Dual-planar-waveguide sensor with TMDC materials based on Fano resonance

With the rapid development of sensor technology, Fano resonance sensors have attracted much attention due to their high sensitivity. In this paper, Fano resonance is achieved by coating a few-layer transition metal dichalcogenides in two planar waveguides, and the coupling mechanisms governing the two planar waveguides and the transition metal dichalcogenides are analyzed in detail. The results show that the intrinsic loss of transition metal dichalcogenides induces different quality factors between the two waveguides. The low-quality-factor waveguide supports wide resonance, while the other with a higher quality factor generates ultra-narrow spectral features. Fano resonance arises from the coherent coupling of these quality factors. For transition metal dichalcogenides including MoS₂, WS₂, MoSe₂ and WSe₂, the maximum sensitivity obtained through systematic optimization are 9930 RIU^-1, 7882 RIU^-1 , 9967 RIU^-1 and 8915 RIU^-1 respectively. This sensor can detect the refractive index of biomolecules through the Fano line-shape reflectance curve, which is more advantageous as biosensor in aqueous solutions.