Fig. 5: Excitations of SPs with the photonic chip for surface imaging.

a Schematic of the modified photonic chip where the top multilayer was replaced with a thin silver film to demonstrate the excitation of SPs under normal incidence and the ability for surface imaging. The specimens to be imaged are the single polymer nanowire placed on a microwire, and polymer nanoparticles of different diameters. The modified photonic chip was also used in the standard brightfield microscopy shown in Fig. 4a with a regular air objective (×60, NA = 0.7). b The image of the polymer wires under the illuminations of the excited surface plasmons (SPs). c Corresponding brightfield image of the polymer wires. d Intensity profiles extracted along the white dashed lines on b, c. The dashed red lines indicate the levels used to determine the image contrast (CR). e, f The surface images and brightfield images of the polymer nanoparticles with diameter at 200 and 50 nm, respectively. Scale bars, 10 μm.