# Free-space propagation

Free-space calculations describe a beam in a bulk medium. Choose a radial grid
when cylindrical symmetry is appropriate, a Cartesian grid for two transverse
coordinates, or a line grid for a field uniform in one direction. Read the
[spatial overview](../../introduction/spatial-description.md) first if this choice
is unfamiliar. The [radial filament lesson](../../introduction/lessons/plot_03_filament.rst)
and [Cartesian crossing beams](../../introduction/lessons/plot_04_crossing_beams.rst)
introduce the main workflows. The [focused examples](../../auto_tutorials/free_space/index.rst)
extend them to focusing, diffraction and analysis. The
[capillary coupling tutorial](../../auto_tutorials/free_space/plot_08_radial_capillary_coupling.rst)
prepares a beam in a gas gap and couples its entrance field into a capillary.

```{toctree}
:maxdepth: 1

beams
model
flux
hankel
cartesian
```