Tailored multipolar optical trapping with higher-order structured light

Structured light illumination opens up opportunities for customized trapping landscapes, unveiling the possibility of gray trapping, especially for larger Mie particles that can excite a higher-order multipolar response. While previous studies have primarily focused on calculations of the gradient force for some exemplary, focused scalar beams, we not only extend these analyses by combining vectorial focusing with generalized Lorenz-Mie theory, but also consider more complex trapping fields.

Motivated by their unique tight focusing behavior, shaping strong transverse intensity gradients and three-dimensional electric field components, we explore higher-order cylindrical scalar and vector beams. We theoretically investigate multipolar trapping of Mie-regime silicon nanospheres in water, calculating the three-dimensional net radiation force and assess local trapping stability through the force Jacobian. Near an octupolar Mie resonance, we predict stable gray trapping with enhanced efficiency for vector beams.