To get high resolution image, there are two options:
1: using interpolation: https://optics.ansys.com/hc/en-us/articles/360034925893-interp-Script-command this is a linear method. You can also use matlab, but before sending data to matlab, please interpolate the data as matlab uses linear data, but Lumerical uses auto- non-uniform mesh. This method does not increase accuracy.
2: using finer mesh and rerunning the simulation. At the same time you may need to increase the number of PML layers to keep the total thickness the same. This increases the accuracy.