Optical Trapping and the Momentum of Light

The explanation talks about the wave-particle duality, but I think that’s a distraction. This is a dipole force phenomenon; the beam’s intensity is greatest at the center, and where the focal point occurs, as shown in the drawing at the end of the post. This gives rise to a gradient in the electric field. If you put a dielectric particle in this region, it will feel a force in the direction of the field maximum, or toward the highest intensity of light.