arXiv subjects

Carsten Ronning

Publications and source records attributed to Carsten Ronning.

At least 19 recordsLinked to original sources

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

Twist-angle Control of Nonlinear Interference in a ZnO Nanowire/Monolayer WSe$_2$ Hybrid Structure

Nanoscale devices that integrate materials of different dimensionalities (0D, 1D, and 2D) hold great potential for advanced applications in photonics and optoelectronics. A fundamental requirement for the development of such devices is the engineering and control of light-matter interactions beyond the simple enhancement or quenching of linear and nonlinear optical emission. In this study, we demonstrate control over nanoscale light-matter interactions by achieving twist-angle tunability of the nonlinear optical response in a hybrid system composed of a ZnO nanowire and a monolayer of WSe$_2$. By varying the relative orientation between the ZnO polar axis and the WSe$_2$ crystal axes, we realize both constructive and destructive interference in second-harmonic generation, as well as full material selectivity in second harmonic polarization-dependent measurements. These outcomes arise from the distinct dimensionalities and symmetries of the hybrid constituents, underscoring the generality of our approach. Thus, our work presents an advanced framework for the design and control of nonlinear light-matter interactions in nanoscale hybrid devices, thereby paving the way for their future use in photonic and optoelectronic technologies.

physics.optics↗

arXiv2026

Gallium phosphide on insulator for nanophotonics and quantum technologies

Gallium phosphide is a promising material platform for visible and near-infrared photonics and quantum technologies owing to its high refractive index, low optical absorption, and strong second-order nonlinearity. Here, we demonstrate the fabrication of GaP-on-insulator substrates by ion slicing. The splitting depth and exfoliation behavior of bulk GaP are tailored by controlling the He$^{+}$ ion implantation energy and fluence, enabling thin-film transfer onto amorphous substrates by anodic bonding and plasma-enhanced direct wafer bonding. Channeling Rutherford backscattering spectrometry and X-ray diffraction confirm that the transferred layers retain their single-crystalline structure, while implantation-induced disorder and optical absorption are substantially reduced by annealing at 500 {\deg}C and subsequent polishing. The annealed films exhibit linear optical properties approaching those of bulk GaP. In addition, a (110)-oriented GaP thin film shows the characteristic polarization dependence expected from the zinc-blende second-order nonlinear susceptibility tensor, demonstrating a near-pristine second-order nonlinear response. This flexible fabrication approach enables the integration of high-quality single-crystalline GaP with variable orientation for free-space and integrated nanophotonics as well as nonlinear and quantum optical devices.

physics.optics↗

arXiv2026

Frequency locking in lasing ZnO nanowire pairs

Frequency locking between coupled laser systems provides a powerful mechanism for stabilizing and controlling coherent emission, yet its implementation and applicability down to the nanoscale remains unknown and unexplored. Here, we demonstrate optical coupling and frequency locking in closely spaced ZnO nanowire lasers operating in the extreme near field (gap < 10 nm). We observe both full and partial frequency locking, manifested as the alignment of all or a subset of the lasing modes, by spatially controlling the optical excitation. We also observe single-mode lasing in a coupled nanowire pair where the multi-mode lasing of individual nanowires is suppressed. In contrast to previously reported coupled-cavity nanowire lasers, where spectral control arises from static filtering mechanisms such as the Vernier effect, our results indicate a dynamically established relationship between actively lasing nanowires. These findings establish frequency locking as a robust and tunable mechanism in nanowire lasers, opening new routes toward stabilized and controllable nanoscale light sources for integrated nanophotonic systems.

physics.optics↗

arXiv2026

Strong enhancement of Er3+ emission at room temperature in Si3N4 metasurfaces

We report a significant enhancement of room-temperature photoluminescence from trivalent erbium-doped (Er3+) silicon nitride (Si3N4) metasurfaces at the telecommunication wavelength prepared via ion implantation. The metasurfaces, consisting of periodic nanocylinder arrays, are designed to support Mie-type resonances that tailor the local density of optical states. By systematically optimizing the nanocylinder radii, we achieve a photoluminescence (PL) enhancement factor of ~18 at a radius of 390 nm after thermal annealing, which is in excellent agreement with our simulations. Time-resolved PL measurements reveal a nearly ten-fold reduction in luminescence lifetime, confirming that the enhancement is primarily driven by the Purcell effect. Furthermore, we demonstrate that the PL intensity is strongly dependent on the Er3+ ion implantation depth, with a four-fold increase in emission observed from 20 nm to 80 nm ion range. These results provide a robust pathway for integrating efficient, active light sources into CMOS-compatible photonic device.

