Optical transmission characteristics in the MDM waveguide coupled with N-rectangular resonators

A metal-dielectric-metal (MDM) waveguide coupled with N-rectangular cavities is proposed and its spectral features are derived and described based on the coupled-mode and multi-oscillator theory for the first time. The results of theoretical calculation and numerical simulation indicate that resonant modes are proportionally increased with the number of cavities, surprisingly, the wavelength at 716 nm is an F-P resonant mode for n = 1 and those new modes occur on both sides of 716 nm, thus a plasmonic tunable multi-modes filter and slow light effect are achieved. According to the field distributions, the resonant modes can be divided into several types: dipole, quadrupole, hexapole, eighth-pole modes and so on. Moreover, we find that the resonant transmissions are sensitively dependent on the widths and lengths of cavities as well as the vertical and horizontal distances between two cavities. In addition, the phenomena including magnitude modification, redshift, blueshift, and the disappearance and fusion of modes are clearly observed. Compared with those conventional MDM waveguides side-coupled with single or double cavities, our proposed device can provide more channels to manipulate the resonance wavelengths flexibly. Therefore, it may be applied in optoelectronic devices.