  Emission from a resonantly excited quantum emitter is a fascinating research
topic within quantum optics and a useful source for different types of quantum
light fields. The resonance spectrum consists of a single spectral line below
saturation of a quantum emitter which develops into a triplet at powers above
saturation of the emitter. The spectral properties of the triplet strongly
depends on pump power and detuning of the excitation laser. The three closely
spaced photon channels from the resonance fluorescence have different photon
statistical signatures. We present a detailed photon-statistics analysis of the
resonance fluorescence emission triplet from a solid state-based artificial
atom, i.e. a semiconductor quantum dot. The photon correlation measurements
demonstrate both 'single' and 'heralded' photon emission from the Mollow
triplet sidebands. The ultra-bright and narrowband emission (5.9 MHz into the
first lens) can be conveniently frequency-tuned by laser detuning over 15 times
its linewidth ({\Delta \nu} \approx 1.0 GHz). These unique properties make the
Mollow triplet sideband emission a valuable light source for, e.g.quantum light
spectroscopy and quantum information applications.
