Effect of one-photon detuning on light speed reduction in a three-level A-type atomic system

We have observed the reduction of group velocity of light via electromagnetically induced transparency (EIT) and measured the dependence of pulse delay on the one-photon detuning in a three-level A-type atomic system. The results show that due to the effect of Doppler broadening the light speed reduction is significant in a range of ± 600 MHz one-photon detuning. Under the condition of considering the Doppler shift of frequency, the pulse delay as a function of the one-photon detuning is numerically calculated. The experimental measurements are in good agreement with the theoretical results. These researches provide theoretical and experimental references for controlling the group velocity of light by means of one-photon detuning.