Universität Stuttgart
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Item 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 Modelling and experimental characterization of double layer InP/AlGaInP quantum dot laser(2023) Abbas, Radwa A.; Sabry, Yasser M.; Omran, Haitham; Huang, Zhihua; Zimmer, Michael; Jetter, Michael; Michler, Peter; Khalil, DiaaSpectrum of an InP/AlGaInP self- assembled double-layer quantum dot (QD) laser fabricated by metal-organic vapor-phase epitaxy is theoretically and experimentally investigated. A bimodal QD size distribution (small and large QD groups) was detected which is formed during the fabrication. A model is proposed based on rate equations accounting for the superposition of two inhomogeneous QD groups. The total output power and the power spectral density (PSD) of the fabricated QD laser are experimentally characterized at room temperature. The output spectrum is segmented into the sum of two Gaussians curves (super Gaussian) belonging to the small and large QD groups. The peak PSD and the spectral width of each group are extracted and their dependency on the injected current density is analysed. The peak of the large QDs is found to be dominant at small current while the peak of the small QDs dominated at high current alongside a reduction in its spectral width leading to lasing based on them. This behaviour is attributed to the saturation of the large QDs energy levels due to its relatively long radiative lifetime. The experimental analysis is in a good agreement with the theoretical results.Item Open Access Thin-film InGaAs metamorphic buffer for telecom C-band InAs quantum dots and optical resonators on GaAs platform(2022) Sittig, Robert; Nawrath, Cornelius; Kolatschek, Sascha; Bauer, Stephanie; Schaber, Richard; Huang, Jiasheng; Vijayan, Ponraj; Pruy, Pascal; Portalupi, Simone Luca; Jetter, Michael; Michler, PeterThe GaAs-based material system is well-known for hosting InAs quantum dots (QDs) with outstanding optical properties, typically emitting at a wavelength of around 900 nm. The insertion of a metamorphic buffer (MMB) can shift this emission to the technologically attractive telecom C-band range centered at 1550 nm. However, the thickness of common MMB designs (>1 μm) limits their compatibility with most photonic resonator types. Here, we report on the metal–organic vapor-phase epitaxy (MOVPE) growth of a novel InGaAs MMB with a nonlinear indium content grading profile designed to maximize plastic relaxation within minimal layer thickness. This allows us to achieve the necessary transition of the lattice constant and to provide a smooth surface for QD growth within 180 nm. Single-photon emission at 1550 nm from InAs QDs deposited on top of this thin-film MMB is demonstrated. The strength of the new design is proven by integrating it into a bullseye cavity via nano-structuring techniques. The presented advances in the epitaxial growth of QD/MMB structures form the basis for the fabrication of high-quality telecom nonclassical light sources as a key component of photonic quantum technologies.Item Open Access Observation of ultrafast interfacial Meitner-Auger energy transfer in a Van der Waals heterostructure(2023) Dong, Shuo; Beaulieu, Samuel; Selig, Malte; Rosenzweig, Philipp; Christiansen, Dominik; Pincelli, Tommaso; Dendzik, Maciej; Ziegler, Jonas D.; Maklar, Julian; Xian, R. Patrick; Neef, Alexander; Mohammed, Avaise; Schulz, Armin; Stadler, Mona; Jetter, Michael; Michler, Peter; Taniguchi, Takashi; Watanabe, Kenji; Takagi, Hidenori; Starke, Ulrich; Chernikov, Alexey; Wolf, Martin; Nakamura, Hiro; Knorr, Andreas; Rettig, Laurenz; Ernstorfer, RalphAtomically thin layered van der Waals heterostructures feature exotic and emergent optoelectronic properties. With growing interest in these novel quantum materials, the microscopic understanding of fundamental interfacial coupling mechanisms is of capital importance. Here, using multidimensional photoemission spectroscopy, we provide a layer- and momentum-resolved view on ultrafast interlayer electron and energy transfer in a monolayer-WSe2/graphene heterostructure. Depending on the nature of the optically prepared state, we find the different dominating transfer mechanisms: while electron injection from graphene to WSe2 is observed after photoexcitation of quasi-free hot carriers in the graphene layer, we establish an