Gain-induced large optical torque in optical twist settings

Li Genyan^{1, 2, 3}, Li Xiao⁴, Zhang Lei^{2, 3, 5}, Chen Jun^{1, 2, 3, †}

Structures are the same as Figs. 3(a) and 3(b) except the separation between adjacent spheres D = 2a+0.0008 μm. The refractive index of Ag is modeled by Drude model,^[6,40,41] and n_gain = 2 – 0.005i. (a) Optical torques exerted on the upper Ag layer and the lower gain layer in a gain–Ag double-layer cluster. (b) Optical torques exerted on a single Ag layer cluster and that on the upper Ag layer in a Ag–Ag double-layer cluster are plotted compared to the partial view of the black line in panel (a).