Staff directory Klaas-Jan Tielrooij

Klaas-Jan Tielrooij

Junior Group Leader
RYC 2017
Ultrafast Dynamics in Nanoscale Systems



  • Grating-Graphene Metamaterial as a Platform for Terahertz Nonlinear Photonics

    Deinert J.-C., Alcaraz Iranzo D., Pérez R., Jia X., Hafez H.A., Ilyakov I., Awari N., Chen M., Bawatna M., Ponomaryov A.N., Germanskiy S., Bonn M., Koppens F.H.L., Turchinovich D., Gensch M., Kovalev S., Tielrooij K.-J. ACS Nano; 15 (1): 1145 - 1154. 2021. 10.1021/acsnano.0c08106. IF: 14.588

    Nonlinear optics is an increasingly important field for scientific and technological applications, owing to its relevance and potential for optical and optoelectronic technologies. Currently, there is an active search for suitable nonlinear material systems with efficient conversion and a small material footprint. Ideally, the material system should allow for chip integration and room-temperature operation. Two-dimensional materials are highly interesting in this regard. Particularly promising is graphene, which has demonstrated an exceptionally large nonlinearity in the terahertz regime. Yet, the light-matter interaction length in two-dimensional materials is inherently minimal, thus limiting the overall nonlinear optical conversion efficiency. Here, we overcome this challenge using a metamaterial platform that combines graphene with a photonic grating structure providing field enhancement. We measure terahertz third-harmonic generation in this metamaterial and obtain an effective third-order nonlinear susceptibility with a magnitude as large as 3 × 10-8 m2/V2, or 21 esu, for a fundamental frequency of 0.7 THz. This nonlinearity is 50 times larger than what we obtain for graphene without grating. Such an enhancement corresponds to a third-harmonic signal with an intensity that is 3 orders of magnitude larger due to the grating. Moreover, we demonstrate a field conversion efficiency for the third harmonic of up to ∼1% using a moderate field strength of ∼30 kV/cm. Finally, we show that harmonics beyond the third are enhanced even more strongly, allowing us to observe signatures of up to the ninth harmonic. Grating-graphene metamaterials thus constitute an outstanding platform for commercially viable, CMOS-compatible, room-temperature, chip-integrated, THz nonlinear conversion applications. © 2021 American Chemical Society. All rights reserved.

  • Long-lived charge separation following pump-wavelength–dependent ultrafast charge transfer in graphene/WS2 heterostructures

    Fu S., du Fossé I., Jia X., Xu J., Yu X., Zhang H., Zheng W., Krasel S., Chen Z., Wang Z.M., Tielrooij K.-J., Bonn M., Houtepen A.J., Wang H.I. Science Advances; 7 (9, eabd9061) 2021. 10.1126/sciadv.abd9061. IF: 13.117

    Van der Waals heterostructures consisting of graphene and transition metal dichalcogenides have shown great promise for optoelectronic applications. However, an in-depth understanding of the critical processes for device operation, namely, interfacial charge transfer (CT) and recombination, has so far remained elusive. Here, we investigate these processes in graphene-WS2 heterostructures by complementarily probing the ultrafast terahertz photoconductivity in graphene and the transient absorption dynamics in WS2 following photoexcitation. We observe that separated charges in the heterostructure following CT live extremely long: beyond 1 ns, in contrast to ~1 ps charge separation reported in previous studies. This leads to efficient photogating of graphene. Furthermore, for the CT process across graphene-WS2 interfaces, we find that it occurs via photo-thermionic emission for sub-A-exciton excitations and direct hole transfer from WS2 to the valence band of graphene for above-A-exciton excitations. These findings provide insights to further optimize the performance of optoelectronic devices, in particular photodetection. Copyright © 2021 The Authors, some rights reserved;


  • Fast electrical modulation of strong near-field interactions between erbium emitters and graphene

