用基于德拜近似条件的矢量衍射理论研究了带有相位拓朴数的环形相位板调控高斯光束的光梯度力分布,改变相位板环形区的相对半径或当相位板的相位以一定拓扑数呈现拓扑变化时,可以调节光学系统焦点区域的光梯度力分布,形成各种非常有规则的几何形状的光陷阱,如当拓朴数分别取3,4,5,6时,可形成三角形、四边形、五边形和六边形光陷阱。此种相位板可用来构建可调的光镊系统,且通过调节相位板的各区域半径和拓扑数可以得到所希望的光陷阱。

The gradient force pattern adjusted by an annular phase distribution plate is numerically investigated by vector diffraction theory. The phase plate may alter the wavefront phase of incident Gaussian beam with tunable topological charge. Numerical simulations show that the proposed plate may adjust the tunable gradient force on the particles in the focal region. By adjusting the geometrical parameters or changing the topological charge of the phase-shifting plate,some novel polygon trap patterns may occur. For example,a triangle,quadrangle,pentagon and hexagon traps can be obained when the topological charge equals to 3,4,5 and 6,respectivily. Therefore,the phase plate may be very advantageous for constructing tunable optical traps. The method is versatile in that it allows precise control of the parameters and the possibility of generating specific patterns of optical vortices.