Publication

Insights into second-harmonic generation mechanisms in plasmonic nanostructures: Interplay between surface and bulk contributions

2026

Abstract

The origin of second-harmonic generation (SHG) in centrosymmetric materials, such as plasmonic metals, remains a subject of long-standing debate. In this work, the relative roles of local surface- and nonlocal bulk-induced nonlinear sources in the SHG of gold nanostructures are investigated using full-wave simulations and experimental SHG microscopy. The transition from the dipolar to the quadrupolar regime is studied using multipolar decompositions. SHG measurements of fabricated nanocylinders support the simulation results, indicating the increasing role of bulk nonlinearities in high-aspect ratio structures. Far-field scattering diagrams suggest that different SHG sources may be distinguished through directional emission. This study provides a comprehensive framework for understanding and dissecting the microscopic origins of SHG in plasmonic systems.

Official source

https://infoscience.epfl.ch/entities/publication/7ac17cfb-5049-41d1-a521-14ff0a4c0243

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2026

Abstract

Official source

https://infoscience.epfl.ch/entities/publication/7ac17cfb-5049-41d1-a521-14ff0a4c0243

About this result

Related concepts (32)

Second-harmonic generation

Second-harmonic generation (SHG, also called frequency doubling) is a nonlinear optical process in which two photons with the same frequency interact with a nonlinear material, are "combined", and generate a new photon with twice the energy of the initial photons (equivalently, twice the frequency and half the wavelength), that conserves the coherence of the excitation. It is a special case of sum-frequency generation (2 photons), and more generally of harmonic generation.

Nonlinear optics

Nonlinear optics (NLO) is the branch of optics that describes the behaviour of light in nonlinear media, that is, media in which the polarization density P responds non-linearly to the electric field E of the light. The non-linearity is typically observed only at very high light intensities (when the electric field of the light is >108 V/m and thus comparable to the atomic electric field of ~1011 V/m) such as those provided by lasers. Above the Schwinger limit, the vacuum itself is expected to become nonlinear.

Plasmonic metamaterial

A plasmonic metamaterial is a metamaterial that uses surface plasmons to achieve optical properties not seen in nature. Plasmons are produced from the interaction of light with metal-dielectric materials. Under specific conditions, the incident light couples with the surface plasmons to create self-sustaining, propagating electromagnetic waves known as surface plasmon polaritons (SPPs). Once launched, the SPPs ripple along the metal-dielectric interface. Compared with the incident light, the SPPs can be much shorter in wavelength.

Related publications (26)

Insights into second-harmonic generation mechanisms in plasmonic nanostructures: Interplay between surface and bulk contributions

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