Coupling effects in single-mode and multimode resonator-coupled system.

We have proposed a simple metal-dielectric-metal (MDM) waveguide system side-coupled with single-mode and multimode resonators. This proposed structure can achieve a typical dual plasmon-induced transparency (PIT) effect in the transmission spectra. The two PIT peaks exhibit opposite evolution tendencies with the increase in the depth of stubs. A multimode-coupled mode theory (M-CMT), confirmed by simulated results, is originally introduced to investigate the coupling effects of the proposed structure. Compared to the previous reported multichannel filters, the proposed structure includes obvious advantages, such as structural simplicity and ease of fabrication. In addition, the sensing characteristics of the proposed structure based on PIT effects are discussed numerically. The results demonstrate that the proposed structure is suitable for applications in multichannel filters, optical switches, and sensors.