Engineering plasmon dispersion relations: hybrid nanoparticle chain-substrate plasmon polaritons

Area of Science:

• Plasmonics
• Nanophotonics
• Condensed Matter Physics

Background:

• Optical excitations in nanoparticle systems are crucial for nanophotonics.
• Understanding plasmon coupling is key to controlling light-matter interactions at the nanoscale.

Purpose of the Study:

• To investigate the nature of optical excitations in silver nanoparticle chains on a metal substrate.
• To explore the tunability of optical properties and group velocity.
• To demonstrate the potential for designing nano-optical devices with tailored transport characteristics.

Main Methods:

• Analysis of dispersion relations for optical excitations.
• Modeling of hybrid plasmon polaritons.
• Calculation of Poynting vectors to determine energy and phase propagation.

Main Results:

• Identified optical excitations as hybrid plasmon polaritons (localized surface plasmons and surface plasmon polaritons).
• Demonstrated strong dependence of optical properties on substrate plasma frequency.
• Showcased engineering of group velocity (high, low, or negative) by tuning plasma frequency.

Conclusions:

• Hybrid plasmon polaritons govern optical excitations in this system.
• Substrate plasma frequency offers a powerful tool for controlling plasmonic modes.
• Results pave the way for designing nano-optical devices with engineered light transport properties, including negative group velocity.