-to-fiber mode-coupling efficiency of ∼46%. Furthermore, we demonstrate pulsed current injection at a repetition rate exceeding 200 MHz as well as low-temperature operation down to 77 K of the fiber-coupled micropillar device. The technique presented in this work is an important step in the quest for efficient and practical quantum light sources for applications in quantum information.
TL;DR: In this article, a deterministic low-index solid immersion lens is placed on top of a single quantum dot in a planar Fabry-Perot microcavity structure, and the structure exhibits an enhancement in the spectral bandwidth to 27nm and a source brightness of 23%.
Abstract: The integration of single quantum dots (QDs) into a planar Fabry–Perot microcavity has been established as a direct and viable approach to vertically steer photons emitted from the quantum emitters, resulting in a strong increase in the source brightness, which becomes particularly evident when a lens with a low numerical aperture is used. However, the spectral bandwidth of QD–microcavity structures is limited and determined by their intrinsic quality factor; these structures are, thus, not ideal for the extraction of entangled photon pairs or for studies of exciton dynamics. We have found that, when a deterministic low-index solid immersion lens is placed on top of the QD in a QD–microcavity structure, the structure exhibits an enhancement in the bandwidth to 27 nm and a source brightness of 23%. The solid immersion lens is deterministically fabricated via two-photon absorption and can be remade several times without perturbing the QD, ensuring that the QD's intrinsic properties are preserved and ensuring its long-term reliability.
TL;DR: In this article, coupled microcavity implementations of Kagome lattices hosting exciton-polariton quantum fluids of light are realized, and the spatial and temporal coherence properties of the laser-like emission from these polariton condensates that are closely connected to the flatband nature of the system are investigated.
Abstract: Kagome lattices supporting Dirac cone and flatband dispersions are well known as a highly frustrated, two-dimensional lattice system. Particularly the flatbands therein are attracting continuous interest based on their link to topological order, correlations and frustration. In this work, we realize coupled microcavity implementations of Kagome lattices hosting exciton-polariton quantum fluids of light. We demonstrate precise control over the dispersiveness of the flatband as well as selective condensation of exciton-polaritons into the flatband. Subsequently, we focus on the spatial and temporal coherence properties of the laser-like emission from these polariton condensates that are closely connected to the flatband nature of the system. Notably, we find a drastic increase in coherence time due to the localization of flatband condensates. Our work illustrates the outstanding suitability of the exciton-polariton system for detailed studies of flatband states as a platform for microlaser arrays in compact localized states, including strong interactions, topology and non-linearity.
TL;DR: In this article, the authors demonstrate single-photon emission with a low probability of multiphoton events of 5% in the C-band of telecommunication spectral range of standard silica fibers from molecular beam epitaxy grown (100)-GaAs-based structure with InAs quantum dots (QDs) on a metamorphic buffer layer.
Abstract: We demonstrate single-photon emission with a low probability of multiphoton events of 5% in the C-band of telecommunication spectral range of standard silica fibers from molecular beam epitaxy grown (100)-GaAs-based structure with InAs quantum dots (QDs) on a metamorphic buffer layer. For this purpose, we propose and implement graded In content digitally alloyed InGaAs metamorphic buffer layer with maximal In content of 42% and GaAs/AlAs distributed Bragg reflector underneath to enhance the extraction efficiency of QD emission. The fundamental limit of the emission rate for the investigated structures is 0.5 GHz based on an emission lifetime of 1.95 ns determined from time-resolved photoluminescence. We prove the relevance of a proposed technology platform for the realization of non-classical light sources in the context of fiber-based quantum communication applications.
05 Mar 2021
TL;DR: In this article, the authors proposed a concept in which a control pulse slows down either the dephasing or the rephasing of the exciton ensembles during its presence.
