Plasmon‐Induced Disorder Engineering for Robust Optical Sensors

Abstract

Optical metasurfaces address a plethora of applications in planar optics, as they enable precise control of the phase, amplitude, and polarization of light at nanoscale interaction lengths. However, their implementation requires surface nanostructuring, based on complex design and fabrication methods. In addition, exploiting narrow spectral features, e.g., for sensing, is accompanied by high demands in terms of precise post‐process alignments of probing light—impractical for compact optical systems. Here, the realization of plasmonic metasurfaces, based on silver nanoparticles (AgNPs) and using a solution‐based growth method, is demonstrated. The particle growth is mediated by localized surface plasmon resonances. The resulting nanostructures are directly applicable as self‐optimized metasurfaces in optical systems, as their fabrication and probing procedures allow the use of common—photonic and plasmonic—platforms. Information regarding the electromagnetic (EM) environment is stored during the fabrication via distinct particle positions and dimensions. The resulting optical response is inherently sensitive to deviations from this EM environment—enabling high‐performance nanoplasmonic sensing with a maximum discrete Figure of Merit* (FoMmax∗ of 968 without the need for post‐process alignments.

Harnessing Short-Range Surface Plasmons in Planar Silver Films via Disorder-Engineered Metasurfaces

“…However, despite the low Q -factors of the SR-SPPs ranging from Q = 33 to Q = 83 for t m = 20 nm and t m = 40 nm, respectively, the presented approach enables us to obtain very sharp resonances. The sharpness arises due to the delocalized nature of the system response under coherent illumination on large areas (in the range of several tens of mm 2 ) . The results presented in this work thus represent a first step toward the facile utilization of SR-SPPs in planar optical sensing devices with extraordinary performance in detecting surface binding events in the future.…”

“…2 Recently, it has been shown that a disorder-engineered metasurface consisting of silver nanoparticles (AgNPs) in close proximity to a thin silver film can enable high optical sensing performance. 17 Due to the selective scattering mediated by the metasurface, the SPP modes propagating on the silver film create a sharp resonance in the reflection signal, which is highly sensitive to the refractive index of the analyte. The width of this resonance is around 2 orders of magnitude narrower compared to the initial SPP resonance without the metasurface and is largely governed by the divergence of the laser used for fabrication and probing.…”

“…Recently, it has been shown that a disorder-engineered metasurface consisting of silver nanoparticles (AgNPs) in close proximity to a thin silver film can enable high optical sensing performance . Due to the selective scattering mediated by the metasurface, the SPP modes propagating on the silver film create a sharp resonance in the reflection signal, which is highly sensitive to the refractive index of the analyte.…”

High‐Contrast Switching of Light Enabled by Zero Diffraction

“…[ 14,15 ] Metasurfaces built from thin subwavelength structures have drawn attention as an advanced tool to control the properties of light. [ 16–18 ]…”

“…[14,15] Metasurfaces built from thin subwavelength structures have drawn attention as an advanced tool to control the properties of light. [16][17][18] In symmetric waveguide gratings, large sensitivity is reported for odd modes providing a node of minimized interaction with the center grating. [19] The highest sensitivity in waveguide gratings, however, is reported for dielectric bound state in the continuum (BICs) showing zero diffraction to the radiation continuum.…”