SHEDDING SOME LIGHT INTO THE ELECTROMAGNETIC FIELD INSIDE HOT SPOTS

EDUARDO M. PERASSI; LUIS R. CANALI; EDUARDO A. CORONADO

Buenos Aires

Congreso; 10th International Conference of Near-Field Optics, Nanophotonics and Related Techniques; 2008

Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires.

Understanding the factors which control the way light interacts with matter in the nano-scale is a fundamental issue in optoelectronics and nanophotonics, and many applications such as surface enhanced spectroscopies for bio-chemical sensing, optical signal processiing relies on the surface bound optical excitations in metallic nanoparticles. An accurate evaluation of the electromagnetic field enhancement is of upmost importance to evaluate the relative contributions of chemical and electromagnetic mechanism proposed for SERS based on purely electromagnetic fields arguments. Although for some simple shapes such as spheres and spheroids analytical solutions to Maxweell equations make it possible to evaluate accurately the electromagnetic field enhancement, for arbitrary shaped NPs one has to deal with numerical methods, which relies on discretization of the NP on finite grids. In this sense, two main problems arises: the convergence with respect to the grid size and the accuracy of the electromagnetic field near the NP surface. In this work , using the Discrete Dipole Approximation, we give an heuristic approach that allow us to shed some light into both problems, by a novel approach based on an empirical law. This approach is applied for an accurate evaluation of the electromagnetic field generated around some representative NP shapes such as silver spheroids, cylinders or prisms.