Nonlinear optical response from single spheres coated by a nonlinear monolayer.

Area of Science:

• Nonlinear optics
• Photonics
• Materials science

Background:

• Second-order nonlinear optical phenomena are crucial for frequency conversion.
• Studying isolated nanoparticles allows for precise characterization of nonlinear optical responses.
• Traditional theories like Rayleigh scattering often fail for larger particles.

Purpose of the Study:

• To investigate the second-order nonlinear optical response of single, isolated core-shell spheres.
• To compare experimental results with theoretical predictions from nonlinear Rayleigh and Mie scattering theories.
• To demonstrate the applicability of nonlinear Mie theory for larger nanoparticles.

Main Methods:

• Fabrication of single isolated spheres with a centrosymmetric core and a nonlinear shell.
• Utilizing optical trapping to isolate individual spheres for measurement.
• Measuring the second-harmonic generation (SHG) efficiency of the trapped spheres.

Main Results:

• Successfully detected the second-order nonlinear response from single, isolated core-shell spheres.
• Observed significant deviations in second-harmonic efficiency for large size parameter spheres compared to nonlinear Rayleigh scattering predictions.
• Experimental results showed excellent agreement with the exact nonlinear Mie scattering theory.

Conclusions:

• Nonlinear Mie scattering theory accurately describes the second-order nonlinear optical response of larger core-shell nanoparticles.
• Optical trapping is an effective technique for studying individual nonlinear optical elements.
• This work advances the understanding of nonlinear light-matter interactions in structured nanoparticles.