Fano resonance in MIM waveguide structure with oblique rectangular cavity and its application in sensor

• A novel and compact asymmetric MIM waveguide structure with oblique rectangular cavity is proposed.
• Fano resonances appear in the transmission spectra when the oblique rectangular cavity has different rotation angular θ.
• The mechanisms of the Fano resonances were introduced in detail.
• The asymmetric waveguide structure can serve as nanosensor to detect the refractive index changes of the filled media inside of rectangular cavity and waveguide.

In this paper, an asymmetric plasmonic waveguide structure is designed with a MIM waveguide and an oblique rectangular cavity, and its double Fano resonance characteristics and transmission properties are numerically investigated by the finite element method. The results show that double Fano resonances appear in the transmission spectra when the oblique rectangular cavity has different rotation angular θ. The double Fano resonances derive from different mechanisms, one of Fano resonances is induced by the interaction of horizontal and vertical resonance modes in the rectangular cavity, and the other is derived from rotating the rectangular cavity. So the Fano resonances can be easily tuned by the changing angle of rotation θ and structure parameters of rectangular cavity. Moreover, when the rectangular cavity is rotated to a certain angle, three Fano resonant peaks are appeared in the transmission spectra. The asymmetric plasmonic structure is also to detect the refractive index changes of the filled media inside of rectangular cavity and waveguide, which reveals a potential sensors application of the MIM waveguide with oblique rectangular cavity.