Plasma generator with a slot antenna

A plasma generator comprising a propagation chamber (10) propagating an electromagnetic radiation, and a plasma-generating chamber (20) associated with the propagation chamber (10); said propagation chamber (10) has a passage region (12) of increasing width on moving away from the entrance region (11) for insertion of the electromagnetic radiation into the propagation chamber (10). The passage region (12) enables an at least partial passage of the electromagnetic radiation towards the plasma-generating chamber (20).