Tailoring optical pulling force on gain coated nanoparticles with nonlocal effective medium theory

Area of Science:

• Plasmonics and Nanophotonics
• Optical Forces
• Metamaterials

Background:

• Understanding optical forces on nanoparticles is crucial for nano-optical manipulation.
• Coated nanoparticles with gain cores and plasmonic shells offer unique optical properties.
• Nonlocal effects in plasmonic materials can significantly alter their response.

Purpose of the Study:

• To investigate the optical scattering force on coated nanoparticles with gain cores and nonlocal plasmonic shells.
• To explore the phenomenon of negative optical force in these nanostructures.
• To analyze the influence of nonlocality on optical force characteristics.

Main Methods:

• Theoretical study of optical scattering force in the long-wavelength limit.
• Application of nonlocal effective medium theory to derive equivalent permittivity.
• Analysis of surface plasmon resonances (symmetric and antisymmetric).
• Investigation of Fano-like resonant scattering phenomena.

Main Results:

• Demonstration of negative optical force near surface plasmon resonances.
• Identification of negative imaginary part of equivalent permittivity as the cause of negative force.
• Observation that nonlocality can shift resonant wavelengths and strengthen negative optical force.
• Discovery of Fano resonance-induced negative optical force.

Conclusions:

• Coated nanoparticles with gain cores and nonlocal plasmonic shells exhibit tunable negative optical forces.
• Nonlocal effects are key to achieving enhanced negative optical forces.
• These findings hold promise for applications in plasmonics, nano-optical manipulation, and optical selection.