    Cano D., Ferrier A., Soundarapandian K., Reserbat-Plantey A., Scarafagio M., Tallaire A., Seyeux A., Marcus P., Riedmatten H., Goldner P., Koppens F.H.L., Tielrooij K.-J. Nature Communications; 11 (1, 4094) 2020. 10.1038/s41467-020-17899-7. IF: 12.121

    Combining the quantum optical properties of single-photon emitters with the strong near-field interactions available in nanophotonic and plasmonic systems is a powerful way of creating quantum manipulation and metrological functionalities. The ability to actively and dynamically modulate emitter-environment interactions is of particular interest in this regard. While thermal, mechanical and optical modulation have been demonstrated, electrical modulation has remained an outstanding challenge. Here we realize fast, all-electrical modulation of the near-field interactions between a nanolayer of erbium emitters and graphene, by in-situ tuning the Fermi energy of graphene. We demonstrate strong interactions with a >1000-fold increased decay rate for ~25% of the emitters, and electrically modulate these interactions with frequencies up to 300 kHz – orders of magnitude faster than the emitter’s radiative decay (~100 Hz). This constitutes an enabling platform for integrated quantum technologies, opening routes to quantum entanglement generation by collective plasmon emission or photon emission with controlled waveform. © 2020, The Author(s).

  • Plasmonic antenna coupling to hyperbolic phonon-polaritons for sensitive and fast mid-infrared photodetection with graphene

    Castilla S., Vangelidis I., Pusapati V.-V., Goldstein J., Autore M., Slipchenko T., Rajendran K., Kim S., Watanabe K., Taniguchi T., Martín-Moreno L., Englund D., Tielrooij K.-J., Hillenbrand R., Lidorikis E., Koppens F.H.L. Nature Communications; 11 (1, 4872) 2020. 10.1038/s41467-020-18544-z. IF: 12.121

    Integrating and manipulating the nano-optoelectronic properties of Van der Waals heterostructures can enable unprecedented platforms for photodetection and sensing. The main challenge of infrared photodetectors is to funnel the light into a small nanoscale active area and efficiently convert it into an electrical signal. Here, we overcome all of those challenges in one device, by efficient coupling of a plasmonic antenna to hyperbolic phonon-polaritons in hexagonal-BN to highly concentrate mid-infrared light into a graphene pn-junction. We balance the interplay of the absorption, electrical and thermal conductivity of graphene via the device geometry. This approach yields remarkable device performance featuring room temperature high sensitivity (NEP of 82 pW/Hz) and fast rise time of 17 nanoseconds (setup-limited), among others, hence achieving a combination currently not present in the state-of-the-art graphene and commercial mid-infrared detectors. We also develop a multiphysics model that shows very good quantitative agreement with our experimental results and reveals the different contributions to our photoresponse, thus paving the way for further improvement of these types of photodetectors even beyond mid-infrared range. © 2020, The Author(s).

  • Terahertz Nonlinear Optics of Graphene: From Saturable Absorption to High-Harmonics Generation

    Hafez H.A., Kovalev S., Tielrooij K.-J., Bonn M., Gensch M., Turchinovich D. Advanced Optical Materials; 8 (3, 1900771) 2020. 10.1002/adom.201900771. IF: 8.286

    Graphene has long been predicted to show exceptional nonlinear optical properties, especially in the technologically important terahertz (THz) frequency range. Recent experiments have shown that this atomically thin material indeed exhibits possibly the largest nonlinear coefficients of any material known to date, paving the way for practical graphene-based applications in ultrafast (opto-)electronics operating at THz rates. Here the advances in the booming field of nonlinear THz optics of graphene are reported, and the state-of-the-art understanding of the nature of the nonlinear interaction of graphene with the THz fields based on the thermodynamic model of electron transport in graphene is described. A comparison between different mechanisms of nonlinear interaction of graphene with light fields in THz, infrared, and visible frequency ranges is also provided. Finally, the perspectives for the expected technological applications of graphene based on its extraordinary THz nonlinear properties are summarized. This report covers the evolution of the field of THz nonlinear optics of graphene from the very pioneering to the state-of-the-art works. It also serves as a concise overview of the current understanding of THz nonlinear optics of graphene and as a compact reference for researchers entering the field, as well as for the technology developers. © 2019 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim


  • Control of Terahertz Nonlinearity in Graphene by Gating

    Hafez H.A., Tielrooij K.-J., Bonn M., Turchinovich D. International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz; 2019-September (8874288) 2019. 10.1109/IRMMW-THz.2019.8874288.

