Optical path length $L$, $$L=\sum _{i=1}^N{h}_i{n}_i.$$

Time of flight of Gaussian beam through optical path length $L$, $$t=\sum _{i=1}^N\frac{h_i}{v_{\mathsf{g},i}}.$$

Carrier-envelope phase ${\phi }_{\mathsf{CE}}$ is the phase difference between the maxima of (i) oscillating field intensity and (ii) carrier envelope. After propagating distance $L$ in medium, the CE phase changes due to diffence of phase and group velocities, $$\mathrm{\Delta }{\phi }_{\mathsf{CE}}={\omega }_0(\frac{1}{v_{\mathsf{g}}}-\frac{1}{v_{\mathsf{p}}})L.$$ CE phase shift is proportional to the first derivative of refractive index over the wavelength, $$\mathrm{\Delta }{\phi }_{\mathsf{CE}}=-2\pi L\frac{\partial n(\lambda )}{\partial \lambda }.$$

Optical path length $L$, $$L=\sum _{i=1}^N{h}_i{n}_i.$$

Time of flight of Gaussian beam through optical path length $L$, $$t=\sum _{i=1}^N\frac{h_i}{v_{\mathsf{g},i}}.$$

Carrier-envelope phase ${\phi }_{\mathsf{CE}}$ is the phase difference between the maxima of (i) oscillating field intensity and (ii) carrier envelope. After propagating distance $L$ in medium, the CE phase changes due to diffence of phase and group velocities, $$\mathrm{\Delta }{\phi }_{\mathsf{CE}}={\omega }_0(\frac{1}{v_{\mathsf{g}}}-\frac{1}{v_{\mathsf{p}}})L.$$ CE phase shift is proportional to the first derivative of refractive index over the wavelength, $$\mathrm{\Delta }{\phi }_{\mathsf{CE}}=-2\pi L\frac{\partial n(\lambda )}{\partial \lambda }.$$