If you’ve ever cracked open Shaul Mukamel’s Principles of Nonlinear Optical Spectroscopy and felt your brain melting, you aren’t alone. It is the "Bible" of the field, but it’s written in a language that assumes you’re already a math prodigy.
The third-order polarization (your signal) is: [ P^(3)(t) \propto \int_0^\infty dt_3 \int_0^\infty dt_2 \int_0^\infty dt_1 ; R^(3)(t_1, t_2, t_3) ; E_3(t - t_3) E_2(t - t_3 - t_2) E_1(t - t_3 - t_2 - t_1) ] If you’ve ever cracked open Shaul Mukamel’s Principles
In a real experiment (like 2D Electronic Spectroscopy or Transient Absorption), you control the delays between pulses ( If you’ve ever cracked open Shaul Mukamel’s Principles