Non-regularly shaped plasmon resonant nanoparticle as localized light source for near-field microscopy

We study numerically two-dimensional nanoparticles with a non-regular shape and demonstrate that these particles can support many more plasmon resonan ces than a particle with a regular shape (e.g. an ellipse). The electric fi eld distributions associated with these different resonances are investigat ed in detail in the context of near-field microscopy. Depending on the part icle shape, extremely strong and localized near-fields, with intensity larg er than 10(5) that of the illumination wave, can be generated. We also disc uss the spectral dependence of these near-fields and show that different sp atial distributions are observed, depending which plasmon resonance is exci ted in the particle.