Optical property of rectangular nanopit array and the investigation of coupling between adjacent pits

We combine rectangular nanopits of different lengths and find that strong localized field regularly transfers from one pit to another as incident wavelength increases. This phenomenon is due to the ability of rectangular pits to tune resonant wavelength by varying the structural parameters. The relation between pit structure parameters and resonant wavelength is explained by the waveguide theory. Furthermore, the coupling between two adjacent pits and its influence on electric field distribution and resonant wavelength are investigated. The red-shifts of resonant wavelength caused by coupling are explained by Bethe’s cavity coupling theory.