https://doi.org/10.1140/epjd/e2009-00287-1
Gain-assisted giant Kerr nonlinearity in a 
-type system with two-folded lower levels
1
Department of Physics, East China Normal University,
Shanghai 200062, P.R. China
2
Key Laboratory of Optical and Magnetic Resonance
Spectroscopy, and Department of Physics, East China
Normal University, Shanghai 200062, P.R. China
3
Centro de Física Teórica e Computacional, Universidade de
Lisboa, Complexo Interdisciplinar, Avenida Professor Gama Pinto 2,
Lisboa 1649-003, Portugal
4
Department of Physics, Zhejiang Normal University,
Zhejiang 321004, P.R. China
Corresponding author: gxhuang@phy.ecnu.edu.cn
Received:
16
June
2009
Published online:
17
November
2009
We propose a four-level Λ scheme with a one-mode active Raman gain core and two-folded lower levels to obtain new linear and nonlinear optical responses. We show that this scheme is fundamentally different from that based on electromagnetically induced transparency (EIT). Firstly, it is gain-assisted and thus capable of eliminating all attenuation of probe field. Furthermore, due to the quantum interference effect introduced by a coupling field a gain doublet appears in gain spectrum, and hence the distortion of the probe field during propagation can be effectively avoided. In addition, in such system a large and rapidly responding Kerr nonlinearity can be produced, which is much (more than 10 times) larger than that obtained in the EIT-based scheme with the same energy-level configuration.
PACS: 42.65.An – Optical susceptibility, hyperpolarizability / 42.50.Gy – Effects of atomic coherence on propagation, absorption, and amplification of light; electromagnetically induced transparency and absorption / 42.65.Hw – Phase conjugation; photorefractive and Kerr effects
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2009
