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The predetermined field distributions can be achieved by phase modulation of the source field to manipulate the propagation of surface plasmon polaritons (SPPs).The modulations of the radius of the circular slit are according to the phase distributions on the slit,which are calculated by using the Gerchberg Saxton algorithm with the known field.We design the surface geometric shape of the radius-varied circular slit for exciting the SPP field with the linear,triangular,square and circular distribution characteristics,respectively.The slit structure designed for the circular field distribution is a plasmonic vortex lens that can be used to generate the vortex with the specified size of the primary ring,which shows that this heuristic method has the potential to devise plasmonic devices.