Docs: Hint FWHM_I in Gaussian Beam (#1215)

Hint that the pulse length in theory is not the pulse length measured in experiments (and how to translate).

1 files changed, 3 insertions, 1 deletions

diff --git a/Docs/source/running_cpp/parameters.rst b/Docs/source/running_cpp/parameters.rst
index c3759260e..a68a058f5 100644
--- a/Docs/source/running_cpp/parameters.rst
+++ b/Docs/source/running_cpp/parameters.rst
@@ -717,7 +717,7 @@ Laser initialization
 
 *  ``<laser_name>.profile_duration`` (`float` ; in seconds)
 
-    The duration of the laser, defined as :math:`\tau` below:
+    The duration of the laser pulse, defined as :math:`\tau` below:
 
     - For the ``"gaussian"`` profile:
 
@@ -725,6 +725,8 @@ Laser initialization
 
         E(\boldsymbol{x},t) \propto \exp\left( -\frac{(t-t_{peak})^2}{\tau^2} \right)
 
+    Note that :math:`\tau` relates to the full width at half maximum (FWHM) of *intensity*, which is closer to pulse length measurements in experiments, as :math:`\tau = \mathrm{FWHM}_I / \sqrt{2\ln(2)}` :math:`\approx \mathrm{FWHM}_I / 1.174`.
+
     - For the ``"harris"`` profile:
 
     .. math::