Anomalous optical forces on the anisotropic Rayleigh particles

Area of Science:

• Optics and Photonics
• Condensed Matter Physics
• Electromagnetism

Background:

• The behavior of optical forces on small particles is crucial in various applications.
• Rayleigh's law, a well-established principle, describes these forces for isotropic spheres.
• The influence of anisotropy on optical forces requires further investigation.

Purpose of the Study:

• To investigate the optical forces acting on radially anisotropic spheres under plane wave illumination.
• To explore deviations from the conventional Rayleigh's law for anisotropic spheres.
• To understand how anisotropic parameters and resonance affect optical forces.

Main Methods:

• Generalized full-wave scattering theory.
• Maxwell stress tensor integration techniques.
• Analysis of optical forces for various anomalous dependencies (e.g., F~k00a(2), F~k0-2a(0)).

Main Results:

• Optical forces on radially anisotropic spheres do not always follow Rayleigh's law (F~k04a(6)).
• Anomalous force laws (e.g., F~k00a(2), F~k0-2a(0), F~k08a(10)) were observed under specific conditions.
• Optical forces are enhanced at electric dipole resonance and can be tuned by anisotropic parameters.
• Electromagnetic transparency in anisotropic spheres leads to a significant reduction in optical forces.

Conclusions:

• The optical force on anisotropic Rayleigh spheres exhibits complex behavior beyond classical predictions.
• Anisotropy offers a pathway to manipulate optical forces, enabling enhancement or reduction.
• These findings have implications for designing optical systems and manipulating nanoparticles.