physics.optics↗

arXiv2026

Enhancement of Circular Dichroism in Chiral Dielectric Metasurfaces by Ion Beam Irradiation

Resonant chiral dielectric metasurfaces can support circular dichroism exceeding that of natural materials, but their small dissipative losses simultaneously limit the maximization of circular dichroism, which inherently relies on absorption. Importantly, while the condition for optimal circular dichroism in resonant structures can be rigorously formulated based on the concept of critical coupling, controlling the amount of absorption experimentally, and ideally tuning it to the optimal value post-fabrication, remains elusive. Here, we experimentally tailor the dissipative losses of chiral bilayer dielectric metasurfaces post-fabrication using energetic ion beam irradiation. Specifically, we study the transmission characteristics of C4-symmetric chiral metasurface consisting of silicon nanocuboid arrays embedded in silica glass using polarization-resolved spectroscopy. We enhance the circular dichroism from 0.70 in the pristine, unirradiated metasurface to 0.85 after irradiation. Our experimental results are complemented by numerical simulations allowing us to retrieve the refractive index changes induced by the ion beam irradiation in the constituent materials of the metasurface. Our work offers a new approach to globally maximize optical chirality in engineered nanostructures, paving the way towards chiral emission and advanced polarization control applications

physics.optics↗

arXiv2025

Far-field directionality control of coupled InP nanowire lasers

Nanowire (NW) lasers hold great promise as compact, coherent on-chip light sources that are crucial for next-generation optical communication and imaging technologies. However, controlling their emission directionality has been hindered by the complexities of lasing mode engineering and fabrication. Here, we demonstrate spatially-engineered far-field emission from vertically emitting InP NW lasers by establishing precise control over the optical coupling between site-selective NWs, without relying on post-epitaxy transfer and alignment processes. Leveraging this process capability, we design and grow NW pairs and triplets that lase in the TE01 waveguide mode. We then demonstrate the ability to modify their far-field emission profiles from the signature doughnut-like emission to a double-lobed emission profile by changing their optical coupling gap, evidenced by closely matching simulation and experimental profiles. Moreover, through numerical simulations, we show further enhancement in the far-field directionality by arranging the NW laser pairs in a periodic array, demonstrating the feasibility of a directional lasing metasurface. Our results provide a foundation for efficient integration of coherent light generation and beam steering in on-chip light sources.

physics.optics↗

arXiv2024

Data-driven Discovery for Robust Optimization of Semiconductor Nanowire Lasers

Active wavelength-scale optoelectronic components are widely used in photonic integrated circuitry, however coherent sources of light -- namely optical lasers -- remain the most challenging component to integrate. Semiconductor nanowire lasers represent a flexible class of light source where each nanowire is both gain material and cavity; however, strong coupling between these properties and the performance leads to inhomogeneity across the population. While this has been studied and optimized for individual material systems, no architecture-wide insight is available. Here, nine nanowire laser material systems are studied and compared using 55,516 nanowire lasers to provide statistically robust insight into performance. These results demonstrate that, while it may be important to optimise internal quantum efficiency for certain materials, cavity effects are always critical. Our study provides a roadmap to optimize the performance of nanowire lasers made from any material: this can be achieved by ensuring a narrow spread of lengths and end-facet reflectivities.

physics.optics↗

arXiv2024

Hyper-doping of Silicon for Plasmonics in the Telecommunication Range

We investigate hyper-doping, a promising approach to introduce a high concentration of impurities into silicon beyond its solid solubility limit, for its potential applications in near-infrared plasmonics. We systematically explore the incorporation of dopants into silicon using ion implantation and pulsed laser melting annealing processes. Reflectance spectra analysis shows an achievable plasma wavelength of around 1.5 $\mu$m for dopant concentrations exceeding 4 at.%. Complex refractive index data for the doped silicon samples are extracted, revealing their potential for near-infrared plasmonic applications. Moreover, we propose a fabrication process that allows for the creation of hyper-doped silicon nanoparticles without the need for additional masking steps. Our research paves the way for designing CMOS-compatible plasmonic nanostructures operating in the telecommunication wavelength range. The study's findings offer significant insights into the utilization of hyper-doped silicon for advanced photonic and optoelectronic applications.

