Rotational properties of micro-slabs driven by linearly-polarized light

International audienceWe study the rotational motion of objects trapped in a focused laser beam (optical tweezers). Micrometer-sized flat slabs are fabricated using two-photon photopolymerization. These objects, trapped by linearly-polarized light, tend to align parallel to the polarization plane. This alignment effect is attributed to the polarization anisotropy resulting from the object shape and we present a simple electromagnetic approach to estimate the resulting optical torque. Micro-rotors of different sizes are studied experimentally. We characterize the behavior of micro-objects when the light polarization is rotated at constant speed. Our theoretical approach gives a good prediction of how the size of micro-objects affects their rotation efficiency