arXiv subjects

Connor Heimig

Publications and source records attributed to Connor Heimig.

9 recordsLinked to original sources

arXiv2026

Plasmonic Fourier Surfaces Revisited: Relating Bandgaps with Bound States in the Continuum

Periodically corrugated metal interfaces supporting surface plasmon polaritons (SPPs) belong to the earliest nanoplasmonic platforms. Even simplest reliefs described by a few harmonics - plasmonic Fourier surfaces - display markedly different far-field signatures depending on the corrugation depth and symmetry: shallow reliefs exhibit a plasmonic bandgap (PBG) between two hybridized SPP standing waves, while deeper reliefs support asymmetry-induced single sharp resonances, termed over the last decade as quasi-bound states in the continuum (qBICs). Although these spectral features have long been observed experimentally and treated empirically, the underlying eigenmode evolution connecting the shallow and deep corrugation regimes has remained largely unexplored. Here we revisit this long-standing problem by analyzing it in terms of modern eigenstate formalism. Starting from the Rayleigh hypothesis, we develop a concise first-principle analytical description that explicitly captures how one eigenmode transforms from a dark bound state into an observable qBIC, while the other turns from bright into an overcoupled, unobservable state - thus unifying the SPP manifestations featuring PBG and qBIC within the same eigenmode framework. Finally, we demonstrate the practical relevance of the theory by showing how precise eigenstate engineering can enhance the SPP refractive index sensitivity.

physics.optics↗

arXiv2026

Orbital Angular Momentum Locking via Bound States in the Continuum

Optical vortices are electromagnetic fields twisting around a phase singularity, resulting in quantized orbital angular momentum (OAM). When such vortices are formed by evanescent hybrid light-matter quasiparticles known as polaritons, they are referred to as polaritonic vortices (PVs). The nanometer-scale topologically robust features of such PVs promise to enable applications for lasing and thermal emission at deeply subwavelength scales. However, many conventional techniques are prone to producing multimode PVs due to poor mode selectivity, resulting in OAM mixing that degrades vortex purity and limits their performance for high-fidelity optical information encoding and multi-dimensional imaging. To overcome this limitation, we introduce a platform that generates deeply subwavelength PVs through quasi-bound states in the continuum (qBICs) in dielectric metasurfaces. In contrast to existing approaches, the qBIC intrinsically locks the PV to a single OAM and makes it robust against the polarization state of the excitation, including linear, elliptical and circular polarization. We experimentally realize qBIC-driven PVs through the interference of hyperbolic phonon polaritons (HPhPs) in hexagonal boron nitride by exploiting the highly uniform out-of-plane electric fields generated by the photonic qBIC, characterized via scattering scanning near-field optical microscopy. This results in HPhPs with a wavelength of around 30-40 smaller than the incident light, thereby enabling ultra-dense packing of multiple robust PVs with distinct OAM. Our platform brings PVs to the photonic chip scale, enabling applications in structured optical information transfer and communications.

physics.optics↗

arXiv2026

Extreme light confinement mediated by the transverse Kerker effect

Dielectric nanoparticles can be engineered to scatter light predominantly in the transverse direction, a phenomenon known as the transverse Kerker effect. Although complete cancelation of forward scattering from a single object is forbidden by the optical theorem, we show that a single photonic mode can nonetheless realize an ideal transverse Kerker effect. The mode remains dark under normal incidence but evolves into an accidental bound state in the continuum when the nanoparticles are arranged in metasurfaces. This enables a new route to polarization-independent quasi-bound states in the continuum whose quality factors are tunable without symmetry breaking. We experimentally demonstrate our concept in the visible, achieving the first polarization-independent bound state in the continuum without the need for Brillouin-zone folding. Furthermore, we show that our modes maintain large quality factors over a substantially broader region of momentum space than conventional bound states in the continuum. Our results establish a platform for realizing ultranarrow resonances free of the constraints for designs with standard bound states in the continuum.

