Recent optical trapping setups have been utilized to obtain a whole optical force profile curve as a function of the transverse and longitudinal displacement of the beam centre with respect to the coordinate of a microsphere. These experimental results allow to embrace the problem of the proper evaluation of optical forces, which is one of our research line along with our collaborators.
Proposed theories delimit two regimes, Rayleigh and Geometrical Optics, which both imply not having the microsphere of the same order of wavelength where most of the trapping experiments are performed. To circumvent this problem, the Generalized Lorenz-Mie Theory (GLMT) is utilized to describe a trapped sphere of arbitrary dimensions under a focused beam. For objectives with high numerical aperture, in the focal region diffraction rings are present, and might extend over the microsphere bodies. Polarization is also of concern since an incident linear polarized field in the focal region has all non-zero polarization components, along obviously with spherical aberrations due to the refractive index mismatch at the dielectric interface for immersion objectives. Previous research addressed these issues to provide an exact analytical solution to the trapping of an arbitrary sphere by an arbitrary beam.

 

 

For more information, please contact: Dr. Antonio A. R. Neves ( This e-mail address is being protected from spam bots, you need JavaScript enabled to view it )