arXiv subjects

Jorik van de Groep

Publications and source records attributed to Jorik van de Groep.

14 recordsLinked to original sources

arXiv2026

All-Optical Control over Nonlocality for Ultrafast Image Processing with an Excitonic Metasurface

Image processing lies at the foundation of many modern technologies, such as augmented reality and autonomous driving, yet conventional digital approaches remain energy-intensive and limited in speed. Nonlocal metasurfaces - 2D structures engineered at the nanoscale to support delocalized, dispersion engineered resonances - provide a fast, energy-efficient and ultrathin platform to perform image processing directly on the light path. Introducing tunability in this platform is an outstanding challenge, and would enable dynamic real-time control over the implemented processing operation, facilitating flexible integration into adaptive and multifunctional photonic architectures. Here, we demonstrate optically tunable edge detection at ultrafast speeds by integrating a dielectric nonlocal metasurface with multilayer WS2, whose strong exciton-driven optical response enables dynamic control of the metasurface nonlocality at sub-ps speeds. Using resonant optical pumping of the A-exciton in WS2, the metasurface transfer function is rapidly switched from edge detection to bright-field imaging by tuning its spatial nonlocality. Operating in the visible spectral range at a wavelength around 700 nm, the device shows ultrafast switching times and reaches an amplitude modulation depth of 11.5 dB for normal incident light. This approach provides a reconfigurable, ultrathin, all-optical platform for adaptive optical computing systems and highlights the potential of the highly nonlinear properties of 2D materials for active metasurfaces at ultrafast speeds.

physics.optics↗

arXiv2026

Ultrafast tuning of the focusing efficiency of a nonlinear atomically thin lens

Control over light focusing is paramount for optical and imaging systems. However, its implementation in active and integrated nanophotonic devices is hindered by the bulky and static nature of standard lenses. Here, we show that Fresnel Zone Plate Lenses (FZPL) based on a monolayer Transitional Metal Dichalcogenide are a viable solution to the challenges of miniaturization, integration, and active control of the focusing efficiency, featuring both ultrafast and large modulation depth. Using a monolayer $WSe_2$ FZPL, we demonstrate all-optical ultrafast ($\sim$ ps) modulation of the focusing efficiency close to $\sim$30\%, that we achieve by exploiting the nonlinear exciton-resonant enhancement and modulation of second harmonic generation.

physics.optics↗

arXiv2026

Hybrid-2D Excitonic Metasurfaces for Complex Amplitude Modulation

Dynamic control of visible light is crucial for technologies such as holographic displays and adaptive optics. Passive metasurfaces can shape wavefronts at the subwavelength scale and active metasurfaces promise to extend this functionality into the temporal domain. However, existing metasurfaces for dynamic phase manipulation typically cannot deliver phase modulation across a broad range without causing variations in the scattering amplitude. Here, we use an inverse-design pipeline to numerically demonstrate a hybrid-2D excitonic metasurface platform offering independent amplitude and phase control in the visible regime. Harnessing the gate-tunable excitonic response of monolayer WS2 retrieved from experiments, we design a pi-phase modulator with a uniform amplitude profile. Adding a second tunable monolayer, we achieve independent control of the amplitude and phase over the full 0-2pi phase range, which we leverage for a reconfigurable beam-steering metadevice. Our results demonstrate how hybrid-2D excitonic metasurfaces enable electrically tunable wavefront shaping in the visible regime.

physics.optics↗

arXiv2026

Large-Area Deterministic Stamping of 2D Materials on Arbitrarily Patterned Surfaces