physics.optics↗

arXiv2024

Optical characterization of size- and substrate-dependent performance of ultraviolet hybrid plasmonic nanowire lasers

Nanowire-based plasmonic lasers are now established as nano-sources of coherent radiation, appearing as suitable candidates for integration into next-generation nanophotonic circuitry. However, compared to their photonic counterparts, their relatively high losses and large lasing thresholds still pose a burdening constraint on their scalability. In this study, the lasing characteristics of ZnO nanowires on Ag and Al substrates, operating as optically-pumped short-wavelength plasmonic nanolasers, are systematically investigated in combination with the size-dependent performance of the hybrid cavity. A hybrid nanomanipulation-assisted single nanowire optical characterization combined with high-throughput PL spectroscopy enables the correlation of the lasing characteristics to the metal substrate and the nanowire diameter. The results evidence that the coupling between excitons and surface plasmons is closely tied to the relationship between substrate dispersive behavior and nanowire diameter. Such coupling dictates the degree to which the lasing character, be it more plasmonic- or photonic-like, can define the stimulated emission features and, as a result, the device performance.

physics.optics↗

arXiv2024

Observation of dielectrically confined excitons in ultrathin GaN nanowires up to room temperature

The realization of semiconductor structures with stable excitons at room temperature is crucial for the development of excitonics and polaritonics. Quantum confinement has commonly been employed for enhancing excitonic effects in semiconductor heterostructures. Dielectric confinement, which is potentially much stronger, has proven to be more difficult to achieve because of the rapid nonradiative surface/interface recombination in hybrid dielectric-semiconductor structures. Here, we demonstrate intense excitonic emission from bare GaN nanowires with diameters down to 6 nm. The large dielectric mismatch between the nanowires and vacuum greatly enhances the Coulomb interaction, with the thinnest nanowires showing the strongest dielectric confinement and the highest radiative efficiency at room temperature. In situ monitoring of the fabrication of these structures allows one to accurately control the degree of dielectric enhancement. These ultrathin nanowires may constitute the basis for the fabrication of advanced low-dimensional structures with an unprecedented degree of confinement.

cond-mat.mes-hall↗

arXiv2023

Ion irradiation-induced sinking of Ag nanocubes into substrates

Ion irradiation can cause burrowing of nanoparticles in substrates, strongly depending on the material properties and irradiation parameters. In this study, we demonstrate that the sinking process can be accomplished with ion irradiation of cube-shaped Ag nanoparticles on top of silicon; how ion channeling affects the sinking rate; and underline the importance of the amorphous state of the substrate upon ion irradiation. Based on our experimental findings, the sinking process is described as being driven by capillary forces enabled by ion-induced plastic flow of the substrate.

cond-mat.mtrl-sci↗

arXiv2022

Broadband Four-Wave Mixing Enhanced by Plasmonic Surface Lattice Resonance and Localized Surface Plasmon Resonance in an Azimuthally Chirped Grating

Plasmonic enhancement of nonlinear light-matter interaction can be achieved via dedicated optimization of resonant plasmonic modes that are spectrally matched to the different wavelengths involved in the particular nonlinear optical process. In this work, we investigate the generation and enhancement of broadband four-wave mixing (FWM) in a plasmonic azimuthally chirped grating (ACG). The azimuthally varying grating periodicity in an ACG offers a well-defined channel to mediate the near field and the far field over a broad range of wavelengths. However, the particular mechanism responsible for field enhancement in such a platform depends on the interplay between the effects manifested by both the groove geometry and the grating's periodicity. This work delineates the collective contribution of groove geometry-dependent localized surface plasmon resonance (LSPR) and periodicity-dependent plasmonic surface lattice resonance (PSLR) over a broad range of wavelengths to bring into effect the enhancement of broadband FWM in an ACG.

physics.optics↗

arXiv2022

Tailoring Nanowire Lasing Modes via Coupling to Metal Gratings

Tailoring the emission of plasmonic nanowire-based lasers represents one of the major challenges in the field of nanoplasmonics, given the envisaged integration of such devices into on-chip all-optical circuits. In this study, we proposed a mode selection scheme based on distributed feedback, achieved via the external coupling of single zinc oxide nanowires to an aluminum grating, which enabled a quasi-single mode lasing action. The nano-manipulation of a single nanowire allowed for a reliable comparison of the lasing emission characteristics in both planar (i.e. nanowire on the metallic substrate) and on-grating configurations. We found that, by varying the orientation of the nanowire on the grating, only when the nano-cavity was perpendicular to the ridge direction, an additional peak emerged in the emission spectrum on the low-energy side of the gain envelope. As a consequence of the fulfillment of the Bragg condition, such a peak was attributed to a hybrid mode dominating the mode competition. Simulation results showed that the hybrid mode could be efficiently waveguided along the nanowire cavity and supported by localized plasmon polaritons building up at the raised features ("fences") on top of the metal grating ridges. Moreover, the hybrid mode was found to experience an extra reflectance of nearly 50% across the grating periods, in addition to that provided by the nanowire end facets.

