Figure 2

(a) Measured transmission as a function of wavelength for bull's eye structures with pitches of 600 nm, 700 nm and 800 nm and for the small reference. (b) Simulated transmission for the same structures as in a. (c) Simulated absorption enhancement in a nanovolume of PbS quantum dots in the center of each bull's eye structure compared with the same structure without concentric arcs. (d and e) Electric field intensity along the x–z plane through the center of the bull's eye structure in a logarithmic scale for the bull's eye structure with a pitch of 700 nm, at wavelengths both on resonance (755 nm) (d) and off resonance (605 nm) (e). The insets present higher-magnification images of the center of the bull's eye structure. The white dashed lines indicate the bottom and top of the Au layer and the grooves. (f) Ratio of the photocurrent measured in the bull's eye structure to that measured in the large reference structure, normalized to the maximum value.