physics.optics↗

arXiv2025

Integration of 2D Materials in Radial van der Waals Heterostructure Metasurfaces

Two-dimensional semiconductors, such as monolayer transition metal dichalcogenides (TMDC), exhibit strong excitonic transitions at room temperature and offer a unique platform for exploring light-matter interactions in nanoscale photonic systems. In this work, we demonstrate a compact and polarization-invariant photonic metasurface, fabricated from hexagonal boron-nitride (hBN) and based on radial bound states in the continuum (BIC), which are formed by radially distributed pairs of structurally asymmetric resonators. The metasurface employs multiple symmetry-breaking perturbations to support high quality-(Q-)factor resonances within a footprint smaller than 8 x 8 $\mu m^2$ - one-sixth of the area of previous approaches. Compared to established hBN metasurface designs, the radial geometry furthermore achieves significantly higher Q-factors with a reduced footprint. By integrating the hBN photonic structure with a WS$_2$ monolayer, we observe enhanced photoluminescence when its resonance is spectrally aligned with the exciton resonance, accompanied by signatures of discrete momentum-space patterns that identify the orbital-angular-momentum-carrying ring eigenmodes. These features persist over a wide range of excitation powers and show minimal linewidth broadening, indicating robust and spatially modulated exciton-photon coupling. This work establishes a scalable approach for generating hybrid photonic-excitonic states with momentum-space structure, offering new opportunities for exciton localization, valley emission, spatially programmable light-matter interaction in two-dimensional material platforms and compact luminescent devices based on 2D material-integrated metasurfaces.

physics.optics↗

arXiv2025

Accessible, All-Polymer Metasurfaces: Low Effort, High Quality Factor

Optical metasurfaces supporting resonances with high quality factors offer an outstanding platform for applications such as non-linear optics, light guiding, lasing, sensing, light-matter coupling, and quantum optics. However, their experimental realization typically demands elaborate multi-step procedures such as metal or dielectric deposition, lift-off, and reactive ion etching. As a consequence, accessibility, large-scale production and sustainability are constrained by reliance on cost-, time- and labor-intensive facilities. We overcome this fabrication hurdle by repurposing polymethyl methacrylate-which is usually employed as a temporary resist-as the resonator material, thereby eliminating all steps except for spin-coating, exposure and development. Because the low refractive index of the polymer limits effective mode formation, we present a bilayer recipe that enables the convenient fabrication of a freestanding membrane to maximize the index contrast with its surroundings. Since etching induced defects are circumvented, the membrane features high quality nanopatterns. We further examine the suspended membrane with scanning electron microscopy and extract its position-dependent spring constant and pretension with nanoindentation experiments applied by the tip of an atomic force microscope. Our all-polymer metasurface hosting Bound States in the Continuum experimentally delivers high quality factors (up to 523) at visible and near infrared wavelengths, despite the low refractive index of the polymer, and enables straightforward geometry-based tuning of both linewidth and resonance position. We envision this methodology to lay the groundwork for accessible, high performance metasurfaces with unique use cases such as material blending, angled writing and mechanically based resonance tuning.

physics.optics↗

arXiv2025

Topological Control of Polaritonic Flatbands in Anisotropic van der Waals Metasurfaces

Anisotropic van der Waals (vdW) materials exhibit direction-dependent optical and electronic properties, making them valuable for tailoring directional light-matter interactions. Rhenium disulfide (ReS$_2$) stands out for its strong in-plane anisotropy and its thickness-independent direct-bandgap excitons, which can hybridize with light to form exciton-polaritons. In parallel, metasurfaces, engineered arrays of nanoscale subwavelength resonators, can support ultra-sharp photonic modes in the form of quasi-bound states in the continuum (qBICs). Topological transformations of photonic modes can give rise to flatbands, i.e., dispersionless states with quenched kinetic energy and vanishing group velocity. Intrinsic material anisotropy offers an unexplored route to robust far-field flatband formation and control. Here, we demonstrate how structuring an intrinsically anisotropic excitonic material into a resonant metasurface fundamentally transforms its photonic topological features and light-matter coupling behavior, allowing us to drive and topologically control extended far-field flatband formation. To this end, we fabricate C$_4$-symmetric metasurfaces directly from bulk ReS$_2$. The intrinsic anisotropy lifts the initial double degeneracy of the qBIC mode and yields two distinctly polarized resonances. It also reshapes the topological landscape: the integer topological charge of the qBIC mode splits into momentum-separated half-integer singularities, thereby flattening the far-field photonic dispersion. The resulting topologically-controlled photonic flatbands are then tuned in resonance with the linearly polarized excitonic transitions of ReS$_2$, resulting in two distinct, directionally hybridized exciton-polariton flatband regimes. These findings establish anisotropic vdW metasurfaces as a new platform for topologically engineered flatbands and flatband-driven light-matter coupling.

