Narrowing of the homogeneous two-photon absorption line width in two-level dipolar system

摘要

We study narrowing of nonlinear two photon absorption line shape in system with non-zero permanent dipole moment difference between the ground- and excited state. The temperature-induced broadening of one photon absorption (1PA) and two photon absorption (2PA) line shapes is modeled by subjecting the resonance transition frequency to random fluctuations of varying amplitude and by solving numerically the corresponding two-level density matrix equation of motion. We show that under conditions, when 1PA and 2PA transitions are both far from saturation, the 2PA homogeneous line width may be as much as 25% narrower than the corresponding 1PA line width. This offers novel possibilities for reducing the temperature-induced dephasing in quantum computing, quantum memory and other applications based on coherent multi-photon interactions.