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The semiclassical theory
Published in M. G. Benedict, A. M. Ermolaev, V. A. Malyshev, I. V. Sokolov, E. D. Trifonov, Super-radiance, 2018
M. G. Benedict, A. M. Ermolaev, V. A. Malyshev, I. V. Sokolov, E. D. Trifonov
In this final section we describe briefly lasing without inversion, a phenomenon that has been widely discussed in the course of the last few years. Lasing without inversion may take place in three-level resonant atomic systems and, like super-radiance, results from atomic coherence. This effect was pointed out first by Kocharovskaya and Khanin [KK88] and by Harris [H89]. These authors paid attention to the fact that even without a positive population difference of the levels in question one may obtain a positive gain provided that an additional intermediate level coupled coherently to the upper level, is taken into account. The corresponding ‘Λ’ level scheme is depicted in figure 5.12. The field ε0affects the transition 1 ↔ 3 whilst the field εc produces a ‘trapped’ (see below) state of the transition 1 ↔ 2. The latter is crucial for the effect in question. We shall consider the case where both fields are resonant with the corresponding transitions. The level scheme is actually the same as for Raman scattering, but here εc is an external field which couples levels 3 and 2. The damping constant Γ describes the decay of the upper level to others, and it is assumed to be much larger than spontaneous emission rates of all other actual transitions which will be neglected further on.
Sub-recoil-limit laser cooling via interacting dark-state resonances
Published in Journal of Modern Optics, 2019
Vase Moeini, Seyedeh Hamideh Kazemi, Mohammad Mahmoudi
On the other hand, the phenomenon of dark-state or coherent population transfer (28), a well-known concept in quantum optics and laser spectroscopy, forms the base for a wealth of important effects, such as electromagnetically induced transparency (EIT) (29,30), lasing without inversion (31), femto-second generation (32), and slow light (33–35). In this context, sub-recoil laser cooling methods have been proposed which take advantage of the dark-state resonances (36–39). Typically, the recoil limit corresponds to a temperature of between and K. A particular instance of these methods is a scheme based on velocity-selective optical pumping of atoms into a nonabsorbing coherent superposition of states, leading to transverse cooling of He atoms to a temperature lower than both usual Doppler cooling limit and the one-photon recoil energy (36). It is imperative to point out a remarkable work that suggested the use of spectral feature generated by an EIT in a Lambda-type three-level system for approaching a temperature around the single-photon recoil energy (39). In spite of the pronounced success, there still exists a continuing need for lower temperatures than conventional laser cooling techniques can provide.
Optical gain in an optically driven three-level
Published in Journal of Modern Optics, 2018
C. W. Ballmann, V. V. Yakovlev
Two- and three-level systems have been studied extensively in recent years. Such simple systems are perfect for theoretically and experimentally testing quantum theory and light-matter interactions. Many interesting phenomena, such as resonance fluorescence [1], the Hanle effect [2], lasing without inversion [3,4], electromagnetically induced transparency [5], coherent population trapping [6] and fast Rabi induced sideband emission [7] are just a few examples of important quantum optical effects. Alkali metal vapors are important in such experiments since these vapors are monatomic elements (however at ultrahigh densities, dimers and trimers start forming as well) and have the lowest ionization energies of the elements, which allows the use of lower frequency light for excitation.
Physics of electromagnetically induced chirality and anti-symmetric wave transmission
Published in Journal of Modern Optics, 2019
Rafi Ud Din, Xiaodong Zeng, Guo-Qin Ge, M. Suhail Zubairy
It has been widely investigated that optical properties of multi-level atomic media can be influenced by coherently driven fields. This results in quantum coherence which has lead to well-known phenomena such as electromagnetically induced transparency (EIT) (1, 2), lasing without inversion (3, 4) and negative refraction (5, 6). It leads to the enhancement of nonlinear optical responses (7) and has found tremendous applications in devices for subluminal and superluminal light propagation (8, 9) as well as for stopping (10) and storing optical beams (11).