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Chinese Physics Letters

Experimental Evidence of Radiation Amplification Without Population Inversion in Sodium Atoms

Gao Jinyue, Guo Chuan, Jin Guangxu, Guo Xinzhen, Wang Qingwen, Zhang Hanzhuang, Jian Guang Zhao, Yun Jiang, Wang Dezhong, Jiang Dongmei

Published Nov 1, 1992• 0 citations
Publisher

Abstract

We have demonstrated a radiation amplification without population inversion in sodium according to a four-level model, which was recently proposed by Norducci et al. The amplified radiation signal at 589.0 nm has been observed when an intense coherent driving field at 589.6 nm was on and an incoherent pumping process from the ground state 3 S 1/2 to 3 P 3/2 excited state was operating.

DOI
10.1088/0256-307x/9/11/007

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We have demonstrated a radiation amplification without population inversion in sodium according to a four-level model, which was recently proposed by Norducci et al. The amplified radiation signal at 589.0 nm has been observed when an intense coherent driving field at 589.6 nm was on and an incoherent pumping process from the ground state 3 S 1/2 to 3 P 3/2 excited state was operating.
We present a quantitative study of radiation amplification without population inversion based on models recently proposed by Harris [Phys. Rev. Lett. 62, 1033 (1989)]. We discuss both two-level and three-level arrangements in terms of the density matrix. Our calculations, which are fully time dependent, incorporate an incoherent pumping mechanism that is essential for amplification. We discuss in detail the range of and conditions on atomic parameters for which amplification is possible. Its feasibility is demonstrated through the direct calculation of the change of the intensity of a probe beam interacting with the atom.
We show that in a four-level atomic system with electromagnetically induced transparency, a coherent pump field can induce light amplification without or with population inversion. As the pump field intensity increases, the atomic system evolves from normal dispersion and amplification without population inversion into anomalous dispersion and amplification with population inversion. We report an experiment on light amplification in cold rubidium atoms and present experimental measurements that agree with theoretical calculations based on the four-level model system.
We show that in a four-level atomic system with electromagnetically induced transparency, a coherent pump field can induce light amplification without or with population inversion. As the pump field intensity increases, the atomic system evolves from normal dispersion and amplification without population inversion into anomalous dispersion and amplification with population inversion. We report an experiment on light amplification in cold rubidium atoms and present experimental measurements that agree with theoretical calculations based on the four-level model system.
We propose a new four-level atomic model for achieving light amplification at a short wavelength, where direct incoherent pumping into the top level is avoided by the advantage of coherent pumping. In this model, the lower level of the probe transition is an excited state but not the usual ground state. By analytical as well as numerical calculations, we find that the probe gain, either with or without population inversion, which depends on the relation between spontaneous decay rates γ42 and γ21, can be achieved with proper parameters. We note that the Raman scattering gain always plays an important role in achieving the probe amplification.
We propose a new four-level atomic model for achieving light amplification at a short wavelength,where direct incoherent pumping into the top level is avoided by the advantage of coherent pumping.In this model,the lower level of the probe transition is an excited state but not the usual ground state.By analytical as well as numerical calculations,we find that the probe gain,either with or without population inversion,which depends on the relation between spontaneous decay rates γ42 and γ21,can be achieved with proper parameters.we note that the Raman Scattering gain always plays an important role in achieving the rpobe amplification.