2D materials and their monolayers have attracted widespread interest by virtue of their unique electronic and optical properties. In addition to their remarkable physical characteristics, their atomically thin nature enables their integration in ultra-compact photonic and electronic devices, with potential for dynamic tunability via strain, charge carrier modulation or heterostructure engineering. While early research relied on micrometer-scale mechanically exfoliated flakes, recent advances, particularly gold-assisted exfoliation of transition metal dichalcogenides (TMDCs), have enabled the preparation of high-quality, large-area monolayers, opening new opportunities for scalable device integration. For the field of nanophotonics in particular, the ability to transfer large-area 2D materials onto both flat and patterned substrates is essential for the development of functional devices. However, existing transfer techniques are often limited in scalability, and compatibility with structured surfaces. Here, we present a versatile and reliable transfer method of large-area monolayers and hBN/monolayer heterostructures onto both flat and nanostructured substrates. Our approach, based on the physical properties of low-density polyethylene, preserves the intrinsic optical quality of the materials and is compatible with a variety of device architectures. We demonstrate its applicability by fabricating devices that modulate the photoluminescence of TMDC monolayers through the manipulation of the photonic environment, strain or electrical gating. We further demonstrate the fabrication of van der Waals heterostructures using the same method. By enabling clean transfer of a wide range of monolayers and heterostructures, this technique offers a practical pathway for the development of next-generation optoelectronic platforms with improved functionality, scalability, and tunability.

cond-mat.mes-hall↗

arXiv2026

Finite-Size Effects in Nonlocal Metasurfaces

Metasurfaces leveraging nonlocal resonances enable narrowband spectral control and strong near-fields, with applications spanning augmented reality, biosensing, and nonlinear optics. However, the large spa- tial extent of these modes also poses new challenges: finite-size effects often deteriorate the performance of practical, footprint-limited devices. Here, we develop a spatiotemporal coupled-mode theory model that intuitively and quantitatively captures how finite size affects the scattering response of nonlocal metasurfaces. This reveals that, when the modal propagation length becomes constrained by the phys- ical interaction length, the scattered field shows strong interference fringes and linewidth broadening. We derive an expression for the quality factor that incorporates an additional edge-loss channel, demon- strating that the stored energy and effective lifetime scale exponentially with the interaction length. We validate these predictions experimentally using position- and momentum-resolved spectroscopy on a 30-micron-wide metasurface. Overall, this work formalizes the impact of finite size on the scattering re- sponse of nonlocal photonic systems, and provides handles on how to minimize the impact of finite-size effects in metasurface design.

physics.optics↗

arXiv2025

Temperature-dependent excitonic light manipulation with atomically-thin optical elements

Monolayer 2D semiconductors, such as WS2, exhibit uniquely strong light-matter interactions due to exciton resonances that enable atomically-thin optical elements. Similar to geometry-dependent plasmon and Mie resonances, these intrinsic material resonances offer coherent and tunable light scattering. Thus far, the impact of the excitons temporal dynamics on the performance of such excitonic metasurfaces remains unexplored. Here, we show how the excitonic decay rates dictate the focusing efficiency of an atomically-thin lens carved directly out of exfoliated monolayer WS2. By isolating the coherent exciton radiation from the incoherent background in the focus of the lens, we obtain a direct measure of the role of exciton radiation in wavefront shaping. Furthermore, we investigate the influence of exciton-phonon scattering by characterizing the focusing efficiency as a function of temperature, demonstrating an increased optical efficiency at cryogenic temperatures. Our results provide valuable insights in the role of excitonic light scattering in 2D nanophotonic devices.

physics.optics↗

arXiv2025

Photonics in Flatland: Challenges and Opportunities for Nanophotonics with 2D Semiconductors

Two-dimensional (2D) semiconductors are emerging as a versatile platform for nanophotonics, offering unprecedented tunability in optical properties through exciton resonance engineering, van der Waals heterostructuring, and external field control. These materials enable active optical modulation, single-photon emission, quantum photonics, and valleytronic functionalities, paving the way for next-generation optoelectronic and quantum photonic devices. However, key challenges remain in achieving large-area integration, maintaining excitonic coherence, and optimizing amplitude-phase modulation for efficient light manipulation. Advances in fabrication, strain engineering, and computational modelling will be crucial to overcoming these limitations. This perspective highlights recent progress in 2D semiconductor-based nanophotonics, emphasizing opportunities for scalable integration into photonics.