    We study the dependence of the terahertz (THz) nonlinearity of graphene and its temporal dynamics on the free carrier concentration by THz-pump/THz-probe spectroscopy of a gated graphene at room temperature. The strong THz nonlinearity is attributed to electron heating by the driving THz field and shows a drastic dependence on the background electron concentration, demonstrating a wide-range tunability of the THz nonlinearity of graphene. © 2019 IEEE.

  • Fast and Sensitive Terahertz Detection Using an Antenna-Integrated Graphene pn Junction

    Castilla S., Terrés B., Autore M., Viti L., Li J., Nikitin A.Y., Vangelidis I., Watanabe K., Taniguchi T., Lidorikis E., Vitiello M.S., Hillenbrand R., Tielrooij K.-J., Koppens F.H.L. Nano Letters; 19 (5): 2765 - 2773. 2019. 10.1021/acs.nanolett.8b04171. IF: 12.279

    Although the detection of light at terahertz (THz) frequencies is important for a large range of applications, current detectors typically have several disadvantages in terms of sensitivity, speed, operating temperature, and spectral range. Here, we use graphene as a photoactive material to overcome all of these limitations in one device. We introduce a novel detector for terahertz radiation that exploits the photothermoelectric (PTE) effect, based on a design that employs a dual-gated, dipolar antenna with a gap of ?100 nm. This narrow-gap antenna simultaneously creates a pn junction in a graphene channel located above the antenna and strongly concentrates the incoming radiation at this pn junction, where the photoresponse is created. We demonstrate that this novel detector has an excellent sensitivity, with a noise-equivalent power of 80 pW/Hz at room temperature, a response time below 30 ns (setup-limited), a high dynamic range (linear power dependence over more than 3 orders of magnitude) and broadband operation (measured range 1.8-4.2 THz, antenna-limited), which fulfills a combination that is currently missing in the state-of-the-art detectors. Importantly, on the basis of the agreement we obtained between experiment, analytical model, and numerical simulations, we have reached a solid understanding of how the PTE effect gives rise to a THz-induced photoresponse, which is very valuable for further detector optimization. © 2019 American Chemical Society.

  • Ionic permeability and interfacial doping of graphene on SiO2 measured with Terahertz photoconductivity measurements

    Jia X., Tielrooij K.-J., Bonn M., Wang H.I. International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz; 2019-September (8874148) 2019. 10.1109/IRMMW-THz.2019.8874148.

    Graphene has been widely used in various electrochemical applications owing to its outstanding electrical and chemical properties. The presence of electrolyte at the graphene surfaces affects graphene's electronic properties, especially its electrical conductivity. The precise mechanism underlying the graphene-electrolyte interaction has remained elusive, despite the importance of graphene for electrochemical applications. Here, we employ optical-pump THz-probe spectroscopy as a contact-free and all-optical means to investigate the impact of cations on graphene conductivity in the electrolyte. We reveal ionic permeability though graphene, resulting in an interfacial doping effect in SiO2-supported graphene. © 2019 IEEE.

