arXiv subjects

Johannes Bürger

Publications and source records attributed to Johannes Bürger.

7 recordsLinked to original sources

arXiv2026

Very strong light-matter coupling in patterned GaAs heterostructures

The very strong light-matter coupling regime enables the non-perturbative modification of matter properties via light. Using a patterned GaAs/AlGaAs waveguide with twelve wide quantum wells, we demonstrate hybridization of heavy- and light-hole excitons within a single polariton state and show that, at finite magnetic field, the presence of the light-hole exciton suppresses coupling to the heavy-hole Rydberg excitons and unbound scattering states. We develop a fully microscopic theory that accounts for the combined effects of the magnetic field and light-matter coupling on the excitons, providing an accurate description of the experimental results beyond a perturbative coupled-oscillator framework. This identifies quantum well width as a key control parameter for engineering the light-induced hybridization of matter wave functions in polaritons, which, in turn, can play a crucial role in the optical non-linearities.

cond-mat.mes-hall↗

arXiv2026

Magnetic-field driven hybridization of heavy- and light-hole Rydberg excitons in GaAs quantum wells

We present a combined theoretical and experimental study of ground and excited Rydberg exciton states in wide GaAs quantum wells exposed to a magnetic field in the Faraday geometry. We employ a multiband exciton model based on the Luttinger Hamiltonian, which captures valence-band mixing between heavy- and light-hole states induced by both the quantum well confinement and the magnetic field, and we develop an efficient numerical approach to solve for both ground- and excited-state excitons. The method treats Coulomb interactions, magnetic confinement, and band mixing on an equal footing, enabling a systematic characterization of exciton energies, oscillator strengths, and orbital composition. We show that band hybridization increases with magnetic field and is significantly more pronounced for higher excited states, where it sets in at lower fields and strongly modifies their properties. The theoretical predictions are validated by polarization-resolved magneto-reflectance measurements up to 9 T on GaAs/Al$_{0.4}$Ga$_{0.6}$As quantum wells of 20 nm width. We find excellent agreement for both the diamagnetic shift and Zeeman splitting of the ground state and the first four Rydberg excitons. Our results demonstrate that valence-band mixing plays a crucial role in determining the magnetic-field dependence of excited exciton states and must be properly included for a quantitative description of magneto-excitons in wide GaAs quantum wells.

cond-mat.mes-hall↗

arXiv2026

Exciton-Tunable Phase Control and Superstrong Coupling Through Multimode Polariton Engineering in Planar Waveguides

Strong light-matter coupling in optical waveguides provides a versatile platform for engineering hybrid polaritonic modes and their dispersion. Here we investigate multimode exciton-photon coupling in visible semiconductor waveguides supporting several transverse electric modes. Using rigorous coupled-wave analysis combined with a coupled-oscillator model, we show that the photonic band structure can be engineered across a range of regimes, from conventional multimode strong coupling to the superstrong coupling regime, where the Rabi splitting becomes comparable to the spacing between adjacent photonic modes. In the latter regime, hybridization between orthogonal electromagnetic modes is enabled by restricting the active material to a subregion of the mode volume where the photonic modes exhibit strong mutual overlap. This breaking of the orthogonality leads to polaritonic branches whose composition can be tuned among several photonic modes and the exciton. We demonstrate that small shifts of the exciton resonance produce pronounced changes in the propagation constants of different polariton branches, enabling exciton-controlled phase modulation through modal interference and, in the superstrong coupling regime, direct modal switching across a continuous S-shaped dispersion. The resulting figures of merit predict $π$ phase shifts for exciton energy shifts of only a few meV over propagation lengths of tens of micrometers, while larger shifts are still required for mode switching. These results establish multimode waveguide polaritons as a versatile platform spanning multiple coupling regimes, for compact phase and intensity control in integrated photonic architectures.

physics.optics↗

arXiv2025

On-chip twisted hollow-core light cages: enhancing planar photonics with 3D nanoprinting

