Nanoscale Optical Display and Sensing Based on the Modification of Fano Lineshape

摘要

The shift of Fano resonances has been widely exploited to realize biomedical sensing, optical filtering, and optical switching. Here, the formation of Fano resonances in the scattering spectra of silicon nanoparticles excited by surface plasmon polaritons is reported and the modification of Fano lineshapes is demonstrated. It is revealed that the subradiant and superradiant modes responsible for the formation of Fano resonance originate from the coherent interaction of the electric and magnetic dipoles excited in the silicon nanoparticle with their mirror images induced by a thin metal film. The modification of the asymmetry parameter q can be realized by simply adjusting the angle of the incident light or by slightly varying the environment refractive index. The tuning of the q value is accompanied by the variation of the field enhancement factors and manifested in the color change of the scattered light. The strongest enhancement of both electric and magnetic fields can be achieved at the point of contact between the silicon nanoparticle and the metal film for the symmetric Fano lineshape (q approximate to 0). These findings indicate the potential applications of such a hybrid metal-dielectric system in sensing, color display, and strong light-matter interaction.