So i seem to have run into a problem. I found a way to accurately measure white light pulses but i still need some help doing the math. The information i have is: 1) wavelength vs time graphs [of the white light] 2) Material - using 2 fused silica prisms to compress the white light The math i've been following is from Diels - ultrashort laser pulse phenomena pg 100-117 (latest edition) - pdf attached Q: How do i calculate GVD of the pulse in the graph above? Please let me know if you have any idea - i am fairly new to theoretical aspects in the field! Thanks! UPDATE: The derivation of GVD from Vg[group velocity] is pretty clear. But in order to obtain the GVD of the graph above, i need the Vg from the information provided[the graph]. Thats where im having trouble: The graphs gives us: [w=omega=angular freq] dt/dw [[tex]\lambda[/tex]=2*[tex]\pi[/tex]*c/w] dw/dk (i.e. Vg) =dt/dw * dk/dt - where k==[w*n(w)]/c and w=w(t) this seems like a loop!