Polarization-independent dielectric gradient near-perfect absorbers for aqueous mid-infrared molecular sensing

Publikationstyp
Journal Article
Date Issued
2026-12-01
Sprache
English
Author(s)
Yang, Xingye
Jiang, Tao  
Rohrer, Lina 
Biechteler, Jonas 
Tittl, Andreas  
TORE-URI
https://hdl.handle.net/11420/63328
Journal
Npj Nanophotonics  
Volume
3
Issue
1
Article Number
25
Citation
Npj Nanophotonics 3 (1): 25 (2026)
Publisher DOI
10.1038/s44310-026-00121-9
Scopus ID
2-s2.0-105035618378
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.
DDC Class
600: Technology