The Sensing Applications in U-Shape Structure Based on Dual Transparency Windows

We have researched a U-shape structure that consists of three vertical cavities coupled with bus wave-guide. The theoretical results based on the coupled mode theory are consistent with simulation results. We demonstrate that the interaction among two bright and one dark modes lead to dual plasmon induced transparency. Meanwhile, it is found that the lateral displacement S plays an important role in the transmission property, and the transmission dip with different transmittance in various lateral displacement S has been explained theoretically. Moreover, the nano sensor has a sensitivity of 1225 nm shift per refractive index unit, and the figure of merit is up to 62.5. The proposed structure has the advantages of simple and compact structure, easy fabrication, and the ultra-compact structure holds great potential to the control of light in highly integrated optical circuits and nano sensor.