%A Yang Li-Jun(杨丽君), Zhang Lian-Shui(张连水), Zhuang Zhong-Hong(庄仲红), Guo Qing-Lin(郭庆林), and Fu Guang-Sheng(傅广生) %T Spectral feature with sub-natural linewidth due to quantum interference in a four-level system %0 Journal Article %D 2008 %J Chin. Phys. B %R 10.1088/1674-1056/17/6/034 %P 2147-2151 %V 17 %N 6 %U {https://cpb.iphy.ac.cn/CN/abstract/article_109913.shtml} %8 2008-06-20 %X This paper studies the narrow spectral feature appearing in a four-level system coupled by two strong coherent fields and probed by a weak laser field. The linewidth is examined as a function of the Rabi frequencies of coupling fields, and the result is explained by using the dressed-state formalism.