The invention relates to an optical amplifying medium comprising a liquid medium, having an organic ligand corresponding to the following chemical formula: the groups R1, R2 and R3 comprising halogenated chains and a rare earth ion. The advantage of using a liquid medium lies in the possibility of more easily discharging the heat within the amplifying medium. The present solution provides a formulation that furthermore makes it possible to have entities that are non-toxic contrary to those proposed in the prior art.