Plasmonics

The photonics beyond the diffraction limit

The spot size of light is limited to the wavelength scale because of the diffraction of light. Surface plasmon polariton (SPP) has attracted significant interest as a nanoscale light for overcoming this diffraction limit. SPPs are electromagnetic waves coupled to the free electrons in the metal, and offer the interesting physics, i.e., super focusing, slow light, beyond the diffraction limit. Our group studies the physics of SPP, and designs plasmonic devices in the visible, infrared and THz region, to realize the innovative photonics. Our research is currently organized in the following

Superfocusing, Negative Refraction, Slow Light

A design for the SPP guiding (Plasmonic waveguides) allows us to induce interesting phenomena, such as superfocusing, negative refraction and slow light. We have reported the theoretical analysis of these phenomena. The figure on the right shows the simulated result of negative refraction in the plasmonic waveguide. We create new applications based on interesting physics of SPPs.

Nano optical integrated circuits

SPP waves can be guided by metallic nanostructures beyond the diffraction limit. This remarkable characteristic has unique prospects for the design of nano optical integrated circuits. The concept of plasmonics offers the opportunity to create innovative optical circuits that have the speed of dielectric photonics and the size of nanoelectronics. The figure on the right shows the observation of long-range SPPs (LR-SPPs) propagating the silver nanowire with a width of 200 nm. We design the basic components of nano optical integrated circuits, such as optical waveguides, transistor and antenna, based on plasmonics.

Control of thermal radiation

The broad spectrum of thermal radiation depends on the temperature. Also, thermal radiation can be controlled by means of various modes on the surface structure of the source. This is spectral controls of thermal radiation. We have studied spectral controls in the mid-infrared or terahertz frequency region by spoof surface plasmon (spoof SP) on a metal structure and plasmonic resonance in metamarterial. The right figure shows a sample of metamaterial with Split-Ring Resonator (SRR) and measured thermal radiation spectra enhanced by SRR. These structure will lead to thin-film emitters (from terahertz to visible frequency) in the future.