What we are doing
We study optical properties of metallic nanostructures and their application to optical devices. The metallic nanostructures show interesting optical properties different from other materials such as a bulk metal, a semiconductor and polymers. For instance, gold nanoparticles are orange or red because free electrons in the nanoparticles coorperatively oscillate on irradiation of green light, just like that a tuning fork is resonant with a sound at a certain frequency. This effect is called localized surface plasmon resonance (LPR). The LPR occurs not only in metallic nanoparticles but also at a rough metallic surface. Since the resonance condition is sensitive to the dielectric constants of the surrounding medium, it can be applied to chemical and bio sensors. The LPR also produces a greatly enhanced electric field adjacent to the nanostructure. This can be applied to huge nonlinear optical effects and the surface-enhanced Raman scattering (SERS). The kajikawa research group aims at development of optical devices utilizing the localized surface plasmons. The optical devices developed here involve optical fiber biosensors, biochips and non-contact electric field probes. We are also investigating new mechanisms to excite surface plasmons, such as plasmonic crystals and plasmonic optical antennas. These surface plasmon structures will open new paradigm of optical materials in future. Since these works are quite multidisciplinary, the background of our members is broad and collaborations with research groups over the world and over the fields are essential.
Dr. Kotaro Kajikawa, Professor
School of Engineering,
Department of Electrical and Electronic Engineering,
Tokyo Institute of Technology