Plasmon Localization and Giant Fields in an Open-Resonator Metasurface forSurface-Enhanced-Raman-Scattering Sensors
Andrey K. Sarychev, А. В. Иванов, Andrey N. Lagarkov, Ilya A. Ryzhikov, Konstantin Afanasev, I. V. Bykov, Grégory Barbillon, Nikita Bakholdin, M. S. Mikhailov, Alexander Smyk, Alexander Shurygin, А.Н. Шалыгин
Abstract
We present metal-dielectric metasurfaces fabricated from metal periodical nanograting deposited on a dielectric substrate. The metasurface consists of a modulated dielectric, which is covered by a thin silver layer. The metasurface operates as an open plasmon resonator. The theory of plasmons excited in the open resonator formed by a metal nanograting is presented. The large local electromagnetic field is predicted for optical frequencies. The excitation of plasmons is experimentally demonstrated in the metasurface designed on a 4-in. $\mathrm{Si}$ wafer. The enhancement of the local electric field results in surface-enhanced Raman scattering (SERS). To investigate the SERS effect, the metasurface is covered with a thin layer of the 4-mercaptophenylboronic acid that molecules form covalent bonds with the silver nanolayer. The enhancement of the Raman scattering serves as a proof of concept. We obtain a detection limit of 230 nM for molecules of 4-mercaptophenylboronic acid.