Observation of the population inversion of erbium ion states in Si/Si1−xGex:Er/Si structures under optical excitation

In this work we present the results of theoretical analysis and experimental studies carried out for Si/Si1−xGex:Er/Si structures considered as the candidates for a laser realization. Analysis of the electromagnetic modes distribution and parameters of Si/Si1−xGex:Er/Si waveguides enabling strong localization of the optical modes in the active Si1−xGex:Er layers is given. The Si/Si1−xGex:Er/Si structures in question were grown by the method of sublimation MBE in germane gas atmosphere. The capability of such a method for producing effectively emitting Si/Si1−xGex:Er/Si structures has been demonstrated. The photoluminescence intensity of the structures produced is comparable with that determined for the uniformly doped Si:Er layers with the external quantum efficiency ∼0.4%. We show the possibility to achieve the population inversion of Er3+ ion states in Si/Si1−xGex:Er/Si structures under optical excitation. The population inversion of Er3+ states in these structures sets in at the pump density of ∼0.2 W/cm2 and reaches its maximal value at ∼4 W/cm2, where the concentration of Er3+ ions being inversely populated amounts to ∼80% of the total concentration of optically active Er ions.