Silencing the second harmonic generation from plasmonic nanodimers: A comprehensive discussion

Area of Science:

• Plasmonics
• Nonlinear Optics
• Nanophotonics

Background:

• Plasmonic nanostructures exhibit strong local electric field enhancement.
• Second harmonic generation (SHG) is a key nonlinear optical process in nanostructures.
• Limited far-field SHG radiation from plasmonic nanogaps is observed despite intense localized fields.

Purpose of the Study:

• To comprehensively investigate the silencing of SHG in plasmonic nanostructures.
• To understand the origin of second harmonic light emission from nanodimers and nanoantennas.
• To analyze the role of source distribution and retardation effects on SHG.

Main Methods:

• Surface integral equation method.
• Simulation of various geometries: nanoantennas (cylindrical, rectangular arms) and nanodimers with defects.
• Analysis of fundamental field enhancement and SHG source distribution.

Main Results:

• Confirmed the silencing of SHG in plasmonic nanogaps.
• Identified the significant role of second harmonic source distribution, particularly on arm sides.
• Demonstrated that retardation effects at the pump wavelength induce dipolar SHG emission.

Conclusions:

• The silencing of SHG is a complex phenomenon influenced by source distribution and retardation effects.
• Understanding these effects is crucial for optimizing SHG in plasmonic nanostructures.
• Retardation-induced dipolar emission contributes to the overall SHG from these systems.