Universität Stuttgart
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Item Open Access Towards fiber-coupled plasmonic perfect absorber superconducting nanowire photodetectors for the near- and mid-infrared(2023) Mennle, Sandra; Karl, Philipp; Ubl, Monika; Ruchka, Pavel; Weber, Ksenia; Hentschel, Mario; Flad, Philipp; Giessen, HaraldItem Open Access Integrated optoelectronic devices using lab‐on‐fiber technology(2022) Ricciardi, Armando; Zimmer, Michael; Witz, Norbert; Micco, Alberto; Piccirillo, Federica; Giaquinto, Martino; Kaschel, Mathias; Burghartz, Joachim; Jetter, Michael; Michler, Peter; Cusano, Andrea; Portalupi, Simone LucaSilica fibers are nowadays cornerstones in several technological implementations from long‐distance communication, to sensing applications in many scenarios. To further enlarge the functionalities, the compactness, and the performances of fiber‐based devices, one needs to reliably integrate small‐footprint components such as sensors, light sources, and detectors onto single optical fiber substrates. Here, a novel proof of concept is presented to deterministically integrate optoelectronic chips onto the facet of an optical fiber, further implementing the electrical contacting between the chip and fiber itself. The CMOS‐compatible procedure is based on a suitable combination of metal deposition, laser machining, and micromanipulation, directly applied onto the fiber tip. The proposed method is validated by transferring, aligning, and bonding a quantum‐well based laser on the core of a multimode optical fiber. The successful monolithic device integration on fiber shows simultaneously electrical contacting between the laser and the ferrule, and 20% light in‐coupling in the fiber. These results pave new ways to develop the next generation of optoelectronic systems on fiber. The technological approach will set a new relevant milestone along the lab‐on‐fiber roadmap, opening new avenues for a novel class of integrated optoelectronic fiber platforms, featuring unrivaled miniaturization, compactness, and performances levels, designed for specific applications.Item Open Access 3D printed micro-optics for quantum technology: Optimised coupling of single quantum dot emission into a single-mode fibre(2021) Sartison, Marc; Weber, Ksenia; Thiele, Simon; Bremer, Lucas; Fischbach, Sarah; Herzog, Thomas; Kolatschek, Sascha; Jetter, Michael; Reitzenstein, Stephan; Herkommer, Alois; Michler, Peter; Portalupi, Simone Luca; Giessen, HaraldItem Open Access Quantum nonlinear spectroscopy of single nuclear spins(2022) Meinel, Jonas; Vorobyov, Vadim; Wang, Ping; Yavkin, Boris; Pfender, Mathias; Sumiya, Hitoshi; Onoda, Shinobu; Isoya, Junichi; Liu, Ren-Bao; Wrachtrup, JörgConventional nonlinear spectroscopy, which use classical probes, can only access a limited set of correlations in a quantum system. Here we demonstrate that quantum nonlinear spectroscopy, in which a quantum sensor and a quantum object are first entangled and the sensor is measured along a chosen basis, can extract arbitrary types and orders of correlations in a quantum system. We measured fourth-order correlations of single nuclear spins that cannot be measured in conventional nonlinear spectroscopy, using sequential weak measurement via a nitrogen-vacancy center in diamond. The quantum nonlinear spectroscopy provides fingerprint features to identify different types of objects, such as Gaussian noises, random-phased AC fields, and quantum spins, which would be indistinguishable in second-order correlations. This work constitutes an initial step toward the application of higher-order correlations to quantum sensing, to examining the quantum foundation (by, e.g., higher-order Leggett-Garg inequality), and to studying quantum many-body physics.Item Open Access Electro-active metaobjective from metalenses-on-demand(2022) Karst, Julian; Lee, Yohan; Floess, Moritz; Ubl, Monika; Ludwigs, Sabine; Hentschel, Mario; Giessen, HaraldSwitchable metasurfaces can actively control the functionality of integrated metadevices with high efficiency and on ultra-small length scales. Such metadevices include active lenses, dynamic diffractive optical elements, or switchable holograms. Especially, for applications in emerging technologies such as AR (augmented reality) and VR (virtual reality) devices, sophisticated metaoptics with unique functionalities are crucially important. In particular, metaoptics which can be switched electrically on or off will allow to change the routing, focusing, or functionality in general of miniaturized optical components on demand. Here, we demonstrate metalenses-on-demand made from metallic polymer plasmonic nanoantennas which are electrically switchable at CMOS (complementary metal-oxide-semiconductor) compatible voltages of ±1 V. The nanoantennas exhibit plasmonic resonances which can be reversibly switched ON and OFF via the applied voltage, utilizing the optical metal-to-insulator transition of the metallic polymer. Ultimately, we realize an electro-active non-volatile multi-functional metaobjective composed of two metalenses, whose unique optical states can be set on demand. Overall, our work opens up the possibility for a new level of electro-optical elements for ultra-compact photonic integration.Item Open Access Extending quantum links : modules for fiber‐ and memory‐based quantum repeaters(2020) Loock, Peter van; Alt, Wolfgang; Becher, Christoph; Benson, Oliver; Boche, Holger; Deppe, Christian; Eschner, Jürgen; Höfling, Sven; Meschede, Dieter; Michler, Peter; Schmidt, Frank; Weinfurter, HaraldElementary building blocks for quantum repeaters based on fiber channels and memory stations are analyzed. Implementations are considered for three different physical platforms, for which suitable components are available: quantum dots, trapped atoms and