Fig. 2. Simulation and experimental result of the photonic nanojets.

(a) Finite element method (FEM) simulation result of a 20 μm polystyrene microsphere (n=1.58) in water (n=1.33) with a hard PDMS (n=1.41) film on the bottom as outer medium conditions. The vertical graph shows the focal distance from the bottom of the microsphere to the PDMS membrane. The horizontal graph represents the focused photonic nanojets and its full-width half-maximum. (b) FEM simulation result of the focal distance map as a function of the microsphere diameter and refractive index. The red color (25 μm focal distance) to purple color (3 μm focal distance) showed each focal distance depending on the size of the microsphere and refractive index. (c) Microscopic images of the microsphere magnification capability. The left panel is shown without microsphere condition. The right panel shows microsphere magnification at the same regions of interest as seen in the left panel. The target sample was 500 nm green fluorescence nanoparticles and thickness of the hard PDMS membrane was 7 μm. The scale bar is 10 μm.