physics.optics↗

arXiv2022

Lasing modes in ZnO nanowires coupled to planar metals

Semiconductor nanowire lasers can be subject to modifications of their lasing threshold resulting from a variation of their environment. A promising choice is to use metallic substrates to gain access to low-volume Surface-Plasmon-Polariton (SPP) modes. We introduce a simple, yet quantitatively precise model that can serve to describe mode competition in nanowire lasers on metallic substrates. We show that an aluminum substrate can decrease the lasing threshold for ZnO nanowire lasers while for a silver substrate, the threshold increases compared with a dielectric substrate. Generalizing from these findings, we make predictions describing the interaction between planar metals and semiconductor nanowires, which allow to guide future improvements of highly-integrated laser sources.

physics.optics↗

arXiv2022

Heavily doped zinc oxide with plasma frequencies in the telecommunication wavelength range

We demonstrate heavy and hyper doping of ZnO by a combination of gallium (Ga) ion implantation using a focused ion beam (FIB) system and post-implantation laser annealing. Ion implantation allows for the incorporation of impurities with nearly arbitrary concentrations, and the laser-annealing process enables dopant activation close to or beyond the solid-solubility limit of Ga in ZnO. We achieved heavily doped ZnO:Ga with free-carrier concentrations of ~10^21 cm^(-3), resulting in a plasma wavelength of 1.02 um, which is substantially shorter than the telecommunication wavelength of 1.55 um. Thus, our approach enables the control of the plasma frequency of ZnO from the far infrared down to 1.02 um, providing a promising plasmonic material for applications in this regime.

physics.app-ph↗

arXiv2022

Nonlinear optical signal generation mediated by a plasmonic azimuthally chirped grating

The deployment of plasmonic nanostructures to enhance nonlinear signal generation requires effective far-to-near field coupling and phase matching for frequency conversion. While the latter can be easily achieved at plasmonic hotspots, the former is an antenna problem that requires dedicated structural design and optimization. Plasmonic gratings are a simple but effective platform for nonlinear signal generation since they provide a well-defined momentum for photon-plasmon coupling and local hotspots for frequency conversion. In this work, a plasmonic azimuthally chirped grating (ACG), which provides spatially resolved broadband momentum for photon-plasmon coupling, was exploited to investigate the plasmonic enhancement effect in two nonlinear optical processes, namely two-photon photoluminescence (TPPL) and second-harmonic generation (SHG). The spatial distributions of the nonlinear signals were determined experimentally by hyperspectral mapping with ultrashort pulsed excitation. The experimental spatial distributions of nonlinear signals agree very well with the analytical prediction based solely on photon-plasmon coupling with the momentum of the ACG, revealing the antenna function of the grating in plasmonic nonlinear signal generation. This work highlights the importance of the antenna effect of the gratings for nonlinear signal generation and provides insight into the enhancement mechanism of plasmonic gratings in addition to local hotspot engineering.

physics.optics↗

arXiv2022

Tuning nanowire lasers via hybridization with two-dimensional materials

Mixed dimensional hybrid structures have recently gained increasing attention as promising building blocks for novel electronic and optoelectronic devices. In this context, hybridization of semiconductor nanowires with two-dimensional materials could offer new ways to control and modulate lasing at the nanoscale. In this work, we deterministically fabricate hybrid mixed-dimensional heterostructures composed of ZnO nanowires and MoS2 monolayers with micrometer control over their relative position. First, we show that our deterministic fabrication method does not degrade the optical properties of the ZnO nanowires. Second, we demonstrate that the lasing wavelength of ZnO nanowires can be tuned by several nanometers by hybridization with CVD-grown MoS2 monolayers. We assign this spectral shift of the lasing modes to an efficient carrier transfer at the heterointerface and the subsequent increase of the optical band gap in ZnO (Moss-Burstein effect).

physics.optics↗