physics.optics↗

arXiv2025

Fabrication Optimization of van der Waals Metasurfaces: Inverse Patterning Boosts Resonance Quality Factor

Van der Waals (vdW) materials have garnered growing interest for use as nanophotonic building blocks that offer precise control over light-matter interaction at the nanoscale, such as optical metasurfaces hosting sharp quasi-bound states in the continuum resonances. However, traditional fabrication strategies often rely on lift-off processes, which inherently introduce imperfections in resonator shape and size distribution, ultimately limiting the resonance performance. Here, an optimized fabrication approach for vdW-metasurfaces is presented that implements inverse patterning of the etching mask, resulting in increased resonator quality solely limited by the resolution of the electron beam lithography resist and etching. Applying this inverse fabrication technique on hexagonal boron nitride (hBN), quality (Q) factors exceeding $10^3$ in the visible spectral range were demonstrated, significantly surpassing previous results shown by lift-off fabricated structures. Additionally, the platforms potential as a biosensor was displayed, achieving competitive sensitivity and figure of merit of 220 in a refractive index sensing experiment. The inverse technique was applied to create chiral metasurfaces from hBN, using a two-height resonator geometry to achieve up to 50 % transmittance selectivity. This inverse lithography technique paves the way towards high-performances vdW-devices with high-Q resonances, establishing hBN as a cornerstone for next-generation nanophotonic and optoelectronic devices.

physics.optics↗

arXiv2025

Spatially Encoded Polaritonic Ultra-Strong Coupling in Gradient Metasurfaces with Epsilon-Near-Zero Modes

We introduce a platform to achieve ultra-strong coupling (USC) between light and matter using widely available materials. USC is a light-matter interaction regime characterized by coupling strengths exceeding 10% of the ground state energy. It gives rise to novel physical phenomena, such as efficient single-photon coupling and quantum gates, with applications in quantum sensing, nonlinear optics, and low-threshold lasing. Although early demonstrations in plasmonic systems have been realized, achieving USC in dielectric platforms, which offer lower losses and high Q-factors, remains challenging due to typically low mode overlap between the photonic field and the material resonance. Here we leverage dielectric dual gradient metasurfaces supporting quasi-bound states in the continuum to spatially encode both the spectral and coupling parameter space and demonstrate USC to an epsilon-near-zero (ENZ) mode in an ultra-thin SiO2 layer. The strong out-of-plane electric fields in our tapered bar structure overlap exceptionally well with those of the ENZ mode, resulting in a normalized coupling strength of 0.101 and a mode splitting equivalent to 20% of the ENZ mode energy; a four- to five-fold increase compared to previous approaches. The strong field confinement of our approach opens new possibilities for compact and scalable polaritonic devices, such as tunable frequency converters and low-energy optical modulators.

physics.optics↗

arXiv2024

Chiral Nonlinear Polaritonics with van der Waals Metasurfaces

In the strong-coupling regime, the interaction between light and matter reaches a hybridization state where the photonic and material components are inseparably linked. Using tailored states of light to break symmetries in such systems can facilitate the development of novel non-equilibrium quantum materials. Chiral optical cavities offer a promising approach for this, enabling either temporal or spatial symmetry-breaking, both of which are unachievable with conventional mirror cavities. For spatial symmetry-breaking, a cavity must discriminate the handedness of circularly polarized light, a functionality uniquely provided by chiral metamaterials. Here, we propose and demonstrate experimentally a chiral transition metal dichalcogenide (TMDC) metasurface with broken out-of-plane symmetry, allowing for the selective formation of self-hybridized exciton-polaritons with specific handedness. Our metasurface maintains maximal chirality for oblique incidence up to 20{\deg}, significantly outperforming all previously known designs, thereby transforming the angle of incidence from a constraint into a new degree of freedom for sub-nanometer-precise tuning of the cavity's resonant wavelength. Moreover, we study the chiral strong-coupling regime in nonlinear experiments and reveal the polariton-driven nature of chiral third-harmonic generation. Our results demonstrate a clear pathway towards van der Waals (vdW) metasurfaces as a novel and potent platform for chiral polaritonics with implications in a wide range of photonics research, such as non-reciprocal photonic devices and valleytronics.

physics.optics↗