Plasmonic Absorption and Sensing Mechanisms

Plasmonic absorption and sensing exploit collective oscillations of free electrons at metal–dielectric interfaces to concentrate and manipulate light at the nanoscale. When incident radiation couples to surface plasmon polaritons or to localized surface plasmon resonances in metallic nanostructures, strong field enhancements and narrow absorption features emerge. By engineering geometry, material composition and arrangement, one can tailor resonance wavelength, bandwidth and angular or polarisation sensitivity. These characteristics underlie perfect absorbers that achieve near-unity absorption over narrow or multiple spectral bands, and refractive-index sensors whose resonance shifts report on local environmental changes. Such platforms find applications in biosensing, chemical detection, photodetection, imaging and thermal emission, offering compact, label-free and real-time monitoring capabilities.

Research from Nature Portfolio

Recent studies have introduced multiplexed dielectric-grating structures integrated with waveguide layers to achieve multi-band optical filtering and refractive-index sensing in both transverse-electric and transverse-magnetic polarisation. By selectively exciting hybrid surface-plasmon and waveguide modes, these designs deliver spectral shifts of over 110 nm per refractive-index unit with figures of merit exceeding 25 RIU⁻¹, enabling simultaneous detection of multiple analytes across a broad spectral range. In addition, all-metal plasmonic absorbers featuring subwavelength vertical gaps have attained ultra-narrow absorption bandwidths below 8 nm, polarisation-insensitive absorptivity above 99 %, and quality factors exceeding 100. The intense near-field confinement of these gap modes drives field enhancements that directly correlate with perfect absorption, yielding refractive-index sensitivities of nearly 900 nm/RIU and figures of merit above 100 RIU⁻¹.

Plasmonic Absorption and Sensing Mechanisms publication trend

The graph below shows the total number of articles in plasmonic absorption and sensing mechanisms across all publications each year (not limited to Nature Index journals).

Technical terms

Localized surface plasmon resonance (LSPR): Collective oscillation of conduction electrons confined to metallic nanoparticles or nanostructures, producing strong, wavelength-specific field enhancement.

Surface plasmon polariton (SPP): Electromagnetic wave that propagates along a metal–dielectric interface, tightly bound to the surface by coupling to free-electron oscillations.

Perfect absorber: Nanostructured system engineered to eliminate reflection and transmission at resonance, achieving near-unity absorption in a targeted spectral region.

Refractive-index sensitivity: Wavelength shift of a plasmonic resonance per unit change in the surrounding medium’s refractive index, typically expressed in nm/RIU (refractive-index unit).

Figure of merit (FOM): Ratio of refractive-index sensitivity to resonance linewidth, indicating sensor resolution and performance.

Quality factor (Q): Dimensionless parameter equal to resonance wavelength divided by its full-width at half-maximum, measuring spectral sharpness.

References

1. Multiplexed rectangular dielectric gratings with multiple narrow-band refractive index filtering and sensing. Scientific Reports (2024).
2. Design and analysis of quad-band polarization-insensitive infrared perfect metamaterial absorber with a wide-incident angle. Optical and Quantum Electronics (2023).
3. Infrared Plasmonic Refractive Index Sensor with Ultra-High Figure of Merit Based on the Optimized All-Metal Grating. Discover Nano (2017).