Optical forces in twisted split-ring-resonator dimer stereometamaterials.

We numerically investigate the optical forces in stereometamaterials composed of two-dimensional arrays of two spatially stacked split ring resonators with a twisted angle. At the hybridized magnetic resonances, we obtain both attractive and repulsive relative optical forces, which can be further exploited to control the separation between the two split ring resonators. Due to the strongest inductive coupling achieved for a twist angle of 180°, an attractive relative force as high as ~1200 piconewtons is realized at illumination intensities of 50 mW/µm(2). We show that a quasi-static dipole-dipole interaction model could predict well the characteristic and magnitude of the relative optical forces. We also demonstrate that although the optical force exerted on each of the split ring resonators could be oriented in a direction opposite to the propagation wave vector, the mass center of the two resonators is always pushed away from the light source.