Population Inversion

Cai Xun-Ming, 邹光龙 ZOU Guang-long

In order to find out the effect of atomic motion on the population inversion of two atoms,the atomic states were analyzed by the method of quantum mechanics.It was found that the population inversion of two atoms was related to the field mode structure in an optical resonant cavity when the atoms were moving and the optical field was in coherent state.When two atoms in the cavity were fixed at initial time,the evolvement of population inversion of two atoms was periodic in the case of a small average photo number,and there were collapses and revivals of atomic inversion in the case of a large average photo number.The evolvement of population inversion of two atoms became well-regulated orderly under the coherent cavity field when atoms were in motion at initial time.The population inversion of two atoms will evolve in different periods when the two atoms move in axial direction at different velocity.The period of population inversion is the lease common multiple of periods of coupling coefficients between two atoms and field.When there are more average photon number in the cavity,the oscillation of population inversion will be faster.So it is possible to control the population inversion by properly choosing the velocity of atoms and the initial field.

Prem Ballabh Bisht

V. B. Krasovit︠s︡kiĭ, A.R. Linetskii

Yifu Zhu

We analyze transient properties of light amplification without population inversion (LWI) in a closed three-level @sV -type system and study the system evolution from transient LWI into steady-state LWI. From the time evolution of the atomic coherence and population distribution with and without an incoherent pump field, we elucidate the light amplification mechanism and derive the conditions under which the @sV system exhibits LWI in any state basis. We derive analytical solution for the steady-state LWI and discuss other mechanisms of light amplification such as stimulated Raman scattering and population inversion in the dressed states. \textcopyright{} 1996 The American Physical Society.

Bo Y. Chang, Sheokmin Shin, Ignacio R. Solá

Quantum systems with sublevel structures prevent full population inversion from one manifold of sublevels to the other using strong ultrafast resonant pulses. In this work we explain the mechanism by which this population transfer is blocked. We then develop a novel concept of geometric control, assuming full or partial coherent manipulation within the manifolds and show that by preparing specific coherent superpositions in the initial manifold, full population inversion or full population blockade, {\it i.e} laser-induced transparency, can be achieved. In particular, by parallel population transfer we show how population inversion between the manifolds can be obtained with minimal pulse area. As the number of sublevels increases, population inversion can overcome the pulse area theorem at the expense of full control over the initial manifold of sublevels.

Daniel P. Sheehan