Spectral and squeezing properties of the resonance fluorescence of two coupled quantum dots forming an effective Λ-type three-level structure and connected with two normal metal leads are studied. We assume that one of the dots is driven by a strong light field and find that by modulating the bias voltage and the dot-lead coupling strengths, the electron can be selectively trapped in one of the two dressed states produced by the light field. The trapped electron possesses large coherence, and the resulting unbalanced dressed-state populations ...