ions, and color centers in diamond. The performances of basic quantum repeater links for these platforms are evaluated and compared, both for present‐day, state‐of‐the‐art experimental parameters as well as for parameters that can in principle be reached in the future. The ultimate goal is to experimentally explore regimes at intermediate distances - up to a few 100 km - in which the repeater‐assisted secret key transmission rates exceed the maximal rate achievable via direct transmission. Two different protocols are considered, one of which is better adapted to the higher source clock rate and lower memory coherence time of the quantum dot platform, while the other circumvents the need of writing photonic quantum states into the memories in a heralded, nondestructive fashion. The elementary building blocks and protocols can be connected in a modular form to construct a quantum repeater system that is potentially scalable to large distances.Item Open Access Nanoscale mapping of magnetic auto-oscillations with a single spin sensor(2025) Hache, Toni; Anshu, Anshu; Shalomayeva, Tetyana; Richter, Gunther; Stöhr, Rainer; Kern, Klaus; Wrachtrup, Jörg; Singha, AparajitaSpin Hall nano-oscillators convert DC to magnetic auto-oscillations in the microwave regime. Current research on these devices is dedicated to creating next-generation energy-efficient hardware for communication technologies. Despite intensive research on magnetic auto-oscillations within the past decade, the nanoscale mapping of those dynamics remained a challenge. We image the distribution of free-running magnetic auto-oscillations by driving the electron spin resonance transition of a single spin quantum sensor, enabling fast acquisition (100 ms/pixel). With quantitative magnetometry, we experimentally demonstrate for the first time that the auto-oscillation spots are localized at magnetic field minima acting as local potential wells for confining spin-waves. By comparing the magnitudes of the magnetic stray field at these spots, we decipher the different frequencies of the auto-oscillation modes. The insights gained regarding the interaction between auto-oscillation modes and spin-wave potential wells enable advanced engineering of real devices.Item Open Access Optical charge injection and coherent control of a quantum-dot spin-qubit emitting at telecom wavelengths(2022) Dusanowski, Łukasz; Nawrath, Cornelius; Portalupi, Simone L.; Jetter, Michael; Huber, Tobias; Klembt, Sebastian; Michler, Peter; Höfling, SvenSolid-state quantum emitters with manipulable spin-qubits are promising platforms for quantum communication applications. Although such light-matter interfaces could be realized in many systems only a few allow for light emission in the telecom bands necessary for long-distance quantum networks. Here, we propose and implement an optically active solid-state spin-qubit based on a hole confined in a single InAs/GaAs quantum dot grown on an InGaAs metamorphic buffer layer emitting photons in the C-band. We lift the hole spin-degeneracy using an external magnetic field and demonstrate hole injection, initialization, read-out and complete coherent control using picosecond optical pulses. These results showcase a solid-state spin-qubit platform compatible with preexisting optical fiber networks.Item Open Access Momentum space separation of quantum path interferences between photons and surface plasmon polaritons in nonlinear photoemission microscopy(2024) Dreher, Pascal; Janoschka, David; Giessen, Harald; Schützhold, Ralf; Davis, Timothy J.; Horn-von Hoegen, Michael; Meyer zu Heringdorf, Frank-JoachimQuantum path interferences occur whenever multiple equivalent and coherent transitions result in a common final state. Such interferences strongly modify the probability of a particle to be found in that final state, a key concept of quantum coherent control. When multiple nonlinear and energy-degenerate transitions occur in a system, the multitude of possible quantum path interferences is hard to disentangle experimentally. Here, we analyze quantum path interferences during the nonlinear emission of electrons from hybrid plasmonic and photonic fields using time-resolved photoemission electron microscopy. We experimentally distinguish quantum path interferences by exploiting the momentum difference between photons and plasmons and through balancing the relative contributions of their respective fields. Our work provides a fundamental understanding of the nonlinear photon-plasmon-electron interaction. Distinguishing emission processes in momentum space, as introduced here, could allow nano-optical quantum-correlations to be studied without destroying the quantum path interferences.Item Open Access Quantitative determination of the electric field strength in a plasmon focus from ponderomotive energy shifts(2022) Dreher, Pascal; Janoschka, David; Neuhaus, Alexander; Frank, Bettina; Giessen, Harald; Horn-von Hoegen, Michael; Meyer zu Heringdorf, Frank-JoachimSpectroscopic photoemission microscopy is used to detect and quantify a ponderomotive shift in the energy of electrons that are emitted from a surface plasmon polariton focus. The focus is formed on an atomically flat Au(111) surface by an Archimedean spiral and is spatiotemporally separated from the circularly polarized light pulse used to excite the spiral. A spectroscopic analysis of electrons emitted from the focus exhibits a peaked above-threshold electron emission spectrum. From the shift of the peaks as function of laser power the field strength of the surface plasmon polariton was quantitatively determined without free parameters. Estimations of the Keldysh parameter γ = 4.4 and the adiabaticity parameter δ = 4700 indicate that electron emission occurs in a regime of multiplasmon absorption and nonlocalized surface plasmon fields.