Absorption with inversion and amplification without inversion in a coherently prepared V system: A dressed-state approach

Abstract

Light induced absorption with population inversion and amplification without population inversion (LWI) in a coherently prepared closed three level Vtype system are investigated. This study is performed from the point of view of a two color dressed state basis. Both of these processes are possible due to atomic coherence and quantum interference contrary to simple intuitive predictions. Merely on physical basis, one would expect a complementary process to the amplification without inversion. We believe that absorption in the presence of population inversion found in the dressed state picture utilized in this study, constitutes such a process.Novel approximate analytic time dependent solutions, for coherences and populations are obtained, and are compared with full numerical solutions exhibiting excellent agreement. Steady state quantities are also calculated, and the conditions under which the system exhibits absorption and gain with and without inversion, in the dressed state representation are derived. It is found that for a weak probe laser field absorption with inversion and amplification without inversion may occur, for a range of system parameters. *shuker@bgumail.bgu.ac.ilRecently there has been tremendous interest in the study of light amplification and lasing without the requirement of population inversion (LWI), potentially capable of extending the range of laser devices to spectral region in which, for various reasons, population inversion is difficult to achieve. These spectral regions include UV which can be obtained from atomic vapor, and mid-to-far infrared, obtained by interssubband transitions in quantum wells. Many models for LWI have been proposed, mostly three and four level schemes, in Λ and V configurations. The dependence of optical gain on system parameters has also been investigated [1-17].The key mechanism, which is common to most of the proposed schemes, is the utilization of external coherent fields, that induce quantum coherence and interference in multilevel systems.An exception of LWI without the use of coherent fields was also reported [9]. In particular it was shown that if atomic coherence between certain atomic states is established , different absorption processes may interfere destructively leading to the reduction or even the cancellation of absorption [7,13]. At the same time stimulated emission may remain intact, leading to the possibility of gain even if only a small fraction of the population is in the excited state.Experimental observations of inversionless gain and lasing without inversion have been reported by several groups [18][19][20][21]. Inversionless lasers have been shown to have unique properties such as non classical photon statistics and substantially narrow spectral features [22,23]. In a recent paper, Y. Zhu [12] analyzed the transient and steady state properties of light amplification without population inversion in a closed three level V type system in the bare state basis.Steady state dressed state populations were also calculated, in the limit of strong...

Control of amplification without inversion in H2 and LiH molecules: Dependence on relative magnitude of probe and coherent field Rabi frequencies in three-level Λ system

“…When ∆ < ∆ c , the population distribution satisfies ρ 33 > ρ 22 > ρ 11 . But when ∆ > ∆ c , the population distribution satisfies ρ 22 > ρ 33 > ρ 11 , and the population inversion for the Raman transition |2 → |3 occurs.…”

“…ladder, V , Λ etc. Physical picture of AWI has also been analyzed in dressed state approach [8][9][10][11]. In most of the theoretical studies, analytical expressions for coherences and populations in the steady state limit were derived by using first-order approximation, i.e.…”

Quantum resonances by sequential pulsed excitation with pulse repetition rate at fractional atomic frequencies

“…Left (red online) and right (blue online) couples of arrows show the main resonances at sum and difference frequencies ω ab + Ωac and ω ab − Ωac, respectively. Figure 3 also demonstrates quantum-interferencerelated phenomena, accompanying combination resonances, namely, Coherent Population Trapping (CPT) [7,8], Lasing/Gain Without Inversion (LWI/GWI) [9], and Absorption Despite Inversion (ADI) [10,11]. Indeed, one can observe from Fig.…”

Coherent control of AC Stark allowed transition in Λ system

“…The electric field component of the driving laser field breaks the space spherical symmetry and renders the parity not well defined, as in dc Strark effect. In other words, the presence of a strong driving field exerts ac Strark effect and thus breaks the spherical symmetry of the system and creates an infinite ladder of dressed states [11,12]. An interesting signature of the forbidden transitions is the antisymmetric character of the gain and dispersion on the Rabi sidebands.…”

“…We call such dynamically allowed transitions ac-Stark allowed (ACSA) transitions. In other words the interaction with two coherent fields, at least one of which is strong, creates an infinite ladder of dressed states [11,12], so that transitions between the dressed states are not necessarily constrained by the selection rules for a free atomic system. In a sense this is a different variant than the usual EIT or LWI schemes as here the transition is forbidden to begin with and there is no issue of population inversion.…”