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Second Harmonic Spectroscopy of Surface Lattice Resonances
David C Hooper1, Christian Kuppe1, Danqing Wang
1Centre for Photonics and Photonic Materials and Centre for Nanoscience and Nanotechnology, Department of Physics , University of Bath , Claverton Down , Bath BA2 4JY , U.K.
Nano Letters
|December 12, 2018
Summary
Surface lattice resonances (SLRs) in metal nanoparticle arrays show promise for sensing. Second harmonic generation (SHG) spectroscopy significantly enhances SLR signals, improving sensitivity for chemical and biomolecular detection.
Area of Science:
- Plasmonics
- Nanophotonics
- Spectroscopy
Background:
- Surface lattice resonances (SLRs) in metal nanoparticle arrays offer high figures of merit for chemical and biomolecular sensing.
- SLRs exhibit sensitivity to refractive index changes at both the nanoparticle surface and in the interstitial volume.
- Second harmonic generation (SHG) spectroscopy possesses intrinsic surface-sensitivity and electric field dependence, potentially enhancing SLR sensitivities.
Purpose of the Study:
- To investigate the enhancement of surface lattice resonances (SLRs) using second harmonic generation (SHG) spectroscopy in plasmonic nanoparticle arrays.
- To demonstrate the potential of SHG spectroscopy for improved surface and bulk sensitivity in sensing applications.
- To explore the characteristics and origins of SHG resonances in relation to SLRs.
Main Methods:
- Fabrication and characterization of metal nanoparticle arrays.
- Utilizing second harmonic generation (SHG) spectroscopy to probe SLRs.
- Systematic variation of experimental parameters including fundamental wavelength, angle of incidence, nanoparticle material, and lattice constant.
Main Results:
- SHG signals were significantly amplified (up to 450 times) due to the presence of SLRs.
- Observed very narrow resonances in SHG intensity with a full width at half maximum (fwhm) of approximately 5 nm.
- Demonstrated high sensitivity of SHG resonances to SLRs by tuning various array and experimental parameters.
- Identified an electric dipole-forbidden SHG resonance (10 nm fwhm) attributed to higher-order multipoles enhanced by SLR near-fields.
Conclusions:
- SHG spectroscopy effectively enhances SLR signals in metal nanoparticle arrays, leading to significant improvements in sensitivity.
- The narrow SHG resonances are highly sensitive to SLR properties, offering precise detection capabilities.
- The identification of multipolar SHG resonances opens new possibilities for advanced sensing mechanisms.
- SHG spectroscopy of SLRs presents a promising platform for highly sensitive chemical and biomolecular sensing.
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