Abstract
The silencing of the second harmonic generation process from plasmonic nanostructures corresponds to the limited far-field second harmonic radiation despite the huge fundamental electric field enhancement in the interstice between two plasmonic nanoparticles forming a nanodimer. In this article, we report a comprehensive investigation of this effect using a surface integral equation method. Various geometries are considered, including nanoantennas with cylindrical and rectangular arms as well as nanodimers with surface defects. The existence of the silencing of the second harmonic generation from plasmonic nanogaps is first confirmed, and the problem of the origin of the second harmonic light from these plasmonic nanostructures is addressed in detail. Our results show that the distribution of the second harmonic sources, especially on the arm sides, plays a non-negligible role in the overall second harmonic emission. This contribution is induced by retardation effects at the pump wavelength and results in a dipolar second harmonic emission.
Highlights
Due to their high density of free electrons, plasmonic nanostructures offer the possibility to concentrate light into subwavelength regions [1,2]
This localized surface plasmon resonances (LSPRs) corresponds to the bonding dipolar mode, resulting from the in-phase coupling of the longitudinal dipolar modes supported by each nanorod
This article reports a comprehensive study of the “silencing” effect in the second harmonic generation (SHG) from gold nanoantennas using a surface integral equation method
Summary
Due to their high density of free electrons, plasmonic nanostructures offer the possibility to concentrate light into subwavelength regions [1,2]. The collective oscillations of these electrons in a given plasmonic nanostructure are called localized surface plasmon resonances (LSPRs) [3,4,5]. The high electric field enhancement associated with the optical excitation of such a resonance has been proven to be an important, practical way to control light–matter interaction down to the nanoscale [3,4,5]. To even further enhance this interaction, it was proposed to couple two plasmonic nanostructures by bringing them close to each other, resulting in a nanoantenna made of two arms separated by a gap of a few nanometers [6].
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