interfacial Meitner-Auger energy transfer process following the excitation of excitons in WSe2. By analysing the time-energy-momentum distributions of excited-state carriers with a rate-equation model, we distinguish these two types of interfacial dynamics and identify the ultrafast conversion of excitons in WSe2 to valence band transitions in graphene. Microscopic calculations find interfacial dipole-monopole coupling underlying the Meitner-Auger energy transfer to dominate over conventional Förster- and Dexter-type interactions, in agreement with the experimental observations. The energy transfer mechanism revealed here might enable new hot-carrier-based device concepts with van der Waals heterostructures.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 High-rate intercity quantum key distribution with a semiconductor single-photon source(2024) Yang, Jingzhong; Jiang, Zenghui; Benthin, Frederik; Hanel, Joscha; Fandrich, Tom; Joos, Raphael; Bauer, Stephanie; Kolatschek, Sascha; Hreibi, Ali; Rugeramigabo, Eddy Patrick; Jetter, Michael; Portalupi, Simone Luca; Zopf, Michael; Michler, Peter; Kück, Stefan; Ding, FeiQuantum key distribution (QKD) enables the transmission of information that is secure against general attacks by eavesdroppers. The use of on-demand quantum light sources in QKD protocols is expected to help improve security and maximum tolerable loss. Semiconductor quantum dots (QDs) are a promising building block for quantum communication applications because of the deterministic emission of single photons with high brightness and low multiphoton contribution. Here we report on the first intercity QKD experiment using a bright deterministic single photon source. A BB84 protocol based on polarisation encoding is realised using the high-rate single photons in the telecommunication C-band emitted from a semiconductor QD embedded in a circular Bragg grating structure. Utilising the 79 km long link with 25.49 dB loss (equivalent to 130 km for the direct-connected optical fibre) between the German cities of Hannover and Braunschweig, a record-high secret key bits per pulse of 4.8 × 10 -5 with an average quantum bit error ratio of ~ 0.65% are demonstrated. An asymptotic maximum tolerable loss of 28.11 dB is found, corresponding to a length of 144 km of standard telecommunication fibre. Deterministic semiconductor sources therefore challenge state-of-the-art QKD protocols and have the potential to excel in measurement device independent protocols and quantum repeater applications.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 Luca; 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 Surface relief VCSELs at 670 nm with integrated polymer microlens for highly collimated fundamental-mode emission(2024) Engel, Lena; Khamseh, Farnaz; Zimmer, Michael; Jetter, Michael; Michler, PeterItem Open Access Monolithic integration of one VCSEL on a single mode fiber(2025) Piccirillo, Federica; Zimmer, Michael; Giaquinto, Martino; Micco, Alberto; Jetter, Michael; Michler, Peter; Cusano, Andrea; Portalupi, Simone Luca; Ricciardi, ArmandoThe implementation of compact fiber-coupled light sources and devices represents a highly sought through technological goal, in wearable technologies, point-of-care units, telecommunication, and even quantum technology. In particular, a strong reduction of the overall device footprint, still ensuring a compact electrical contacting, would play an important role for electrically driven and electrically controlled devices. Here we show the integration of electrically pumped vertical-cavity surface-emitting lasers on multi-mode and single-mode fibers. The optimized integration technique is enabled by the advanced fiber-to-laser coupling design allowed by a detailed numerical investigation, as well as by an improved technological approach. While for the integration on multimode fibers, an important improvement over state-of-the-art is achieved, the integration on single-mode fiber is here demonstrated for the first time. All experimental results include reproducibility studies to show that the developed technique can be considered for larger scale implementations and are further supported by numerical investigation. This work marks an important step forward in the miniaturization of fiber-based optoelectronics devices which will be highly beneficial for various research and technology developments.