The main idea of this paper is to design an array of core-shell plasmonic nanoparticles manipulating a desired near-field focusing pattern in optical spectrum. The interactions between the array elements are formulated by using dyadic Green’s function analysis and by employing the closed-form formula for electric polarizability of each plasmonic particle (dipolar mode approach). The point-matching technique is applied to optimize the plasmonic-array field performance as close as to the desired near-field pattern. The final equation for finding the polarizability of each element will be a system of nonlinear equations that can be solved successfully by Levenberg-Marquardt technique. Controlling the inner and outer radii of each element using magnitude and phase contours of polarizability demonstrates a near-field subwavelength concentration. The accuracy of our theoretical model is successfully compared with a full-wave numerical analysis using CST commercial software. Interesting physical features for the optical near-field engineering are illustrated.

• Received 23 December 2009

DOI:https://doi.org/10.1103/PhysRevB.82.035117