Gradient High‐Q Dielectric Metasurfaces for Broadband Sensing and Control of Vibrational Light‐Matter Coupling

• Published in: Advanced materials (Weinheim) Vol. 36; no. 25; pp. e2314279 - n/a
• Main Authors: Richter, Felix Ulrich, Sinev, Ivan, Zhou, Senlu, Leitis, Aleksandrs, Oh, Sang‐Hyun, Tseng, Ming Lun, Kivshar, Yuri, Altug, Hatice
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01-06-2024
• Subjects: Absorption spectroscopy; Band spectra; Biosensing; bound states in the continuum; Broadband; broadband metasurface; dielectric metasurfaces; high‐Q resonances; Infrared absorption; Metasurfaces; Planar structures; Resonance; Spectral bands; surface‐enhanced infrared absorption spectroscopy (SEIRA); high‐Q resonances; bound states in the continuum; surface‐enhanced infrared absorption spectroscopy (SEIRA); broadband metasurface; dielectric metasurfaces; Biosensing
• ISSN: 0935-9648; 1521-4095; 1521-4095
• DOI: 10.1002/adma.202314279

Surface‐enhanced infrared absorption spectroscopy (SEIRA) has emerged as a powerful technique for ultrasensitive chemical‐specific analysis. SEIRA can be realized by employing metasurfaces that can enhance light‐matter interactions in the spectral bands of molecular vibrations. Increasing sample complexity emphasizes the need for metasurfaces that can operate simultaneously at different spectral bands, both accessing rich spectral information over a broad band, and resolving subtle differences in the absorption fingerprints through narrow‐band resonances. Here, a novel concept of resonance‐gradient metasurfaces is introduced, where the required spectral selectivity is achieved via local high‐quality‐factor (high‐Q) resonances, while the continuous coverage of a broad band is enabled by the gradual adjustment of the unit‐cell dimensions along the planar structure. The highly tailorable design of the gradient metasurfaces provides flexibility for shaping the spectral sampling density to match the relevant bands of target analytes while keeping a compact device footprint. The versatility of the gradient metasurfaces is demonstrated through several sensing scenarios, including polymer mixture deconvolution, detecting a multistep bioassay, and identification of the onset of vibrational strong coupling regime. The proposed gradient‐resonance platform significantly contributes to the rapidly evolving landscape of nonlocal metasurfaces, enabling applications in molecular detection and analysis of fundamental light‐matter interaction phenomena.
Mid‐infrared all‐dielectric gradient metasurfaces, realized by gradually varying unit cell parameters along the structure, provide continuous tuning of high‐Q resonances over an ultra‐broad spectral range in a compact device footprint. The unmatched flexibility of such metasurfaces for SEIRA applications, including polymer mixture deconvolution, sensitive broadband biomolecule detection, and exploring the onset of vibrational strong coupling are demonstrated.