Single particle light scattering from beams with OAM: measurements and comparison with an angular decomposition based model.

We present experimental results and validating computations of scattering from spherical particles using laser beams with orbital angular momentum (OAM). The measurements are conducted on a single particle translated in a quadrupole trap. We decompose the input field into an ensemble of plane waves via the angular spectrum decomposition method. The scattered field due to each plane wave component is calculated and coherently summed up to yield the total scattering field. We measure the angle-resolved scattering as the particles transit the toroidal-shaped beam. We find that the scattering of light from a single particle within the annulus exhibits scattering that is similar to scattering from a Gaussian beam but shifted in opposite direction on the top and bottom parts of the annulus of the beam. These shifts increase with higher-order modes and shift directions with polarity. The scattering at the center of the toroid is shown to exhibit a minimum at 0°, and the maxima are shown to be at larger angles, increasing with mode order and deviating from the Gaussian scattering pattern. To our knowledge, these are the first angle-resolved single particle scattering measurements under OAM illumination, and our computational results corroborate the measurements.