A nano-confined source based on surface plasmon Bragg reflectors and nanocavity.

A type of nano-confined light source based on SPP Bragg reflectors and a nanocavity has been realized. The structures consisting of a nanocavity surrounded by annular grooves are used to obtain a single, localized and non-radiating central peak, which can be used as a nano source. Characterization of the SPP field in the vicinity of the samples with different structural parameters is accomplished by the scanning near-field optical microscope (SNOM), demonstrating the ability of the structures to enhance the peak intensity and to suppress the sidelobes. During 600 nm distance away from the sample surface, the FWHM of the central peak is below 285 nm (0.45 lambda), and the modifications of the structural parameters result in at least 1.27 times enhancement of the central peak intensity together with the sidelobe suppression of no more than 73% of the central peak intensity. Numerical simulations based on FDTD method show a good agreement with the experimental results, and give some clues to understand the physical mechanisms behind these phenomena. This type of SPP-based nano source is promising to be applied in near-field imaging, data storage, optical manipulation and localized spectrum detection.