Spectroscopy of the excited $D_s^+$ mesons

The discoveries of the $D^∗_{s0}$(2317)$^+$ and $D_{s1}$(2460)$^+$ mesons challenge our understanding of quantum chromodynamics. After almost 20 years, the nature of these hadrons is still subject of debate and many models have been proposed to explain their unexpected masses: standard charmed-strange mesons, $DK$ molecules and tetraquarks. The LHCb experiment has studied the production of excited $D^+_s$ meson in prompt proton-proton collisions and from $b$-hadron decays. Precise measurement of their properties and observation of new $D^+_s$ states have been reported. The latest results on the spectroscopy of the charmed-strange mesons and the prospect to investigate their nature will be presented.