physics.optics↗

arXiv2025

Roadmap for Photonics with 2D Materials

Triggered by the development of exfoliation and the identification of a wide range of extraordinary physical properties in self-standing films consisting of one or few atomic layers, two-dimensional (2D) materials such as graphene, transition metal dichalcogenides (TMDs), and other van der Waals (vdW) crystals currently constitute a wide research field protruding in multiple directions in combination with layer stacking and twisting, nanofabrication, surface-science methods, and integration into nanostructured environments. Photonics encompasses a multidisciplinary collection of those directions, where 2D materials contribute with polaritons of unique characteristics such as strong spatial confinement, large optical-field enhancement, long lifetimes, high sensitivity to external stimuli (e.g., electric and magnetic fields, heating, and strain), a broad spectral range from the far infrared to the ultraviolet, and hybridization with spin and momentum textures of electronic band structures. The explosion of photonics with 2D materials as a vibrant research area is producing breakthroughs, including the discovery and design of new materials and metasurfaces with unprecedented properties as well as applications in integrated photonics, light emission, optical sensing, and exciting prospects for applications in quantum information, and nanoscale thermal transport. This Roadmap summarizes the state of the art in the field, identifies challenges and opportunities, and discusses future goals and how to meet them through a wide collection of topical sections prepared by leading practitioners.

cond-mat.mtrl-sci↗

arXiv2025

Electrically tunable strong coupling in a hybrid-2D excitonic metasurface for optical modulation

Atomically thin semiconductors exhibit tunable exciton resonances that can be harnessed for dynamic manipulation of visible light in ultra-compact metadevices. However, the rapid nonradiative decay and dephasing of excitons at room temperature limits current active excitonic metasurfaces to few-percent efficiencies. Here, we leverage the combined merits of pristine 2D heterostructures and non-local dielectric metasurfaces to enhance the excitonic light-matter interaction, achieving strong and electrically tunable exciton-photon coupling at ambient conditions in a hybrid-2D excitonic metasurface. Using this, we realize a free-space optical modulator and experimentally demonstrate 9.9 dB of reflectance modulation. The electro-optic response, characterized by a continuous transition from strong to weak coupling, is mediated by gating-induced variations in the free carrier concentration altering the excitons nonradiative decay rate. These results highlight how hybrid-2D excitonic metasurfaces offer novel opportunities to realize nanophotonic devices for active wavefront manipulation and optical communication.

physics.optics↗

arXiv2025

Mechano-optical metasurfaces

Tunable metasurfaces enable active and on-demand control over optical wavefronts through reconfigurable scattering of resonant nanostructures. Here, we present novel insights inspired by mechanical metamaterials to achieve giant tunability in mechano-optical metasurfaces where the mechanical metamaterial and optical metasurfaces are integrated in a single nanopatterned material. In a first design, judiciously engineered cuts in a flexible substrate enable large, strain-induced extension of the inter-particle spacing, tuning a high quality-factor resonance in a silicon nanoparticle array across a very broad spectral range. In a second design, we eliminate the substrate and demonstrate a nanopatterned silicon membrane that simultaneously functions as a mechanical metamaterial and an optical metasurface with large tunability. Our results highlight a promising route toward active metasurfaces, with potential applications in tunable filters, reconfigurable lenses, and dynamic wavefront shaping.

physics.optics↗

arXiv2022

Impact of substrates and quantum effects on exciton line shapes of 2D semiconductors at room temperature

