Optical particle trapping with focused pseudo-Schell model beams

Based on pseudo-modal expansions of partially coherent beams, an analytical expression for the cross-spectral density function of pseudo-Schell model beams through an ABCD optical system is derived. The intensity distributions calculated using analytical method show excellent agreement with those by numerical integration. The radiation forces of focused pseudo-Schell model beams on Rayleigh dielectric particles are investigated. It is found that focused Gaussian pseudo-Schell model (GPSM) beams can stably trap high-refractive-index particles at the focus, while focused vortex Gaussian pseudo-Schell model (VGPSM) beams can trap low- and high-refractive-index particles simultaneously. Compared with focused Gaussian Schell-model (GSM) beams, focused GPSM beams generate stronger radiation forces under identical beam parameters, making them more effective for particle trapping. The vortex Gaussian Schell-model (VGSM) beams with a large coherence length exhibit a particle trapping capability comparable to that of VGPSM beam. The pseudo-modal expansion method of pseudo-Schell model beams through an ABCD optical system reduces the dimensionality of the integration and facilitates the synthesis and analysis of such beams in propagation. The findings provide a theoretical basis for the use of both GPSM beams and VGPSM beams in particle trapping.