A handpiece having a shell for removably housing a cartridge with a window having a light source and a cooling circuit thereof as well as a cover. A light guide connects the light source to the surface of the skin. The position of the cartridge is defined by a base having cartridge connection members and by a guiding surface having one end corresponding to the base and sides defining lateral guide rails around the position of the light guide. The cartridge is in the form of a planar housing having one end bearing a transverse assembly plate provided with connection members homologous to those of the base, and the sides include guiding ribs interacting with the lateral rails.
