The finite bandwidths of the driving and the probe field decrease the gain and change the value of the index of refraction, especially of the driving field.

• 激发场线宽破坏了原子的相干性，使介质的增益下降并改变了折射率的大小，探测场的线宽使介质的探测增益谱及折射率谱的分辨率下降。