Resonance fluorescence of a strongly driven two-level atom produces the Mollow triplet (1969): a central peak at the laser frequency ω_L and two sidebands at ω_L ± Ω̃. The sidebands are dressed-state transitions. At Δ=0, all three peaks have equal widths (γ/2, γ/2, γ).
The Bloch equations describe the density matrix of a two-level atom. Strong driving (Ω ≫ γ) dresses the atom–field states, creating Autler-Townes splitting. The coherent (elastic) peak vanishes above saturation; incoherent emission dominates. The spectrum is a direct probe of quantum fluctuations.