Exciton resonances in monolayer transition-metal dichalcogenides (TMDs) provide exceptionally strong light-matter interaction at room temperature. Their spectral line shape is critical in the design of a myriad of optoelectronic devices, ranging from solar cells to quantum information processing. However, disorder resulting from static inhomogeneities and dynamical fluctuations can significantly impact the line shape. Many recent works experimentally evaluate the optical properties of TMD monolayers placed on a substrate and the line shape is typically linked directly to the material's quality. Here, we highlight that the interference of the substrate and TMD reflections can strongly influence the line shape. We further show how basic, room-temperature reflection measurement allow investigation of the quantum mechanical exciton dynamics by systematically controlling the substrate reflection with index-matching oils. By removing the substrate contribution with a properly chosen oil, we can extract the excitonic decay rates including the quantum mechanical dephasing rate. The results provide valuable guidance for the engineering of exciton line shapes in layered nanophotonic systems.

cond-mat.mes-hall↗

arXiv2022

Tutorial: Exciton resonances for atomically-thin optics

Metasurfaces enable flat optical elements by leveraging optical resonances in metallic or dielectric nanoparticles to obtain accurate control over the amplitude and phase of the scattered light. While highly efficient, these resonances are static and difficult to tune actively. Exciton resonances in atomically thin 2D semiconductors provide a novel and uniquely strong resonant light-matter interaction, which presents a new opportunity for optical metasurfaces. Their resonant properties are intrinsic to the band structure of the material and do not rely on nanoscale patterns and are highly tunable using external stimuli. In this tutorial, we present the role that excitons resonances can play for atomically-thin optics. We describe the essentials of metasurface physics, provide a background on exciton physics, as well as a comprehensive overview of excitonic materials. Excitons demonstrate to provide new degrees of freedom and enhanced light-matter interactions in hybrid metasurfaces through coupling with metallic and dielectric metasurfaces. Using the high sensitivity of excitons to the medium's electron density, the first demonstrations of electrically-tunable nanophotonic devices and atomically-thin optical elements are also discussed. The future of excitons in metasurfaces looks promising, while the main challenge lies in large-area growth and precise integration of high-quality materials.

physics.optics↗

arXiv2021

Nonlocal metasurfaces for spectrally decoupled wavefront manipulation and eye tracking

Metasurface-based optical elements typically manipulate light waves by imparting space-variant changes in the amplitude and phase with a dense array of scattering nanostructures. The highly-localized and low optical-quality-factor (Q) modes of nanostructures are beneficial for wavefront-shaping as they afford quasi-local control over the electromagnetic fields. However, many emerging imaging, sensing, communication, display, and non-linear optics applications instead require flat, high-Q optical elements that provide notable energy storage and a much higher degree of spectral control over the wavefront. Here, we demonstrate high-Q, nonlocal metasurfaces with atomically-thin metasurface elements that offer notably enhanced light-matter interaction and fully-decoupled optical functions at different wavelengths. We illustrate a possible use of such a flat optic in eye tracking for eye-wear. Here, a metasurface patterned on a regular pair of eye-glasses provides an unperturbed view of the world across the visible spectrum and redirects near-infrared light to a camera to allow imaging of the eye.

physics.optics↗

arXiv2013

Transparent conducting silver nanowire networks

We present a transparent conducting electrode composed of a periodic two-dimensional network of silver nanowires. Networks of Ag nanowires are made with wire diameters of 45-110 nm and pitch of 500, 700 and 1000 nm. Anomalous optical transmission is observed, with an averaged transmission up to 91% for the best transmitting network and sheet resistances as low as 6.5 Ω/sq for the best conducting network. Our most dilute networks show lower sheet resistance and higher optical transmittance than an 80 nm thick layer of ITO sputtered on glass. By comparing measurements and simulations we identify four distinct physical phenomena that govern the transmission of light through the networks: all related to the excitation of localized surface plasmons and surface plasmon polaritons on the wires. The insights given in this paper provide the key guidelines for designing high-transmittance and low-resistance nanowire electrodes for optoelectronic devices, including thin-film solar cells. For these latter, we discuss the general design principles to use the nanowire electrodes also as a light trapping scheme.

physics.optics↗