Fig. 1. Schematics of three-dimensional simulation models and their parameter setting. (a) Three-dimensional schematic of UMS; (b) three-dimensional schematic of BHMS; (c) three-dimensional schematic of flat structure; (d) parameter setting of UMS ; (e) parameter setting of BHMS

Fig. 2. Refractive index n and extinction coefficient k curves of single crystal silicon. (a) Refractive index n curve; (b) extinction coefficient k curve

Fig. 3. Reflectance curves of UMS. (a) D= 250 nm; (b) H= 600 nm

Fig. 4. Equivalent refractive index curves and average reflectance contour plot of UMS. (a) Equivalent refractive index curves of UMS when D=250 nm; (b) reflectance contour plot of UMS

Fig. 5. Average reflectance contour maps of BHMS. (a) D1=D2=250 nm; (b) H1=H2=600 nm

Fig. 6. Reflectance curves of BHMS and UMS

Fig. 7. Electric field intensity distributions of four structures on Y=0 section. (a) Slab silicon structure; (b) UMS(D=200 nm); (c) UMS(D=300 nm); (d) BHMS(D1=300 nm & D2=200 nm)

Fig. 8. Reflectance curves of THMS and BHMS