Cavityless plasmonic metal-insulator-metal nanoresonator

Optical resonators are essential components for photonic devices and systems. However, at the nanoscale, it becomes difficult to create devices with the predetermined properties due to imperfections in the fabrication process, since the resonances are determined by the shape and size of the cavity. Here, we propose and demonstrate a fundamentally different type of resonators: a cavityless plasmonic resonator, – which paves the way to a whole new approach for light manipulation at the nanoscale. The operating principle of such a resonator is not based on reflection from the cavity boundaries and, therefore, the resonant modes almost do not depend on the geometrical parameters. At the same time, the quality factor is as high as for the best plasmonic resonators operating in the same spectral range. This feature makes the proposed cavityless resonators very attractive for diverse applications in ultrafast and deep-subwavelength photonics.