Amplification without inversion controlled by tuned coupling field

Amplification without inversion (AWI) is discussed in a lambda three level system where a coupling field interacts with two separate optical transitions between two ground state hyperfine levels and an excited state level. Both electromagnetically induced transparency (EIT) and spontaneous radiation induced coherent dip are obtained, and AWI is observed in the EIT window by tuning the excitation frequency of the coupling field to satisfy certain conditions. The results show that, there is energy transfer between EIT and spontaneous radiation induced coherent dip, and when AWI is observed, there is no population inversion between the ground state hyperfine levels and the excited state level, but population inversion between the two ground state hyperfine levels.