Optical forces on microparticles in an evanescent laser field

Area of Science:

• Optics and Photonics
• Surface Physics
• Computational Physics

Background:

• Evanescent waves generated by total internal reflection are crucial in near-field optics.
• Understanding radiation forces on particles near interfaces is key for optical manipulation and sensing.
• Previous studies have explored optical forces but lacked precise theoretical models for near-interface effects.

Purpose of the Study:

• To develop an exact theoretical framework for calculating radiation forces on microsized particles interacting with evanescent waves.
• To analyze the influence of particle proximity to a dielectric interface on these forces.
• To interpret existing experimental data and propose novel optical effects.

Main Methods:

• Exact calculation of radiation forces using electromagnetic theory.
• Numerical simulation incorporating multiple light scattering between the particle and the flat dielectric surface.
• Theoretical modeling of light-matter interaction in the near-field regime.

Main Results:

• The theory accurately predicts radiation forces on particles influenced by evanescent waves near a flat substrate.
• The proximity of the interface significantly modifies the optical forces, as shown by numerical simulations.
• The model provides a clear interpretation of experimental observations by Kawata and Sugiura.

Conclusions:

• The presented theory offers a robust method for understanding and quantifying optical forces in near-field conditions.
• This work validates theoretical predictions against experimental data, enhancing confidence in the model.
• The developed framework opens avenues for predicting and designing new optical phenomena and applications.