Group delay dispersion

The group delay dispersion (GDD) of an optical element is the derivative of the group delay with respect to angular frequency, and also the second derivative of the optical phase. $D_2(\omega) = -\frac{\partial T_g}{d \omega} = \frac{d^2 \phi}{d\omega^2}$. It is a measure of the chromatic dispersion of the element. A parameter independent of the length of the material is the group velocity dispersion (GVD).

Equivalent Parameters

GDD is related to the total dispersion parameter $D$ as

$D_2(\omega) = -\frac{2\pi c}{\lambda^2}D_{tot}$

References

Encyclopedia of Laser Physics and Technology article on Group Delay Dispersion