All the examples have been run with Matlab R2016b.

The main script is main.m, where the user specifies a gap width in nanometers, an incident wavelength in microns and a value for the b factor that multiplies beta^2 (b=0 is LRA, and b=1,1.5 have been used for the paper). This is the only routine that needs to be executed by the user. All the other routines are in a subfolder that is automatically added to the path.

run_example.m loads the mesh used for the simulations and calls the maxwell solver. Runtimes of each subpart are shown in screen. If b>0 the hydrodynamic model is solved, which requires more RAM than the b = 0 case (all the examples can be run in a machine with 128GB of RAM).

The solver outputs the values of the electric (EDG), magnetic (HDG),current density (JDG) and electron density (RDG) at the high-order nodes of the discretization as complex numbers. In run_example.m we then compute the transmission and the field enhancement as specified in the SI.

Back to main.m, we also provide a routine for plotting any of the above solution fields or modifications thereof (e.g. real part, absolute magnitude) on any z-constant surface. The user must specify the component of the solution field to plot as well as the z-value where to plot (if it does not coincide with a z-value that belongs to the discretization, we instead show the solution field at the z that is closest to z-value and is in the discretization). A couple of examples are provided.