最後給出我們自行提出的5-layer結構，此設計於1.66 um ~0.62 um處皆為正光力矩，而0.62 um ~0.51 um皆為負光力矩，在特定波長達到正負力矩一分為二的效果，除此之外，y分量與z分量之光力矩於1.66 um~0.51 um波長內皆趨於零，成功降低其正負光力矩對波長之振盪行為，其設計優勢將光操作物體旋轉領域，帶來全新穩定操作微米物質旋轉的成果。 ;In this thesis, we discuss the optical force and optical torque of circularly polarized incident light on three-dimensional objects. We use circularly polarized light as incident light in different wavelengths. The electromagnetic field distribution on the grid surface is obtained by the finite element method, and the light stress on each grid point is obtained from Maxwell′s stress equation, and the overall optical force is evaluated by summing over the contributions from all grid points. Similarly, to calculate the optical torque of a three-dimensional object, we first calculate at each grid point the cross product of the position vector and the optical force, then sum over the surface contributions from the whole geometric structure. We analyzed the surface distribution of the electric field and the local oscillation behavior of the optical torque density on the surfaces of various three-dimensional structures. These results provide us with the information on how to change the wavelength of incident light to control the direction of rotation. Based on the knowledge obtained in the study of disc structures, we further designed various structures and analyzed their optical torque oscillation characteristics.
Finally, we proposed a 5-layer structure. This design has positive optical torque in 1.66 um ~ 0.62 um, and negative optical torque in 0.62 um ~ 0.51 um. In addition, the optical torque of the y and z components approach zero within the wavelength of 1.66 um ~ 0.51 um. This structure successfully reduces the unwanted oscillation behavior of the optical torque appearing in the positive or negative region, and thus has the advantage of providing the necessary stability in controlling the rotation direction of microscopic structures.