  • Kinetic Ionic Permeation and Interfacial Doping of Supported Graphene

    Jia X., Hu M., Soundarapandian K., Yu X., Liu Z., Chen Z., Narita A., Müllen K., Koppens F.H.L., Jiang J., Tielrooij K.-J., Bonn M., Wang H.I. Nano Letters; 19 (12): 9029 - 9036. 2019. 10.1021/acs.nanolett.9b04053. IF: 12.279

    Due to its outstanding electrical properties and chemical stability, graphene finds widespread use in various electrochemical applications. Although the presence of electrolytes strongly affects its electrical conductivity, the underlying mechanism has remained elusive. Here, we employ terahertz spectroscopy as a contact-free means to investigate the impact of ubiquitous cations (Li+, Na+, K+, and Ca2+) in aqueous solution on the electronic properties of SiO2-supported graphene. We find that, without applying any external potential, cations can shift the Fermi energy of initially hole-doped graphene by ∼200 meV up to the Dirac point, thus counteracting the initial substrate-induced hole doping. Remarkably, the cation concentration and cation hydration complex size determine the kinetics and magnitude of this shift in the Fermi level. Combined with theoretical calculations, we show that the ion-induced Fermi level shift of graphene involves cationic permeation through graphene. The interfacial cations located between graphene and SiO2 electrostatically counteract the substrate-induced hole doping effect in graphene. These insights are crucial for graphene device processing and further developing graphene as an ion-sensing material. © 2019 American Chemical Society.

  • Surface-Specific Spectroscopy of Water at a Potentiostatically Controlled Supported Graphene Monolayer

    Dreier L.B., Liu Z., Narita A., Van Zadel M.-J., Müllen K., Tielrooij K.-J., Backus E.H.G., Bonn M. Journal of Physical Chemistry C; 123 (39): 24031 - 24038. 2019. 10.1021/acs.jpcc.9b05844. IF: 4.309

    Knowledge of the structure of interfacial water molecules at electrified solid materials is the first step toward a better understanding of important processes at such surfaces, in, e.g., electrochemistry, atmospheric chemistry, and membrane biophysics. As graphene is an interesting material with multiple potential applications such as in transistors or sensors, we specifically investigate the graphene-water interface. We use sum-frequency generation spectroscopy to investigate the pH- and potential-dependence of the interfacial water structure in contact with a chemical vapor deposited (CVD) grown graphene surface. Our results show that the SFG signal from the interfacial water molecules at the graphene layer is dominated by the underlying substrate and that there are water molecules between the graphene and the (hydrophilic) supporting substrate. © 2019 American Chemical Society.

  • Ultrathin Eu- and Er-Doped Y2O3 Films with Optimized Optical Properties for Quantum Technologies

    Scarafagio M., Tallaire A., Tielrooij K.-J., Cano D., Grishin A., Chavanne M.-H., Koppens F.H.L., Ringuedé A., Cassir M., Serrano D., Goldner P., Ferrier A. Journal of Physical Chemistry C; 123 (21): 13354 - 13364. 2019. 10.1021/acs.jpcc.9b02597. IF: 4.309

    Atomic layer deposited (ALD) Y2O3 thin films have been thoroughly investigated for optical or electronic applications. The coherent spectroscopy of lanthanide ions doped into this material has also recently attracted increasing interest in the field of quantum technologies for which they are considered promising candidates in quantum memories or as spin-photon interfaces. However, these most demanding applications require a deep control over the local positioning of the ions and their close environment in the crystalline matrix. This study focuses on the structural as well as optical properties of Eu3+ and Er3+ dopants in Y2O3 using photoluminescence (PL), luminescence decay times, and inhomogeneous line width (Γinh) measurements within this particular context. While as-grown ALD films do not provide an ideal host for the emitters, we demonstrate that by optimizing the deposition conditions and using appropriate annealing post treatments narrow inhomogeneous lines can be obtained for the 7F0↔5D0 transition of Eu3+ even for nanoscale films. Furthermore, about 1.5 ms lifetime has been measured for the infrared telecom transition of Er in ultrathin films (<10 nm), which is an order of magnitude higher than in nanoparticles of the same size. These results validate optimized rare-earth-doped ALD Y2O3 films as a suitable platform for photonics applications where few-nanometer-thick films with well-localized emitters are mandatory. This approach provides the first building blocks toward the development of more complex devices for quantum sensing or hybrid structures coupled with other systems such as two-dimensional materials. © 2019 American Chemical Society.