Fig. 1. Cross-sectional structure of sensor

Fig. 2. Relationship curves of reflectivity and sensitivity. (a) Reflectivity curve at different grating heights when refractive index is 1.33; (b) sensitivity as a function of grating height as refractive index changes from 1.33 to 1.34

Fig. 3. Curves of Sθ with ks in different refractive index intervals. (a) Refractive index changes from 1.33 to 1.34; (b) refractive index changes from 1.34 to 1.35

Fig. 4. Reflection spectrum curves of liquids with different refractive indexes when ks= 0.73

Fig. 5. Electric field distribution of sensor structure at incident angle of θres1 with different ks values. (a) ks=1; (b) ks=0.92; (c) ks=0.85; (d) ks=0.73; (e) ks=0.66; (f) ks=0.5