Abstract: Following the ultrafast optical excitation of an inhomogeneously broadened ensemble, the macroscopic optical polarization decays rapidly due to dephasing. This destructive interference is, however, reversible in photon echo experiments. Here, we propose a concept in which a control pulse slows down either the dephasing or the rephasing of the exciton ensemble during its presence. We analyze and visualize this optical freezing process by showing and discussing results for different single and multiple sequences of control pulses using a simple model of inhomogeneously broadened two-level systems. This idea has been realized in experiments performed on self-assembled (In,Ga)As quantum dots where it was possible to retard or advance the photon echo emission time by several picoseconds. The measurements are in very good agreement with numerical simulations for a more realistic model which, in particular, takes the spatial shape of the laser pulses into account.
TL;DR: In this paper, the authors investigated emission properties of photonic structures with InAs/InGaAlAs/inP quantum dashes grown by molecular beam epitaxy on a distributed Bragg reflector.
Abstract: We investigated emission properties of photonic structures with InAs/InGaAlAs/InP quantum dashes grown by molecular beam epitaxy on a distributed Bragg reflector In high-spatial-resolution photoluminescence experiment, well-resolved sharp spectral lines are observed and single-photon emission is detected in the third telecommunication window characterized by very low multiphoton events probabilities The photoluminescence spectra measured on simple photonic structures in the form of cylindrical mesas reveal significant intensity enhancement by a factor of 4 when compared to a planar sample These results are supported by simulations of the electromagnetic field distribution, which show emission extraction efficiencies even above 18% for optimized designs When combined with relatively simple and undemanding fabrication approach, it makes this kind of structures competitive with the existing solutions in that spectral range and prospective in the context of efficient and practical single-photon sources for fiber-based quantum networks applications
TL;DR: In this paper, gate voltage and temperature dependent transport measurements of InAs/GaSb/InAs triple quantum wells (TQWs) with a designed hybridization gap energy of 4 meV comparable to its traditional double quantum well counterpart are presented.
Abstract: We present gate voltage and temperature dependent transport measurements of InAs/GaSb/InAs triple quantum wells (TQWs) with a designed hybridization gap energy of 4 meV comparable to its traditional double quantum well counterpart. Gate voltage dependent measurements enable us to monitor two electron densities deep in the nonhybridized electron regime and further reveal a clear hybridization gap and a Van Hove singularity in the valence band as a result of the hybridized electron-hole band structure of the TQWs. The evolution of the charge carrier densities and types is studied in detail. Electron and hole densities coexist if the Fermi energy is within the gap and the bottom of the valence band at the \ensuremath{\Gamma} point. On the contrary, only single carrier types can be found far in the conduction and valence band. Thus, we are able to identify the topological band structure of these TQWs. Furthermore, the temperature evolution of the hybridized gap of the triple quantum well is studied. We find a rather temperature insensitive hybridization gap energy.
TL;DR: In this paper, the magneto-transport and magnetoelectroluminescence properties of purely $n$-doped resonant-tunneling diodes with an emitter prewell were investigated.
Abstract: We study the magneto-transport and magnetoelectroluminescence properties of purely $n$-doped ${\mathrm{Ga}\mathrm{As}/\mathrm{Al}}_{0.6}{\mathrm{Ga}}_{0.4}\mathrm{As}$ resonant-tunneling diodes with an ${\mathrm{In}}_{0.15}{\mathrm{Ga}}_{0.85}\mathrm{As}$ quantum well and an emitter prewell. Before the resonant-current condition, magneto-transport measurements reveal charge-carrier densities comparable for diodes with and without the emitter prewell. Landau-level splitting is observed in the electroluminescence emission from the emitter prewell, enabling the determination of the charge-carrier buildup. Our findings show that magnetoelectroluminescence spectroscopy techniques provide useful insights into the charge-carrier dynamics in resonant-tunneling diodes and comprise a versatile tool to complement magneto-transport techniques. This approach might pave the way for the development of potentially more efficient optoelectronic resonant-tunneling devices by, e.g., monitoring voltage-dependent charge accumulation for the improvement of built-in fields and hence the maximization of the photodetector efficiency and/or the minimization of optical losses.