Separating and transporting of particles using tightly focused radially polarized Bessel-Gaussian beam with conical phase

The intensity distributions near the focus for radially polarized Bessel-Gaussian beam with conical phase by a high numerical aperture objective are computed based on the vector diffraction theory. Results show that the circular focal spot can be changed from one to two on the focal plane by adjusting the truncation parameter beta. By increasing the phase modulation parameter L, the focal pattern appeared focal shift. According to the intensity distribution, the forces acting on a particle are calculated. The stability of particle trapping is analyzed. It is shown that a tightly focused radially polarized Bessel-Gaussian beam with conical phase is applicable to trapping, separating and transporting of particles.