Fig. 5: Calibration measurement and experimental localization results.

a The directivity parameters D₀ (red dots), D₆₀ (green dots), and D₁₂₀ (blue dots) are plotted against the corresponding positions set by the piezo stage. The semi-transparent color-matching planes correspond to two-dimensional linear equations that are fitted to the experimental data. The gradient vectors of the individual planes are plotted as arrows in the hexagonal inset, while the actual orientations of the waveguides are indicated as black dotted lines. b The directivity D₀ is plotted for a line scan along the x-axis with a step size of 25 nm. For each position (denoted by one single color) set by the piezo stage, 61 camera frames are captured and the directivity parameters are determined. c For the same scan, the two-dimensional position is calculated using the calibration data.