Ultrashort Laser Pulse Phenomena, 2nd Edition

Multiphoton Coherent Interaction 245

(a) (b)

Figure 4.7 The problem of reaching a high level with a harmonic ladder (a), and the multiple-pulse

multiphoton coherent solution (b).

section, Section 4.4.3. we will proceed from this more general situation to the

particular approximation that leads to the multiphoton analog of Bloch’s optical

equations.

4.3.2. Multiphoton Multilevel Transitions

General Formalism

The complex atomic–molecular system is represented by the unperturbed

Hamiltonian H

0

to which corresponds a set of eigenstates ψ

k

of energy ω

k

.

In the presence of an electric field E, the state of the atomic–molecular system is

described by the wavefunction ...