Settings

Now showing1 - 4 of 4
  • Some of the metrics are blocked by your 
    consent settings
    Item type:Publication, Access status: without files ,
    Polarization-independent dielectric gradient near-perfect absorbers for aqueous mid-infrared molecular sensing
    (2026-12-01)
    Yang, Xingye
    ;
    Jiang, Tao
    ;
    Rohrer, Lina
    ;
    Biechteler, Jonas
    ;
    Tittl, Andreas
    Mid-infrared molecular sensing offers molecule-specific vibrational fingerprints, yet practical implementation with nanophotonic platforms is challenged by system complexity and strong signal damping in aqueous environments. Dielectric metasurfaces overcome ohmic losses and local heating constraints of metallic resonators and can support high-quality-factor resonances with spectral selectivity, suitable for image-based spectrometer-less sensing. However, their spatially extended near-fields typically render them susceptible to environmental absorption, preventing operation in water. We demonstrate a compact dielectric perfect-absorber metasurface combining C<inf>4</inf>-symmetric quasi-bound states in the continuum (qBICs) with a dual-gradient architecture. The C<inf>4</inf>-symmetric unit cells ensure polarization-independent resonances, enabling efficient utilization of incident light under arbitrary polarization states. The gradient architecture independently controls radiative loss and resonance wavelength, allowing distinct coupling regimes within one metasurface while achieving high absorbance (>0.8). We demonstrate poly(methyl methacrylate) sensing in air with ~20% absorbance envelope modulation under arbitrary polarization. Furthermore, we introduce a sensing configuration utilizing a 700 nm residual thin-water film that preserves qBIC (absorbance ~0.5) near the prominent water absorption peak. This enables the first demonstration of dielectric metasurface-based mid-infrared molecular sensing under a water background, achieving >30% absorbance envelope modulation. This platform extends the utility of dielectric metasurfaces to aqueous environments and supports versatile, spectrometer-less sensing schemes.
    Publicationtype: Journal Article
      40
  • Some of the metrics are blocked by your 
    consent settings
    Item type:Publication, Access status: without files ,
    A comparative analysis of plasmonic and dielectric metasurface sensing platforms powered by bound states in the continuum
    (2025-08-28)
    Jiang, Tao
    ;
    Bhattacharya, Angana
    ;
    Barkey, Martin
    ;
    Aigner, Andreas
    ;
    Rohrer, Lina
    Nanophotonic platforms based on surface-enhanced infrared absorbance spectroscopy (SEIRAS) have emerged as an effective tool for molecular detection. Sensitive nanophotonic sensors with robust resonant modes and amplified electromagnetic near fields are essential for spectroscopy, especially in lossy environments. Metasurfaces driven by bound state in the continuum (BICs) have unlocked a powerful platform for molecular detection due to their exceptional spectral selectivity. While plasmonic BIC metasurfaces are preferred for molecular spectroscopy due to their high surface fields, enhancing the interaction with analytes, dielectric BICs have become popular due to their high-quality factors and, thus, high sensitivity. However, their sensing performance has largely been demonstrated in air, neglecting the intrinsic infrared (IR) losses found in common solvents. This study evaluates the suitability of plasmonic versus dielectric platforms for in situ molecular spectroscopy. Here, the sensing performance of plasmonic (gold) and dielectric (silicon) metasurfaces is assessed across liquid environments with varying losses resembling typical solvents. The results show that dielectric metasurfaces excel in dry conditions, while plasmonic BIC metasurfaces outperform them in lossy solvents, with a distinct crossover point where both show similar performance. The results provide a framework for selecting the optimal metasurface material platform for SEIRAS studies based on environmental conditions.
    Publicationtype: Journal Article
      13
  • Some of the metrics are blocked by your 
    consent settings
    Item type:Publication, Access status: without files ,
    Polarization-independent metasurfaces based on bound states in the continuum with high Q-factor and resonance modulation
    (Optica Publishing Group, 2025-04-01)
    Yang, Xingye
    ;
    Antonov, Alexander
    ;
    Aigner, Andreas
    ;
    Weber, Thomas
    ;
    Lee, Yohan
    Metasurfaces offer a powerful platform for effective light manipulation, which is crucial for advanced optical technologies. While designs of polarization-independent structures have reduced the need for polarized illumination, they are often limited by either low Q factors or low resonance modulation. Here, we design and experimentally demonstrate a metasurface with polarization-independent quasi-bound state in the continuum (quasi-BIC), where the unit cell consists of four silicon squares arranged in a two-dimensional array and the resonance properties can be controlled by adjusting the edge length difference between different squares. Our metasurface experimentally achieves a Q factor of approximately 100 and a resonance modulation of around 50%. This work addresses a common limitation in previous designs, which either achieved high Q factors exceeding 200 with a resonance modulation of less than 10%, leading to challenging signal-to-noise ratio requirements, or achieved strong resonance modulation with Q factors of only around 10, limiting light confinement and fine-tuning capabilities. In contrast, our metasurface ensures that the polarization-independent signal is sharp and distinct within the system, reducing the demands on signal-to-noise ratio and improving robustness. Experiments show the consistent performance across different polarization angles. This work contributes to the development of versatile optical devices, enhancing the potential for the practical application of BIC-based designs in areas such as optical filtering and sensing.
    Publicationtype: Journal Article
      9
  • Some of the metrics are blocked by your 
    consent settings
    Item type:Publication, Access status: with files ,
    Untersuchung nichtlinearer Schiffsdynamik mit Auftreten von Instabilität und Chaos an Beispielen aus der Offshoretechnik
    (1990)
    Jiang, Tao
    Dynamic behavior of an SPM-tanker, a moored shear-leg crane ship, and a moored barge was numerically investigated using mathematical models that include significant nonlinearities. Static and dynamic bifurcations of the equilibrium of the tanker moored in a constant current were identified by locallinear stability analysis in parameter space. Global nonlinear simulations showed that tanker motions in the autonomous mode were characterized by large-amplitude, long-period self-sustained oscillations for the unstable cases. When additionally subjected to a steady wind or periodic waves, tanker motion response became chaotic. In these cases, extreme sensitivity to initial conditions was verified. Suitable measures were found to stabilize the tanker equilibrium and its motion. For the crane ship in regular waves period multiplication and chaotic behavior were determined using Fourier analysis. For the moored barge in regular waves coexistence of two different attractors was demonstrated with Poincare maps. Chaotic behavior of the moored barge in periodic wave groups was verified by a positive Lyapunov exponent and a fractal Lyapunov dimension.
    Publicationtype: Technical Report
      573  976