Pulse amplification in a closed loop $\Lambda$ system with permanent dipole moments

TL;DR

This paper investigates how permanent dipole moments in a closed loop $b1$ system enable probe pulse amplification and multi-photon excitation, revealing new possibilities for light manipulation in quantum systems.

Contribution

It demonstrates that PDMs enable probe amplification and multi-photon processes in a closed loop $b1$ system, which were previously forbidden.

Findings

Probe pulse is amplified with Gaussian shape preserved.

PDMs enable two-photon excitation at twice the control frequency.

Amplification occurs during propagation due to modified Rabi frequencies.

Abstract

Propagation of a weak Gaussian probe pulse through a closed loop $\Lambda$ system with permanent dipole moments (PDMs) is investigated in presence of a strong control field along with a third field. The presence of PDMs allows multi photon excitation, which are otherwise forbidden. The PDMs modify the Rabi frequencies of the probe, control, and the third field inside the medium which noticeably affects the propagation of probe pulse. The probe pulse is amplified during propagation with its Gaussian shape intact. Due to unprohibited two photon excitation it is possible to amplify a probe pulse whose frequency is twice of the control field's frequency, with the help of the third field.