Lez #37+38 Double sided Feynman diagrams: linear absorption and pump-probe (3rd order)

  We introduced the double sided Feynman diagrams to describe the perturbative expansion of the polarization, end explicitly evaluated the linear absorption of a two level system.

We started to extend the same approach to third order processes. Among them, pump-probe experiments with the first 2 simultaneous interactions with the pump, and the third interaction with a probe. This originates stimulated emission (SE), bleaching and excited state absorption (ESA). We commented on the differences between bleaching and SE.