Twisted optical fibers are a promising platform for manipulating circularly polarized light and orbital angular momentum beams for applications such as nonlinear frequency conversion, optical communication, or chiral sensing. However, integration into chip-scale technology is challenging because twisted fibers are incompatible with planar photonics and the achieved twist rates are limited. Here, we address these challenges by introducing the concept of 3D-nanoprinted on-chip twisted hollow-core light cages. We show theoretically and experimentally that geometrical twisting of light cages forces the fundamental core mode of a given handedness to couple with selected higher-order core modes, resulting in strong circular dichroism (CD). These chiral resonances result from the angular momentum harmonics of the fundamental mode, allowing us to predict their spectral locations and the occurrence of circular birefringence. Twisted light cages enable very high twist rates and CD, exceeding those of twisted hollow-core fibers by more than two orders of magnitude (twist period: 90 $μ$m, CD: 0.8 dB/mm). Moreover, the unique cage design provides lateral access to the central core region, enabling future applications in chiral spectroscopy. Therefore, the presented concept opens a path for translating twisted fiber research to on-chip technology, resulting in a new platform for integrated chiral photonics.

physics.optics↗

arXiv2025

Trajectory Planning for Automated Driving using Target Funnels

Self-driving vehicles rely on sensory input to monitor their surroundings and continuously adapt to the most likely future road course. Predictive trajectory planning is based on snapshots of the (uncertain) road course as a key input. Under noisy perception data, estimates of the road course can vary significantly, leading to indecisive and erratic steering behavior. To overcome this issue, this paper introduces a predictive trajectory planning algorithm with a novel objective function: instead of targeting a single reference trajectory based on the most likely road course, tracking a series of target reference sets, called a target funnel, is considered. The proposed planning algorithm integrates probabilistic information about the road course, and thus implicitly considers regular updates to road perception. Our solution is assessed in a case study using real driving data collected from a prototype vehicle. The results demonstrate that the algorithm maintains tracking accuracy and substantially reduces undesirable steering commands in the presence of noisy road perception, achieving a 56% reduction in input costs compared to a certainty equivalent formulation.

cs.RO↗

arXiv2024

Impact of coordinate frames on mode formation in twisted waveguides

Off-axis twisted waveguides possess unique optical properties such as circular and orbital angular momentum (OAM) birefringence, setting them apart from their straight counterparts. Analyzing mode formation in such helical waveguides relies on the use of specific coordinate frames that follow the twist of the structure, making the waveguide invariant along one of the new coordinates. In this study, the differences between modes forming in high-contrast off-axis twisted waveguides defined in the three most important coordinate systems - the Frenet-Serret, the helicoidal, or the Overfelt frame - are investigated through numerical simulations. We explore modal characteristics up to high twist rates (pitch: 50 $μ$m) and clarify a transformation allowing to map the modal fields and the effective index back to the laboratory frame. In case the waveguide is single-mode, the fundamental modes of the three types of waveguides show significant differences in terms of birefringence, propagation loss, and polarization. Conversely, the modal characteristics of the investigated waveguides are comparable in the multimode domain. Furthermore, our study examines the impact of twisting on spatial mode properties with the results suggesting a potential influence of the photonic spin Hall and orbital Hall effects. Additionally, modes of single-mode helical waveguides were found to exhibit superchiral fields on their surfaces. Implementation approaches such as 3D-nanoprinting or fiber-preform twisting open the doors to potential applications of such highly twisted waveguides, including chip-integrated devices for broadband spin- and OAM-preserving optical signal transport, as well as applications in chiral spectroscopy or nonlinear frequency conversion.

physics.optics↗

arXiv2022

Unlocking the out-of-plane dimension for photonic bound states in the continuum to achieve maximum optical chirality

The realization of lossless metasurfaces with true chirality crucially requires the fabrication of three-dimensional structures, constraining their feasibility for experiments and hampering practical implementations. Even though the three-dimensional assembly of metallic nanostructures has been demonstrated previously, the resulting plasmonic resonances suffer from high intrinsic and radiative losses. The concept of photonic bound states in the continuum (BICs) is instrumental for tailoring radiative losses in diverse geometries, especially when implemented using lossless dielectrics, but applications have so far been limited to planar and intrinsically achiral structures. Here, we introduce a novel nanofabrication approach to unlock the height of generally flat all-dielectric metasurfaces as an accessible parameter for efficient resonance and functionality control. In particular, we realize out-of-plane symmetry breaking in quasi-BIC metasurfaces and leverage this design degree of freedom to demonstrate, for the first time, an optical all-dielectric quasi-BIC metasurface with maximum intrinsic chirality that responds selectively to light of a particular circular polarization depending on the structural handedness. Our experimental results not only open a new paradigm for all-dielectric BICs and chiral nanophotonics but also promise advances in the realization of efficient generation of optical angular momentum, holographic metasurfaces, and parity-time symmetry-broken optical systems.

physics.optics↗