Er³⁺ ion concentration effect on transient and steady-state behaviorin Er³⁺ ：YAG crystal

The effect of Er³⁺ ion concentration on transient and steady-state behavior in 45-nm Er³⁺ :YAG crystal is investigated. It is shown that by changing the signal field, the coherent field and the concentration of Er³⁺ ions in the crystal, the absorption, dispersion, and group index of the weak probe field can be adjusted. Also, it is found that the probe absorption occurs in the presence of population inversion and probe amplification is obtained in the absence of population inversion.