Resolving plasmon-mediated high-order multiphoton excitation pathways in dolmen nanostructures using ultrafast...

Area of Science:

• Plasmonics
• Nanophotonics
• Nonlinear Optics

Background:

• Multiphoton excitation is crucial for advanced optical applications.
• Understanding plasmon-mediated excitation in nanostructures is key to controlling light-matter interactions.
• Dolmen structures offer unique plasmonic properties for tailored excitation.

Purpose of the Study:

• To describe multiphoton excitation pathways in plasmonic nanorod assemblies.
• To investigate plasmon-mediated three-photon excitation in gold nanorod dolmen structures.
• To correlate high-order plasmon excitation with nonlinear optical signals.

Main Methods:

• Directed assembly of three gold nanorods into dolmen structures.
• Resonant excitation of hybrid plasmon modes using an 800-nm ultrafast laser.
• Sub-cycle time-resolved interferometric detection of nonlinear emission.
• Polarization-dependent excitation to distinguish resonant and non-resonant responses.

Main Results:

• Plasmon-mediated three-photon excitation was successfully resolved in dolmen structures.
• Excitation was found to be structure- and mode-selective, dependent on resonant hybrid modes.
• Non-resonant polarization configurations did not yield third-order responses.
• Non-equilibrium electron distributions were generated through selective excitation.

Conclusions:

• Nonlinear optical interferometry and Fourier analysis are powerful tools for identifying plasmon-mediated processes.
• Structure- and mode-selective excitation is critical for accessing specific high-order multiphoton pathways.
• This work advances the understanding of nonlinear optical phenomena in plasmonic metamaterials.