Population inversion in two-level systems possessing permanent dipoles

TL;DR

This paper demonstrates steady-state population inversion in a two-level system with permanent dipoles, driven by resonant and near-resonant fields, enabling new control over quantum states and optical properties.

Contribution

It introduces a method to achieve population inversion in two-level systems with permanent dipoles using dual-field driving, a novel approach not previously reported.

Findings

Population inversion achieved in systems with permanent dipoles.

Large refractive indices can be realized.

Diagonal matrix elements can be extracted from spectra.

Abstract

Bare-state population inversion is demonstrated in a two-level system with all dipole matrix elements nonzero. A laser field is resonantly driving the sample whereas a second weaker and lower frequency coherent field additionally pumps it near resonance with the dynamically-Stark-splitted states. Due to existence of differing permanent dipole moments in the excited and ground bare states, quantum coherences among the involved dressed-states are induced leading to inversion in the steady-state. Furthermore, large refractive indices are feasible as well as the determination of the diagonal matrix elements via the absorption or emission spectra. The results apply to available biomolecular, spin or asymmetric quantum dot systems.