Nonlinear Circular Dichroism in Mie-Resonant Nanoparticle Dimers

Area of Science:

• Nonlinear optics
• Plasmonics
• Nanophotonics

Background:

• Dielectric nanoparticles exhibit Mie resonances, enabling light manipulation.
• Coupled nanoparticle systems (dimers) show unique optical properties due to mode hybridization.
• Nonlinear optical phenomena like second-harmonic generation (SHG) are crucial for frequency conversion.

Purpose of the Study:

• To investigate the nonlinear response of a dimer composed of two identical Mie-resonant dielectric nanoparticles.
• To develop a general theory for the hybridization of multipolar modes in such dimers.
• To reveal and enhance nonlinear circular dichroism (CD) in the SHG signal.

Main Methods:

• Theoretical modeling of multipolar mode hybridization in dielectric nanoparticle dimers.
• Numerical simulations of light-matter interactions.
• Experimental validation using AlGaAs dimers on an engineered substrate.

Main Results:

• A general theory for multipolar mode hybridization in dielectric nanoparticle dimers was developed.
• Nonvanishing nonlinear circular dichroism (CD) was observed in the second-harmonic generation (SHG) signal.
• CD enhancement was attributed to multipolar resonances and specific dimer orientation relative to the crystalline lattice.

Conclusions:

• The study demonstrates a pathway to achieve significant nonlinear circular dichroism in dielectric nanoparticle systems.
• Multipolar resonance hybridization offers a powerful mechanism for controlling and enhancing nonlinear optical responses.
• Experimental results validate the theoretical predictions, paving the way for novel nanophotonic devices.