Broadband Tip-Enhanced Nonlinear Optical Response in a Plasmonic Nanocavity

Area of Science:

• Plasmonics
• Nonlinear Optics
• Nanophotonics

Background:

• Plasmonic nanocavities are crucial for enhancing light-matter interactions.
• Nonlinear optical effects, such as second harmonic generation, are fundamental in photonics.
• Tip-enhancement offers a pathway to boost nonlinear optical responses.

Purpose of the Study:

• To investigate the broad nonlinear optical response in a tip-substrate plasmonic nanocavity.
• To understand the influence of tip geometry on nonlinear optical effects.
• To explore the wavelength dependency of tip-enhanced nonlinear optical phenomena.

Main Methods:

• Utilized wavelength-tunable femtosecond lasers to probe nonlinear optical responses.
• Focused on near-field second harmonic generation.
• Analyzed the impact of tip apex sharpness and tip shaft geometry.

Main Results:

• Demonstrated significantly broad nonlinear optical response from visible to infrared wavelengths.
• Showcased efficient tip-enhancement of nonlinear optical effects.
• Identified dual plasmonic modes (nonlocal and localized) contributing to enhanced second harmonic generation.

Conclusions:

• The study provides a new foundation for understanding and manipulating nonlinear optical phenomena in plasmonic nanocavities.
• Tip geometry plays a critical role in achieving broadband nonlinear optical enhancement.
• Simultaneous excitation of nonlocal and localized plasmonic modes leads to strong and broad second harmonic generation.