Coherent Transients From Three-level Λ System With Local Field: Analytical Results

In this paper, we analyze the nonlinear response of a three-level A model system, using a perturbation theory based on the Liouville equation . of motion and considering the Lorentz local field effect. In the nonlinear optical response, two consecutive coherent pulses with the wave vector k1 and k2 generate new light waves in the new directions. The terahertz emission, which is a second-order response, and the four-wave mixing signal, a third response, are given the expressions related to the Lorentz local field factor l. We found a four-wave mixing signal in the direction 2k2-k1 for the negative time delay, and the frequency of the four-wave mixing signal has a shift related to the Lorentz local field factor l.