Fig. 4

The left column (a–d) shows the experimental and simulation results of the probe with Rr = 1.50 μm, while the right column (e–h) illustrates that of Rr = 1.90 μm, (a) and (e) Measured and (b) and (f) calculated optical field distribution and (c) and (g) calculated phase distribution and (d) and (h) calculated cross section of the probe tip. The borders of the probe structure are depicted with white dashed lines