NumericalAperture¶

Type:	float
Range:	[0, inf]
Default:	-/-
Appearance:	optional

Use the numerical aperture $\mathrm{NA}$ to define the range of the computed Fourier spectrum. When not set the entire propagating spectrum is computed.

With the notation of the parent section, Fourier modes with

$\begin{eqnarray*} \Re \left(\frac{\pvec{k}_\perp}{k_0} \right) \leq \mathrm{NA} \end{eqnarray*}$

are computed.

Note

For fully periodic problems this parameter can be used to compute evanescent Fourier modes as well. Non propagating parts of the continuous spectrum are disregarded irrespective of the set $\mathrm{NA}$ value.