Patent ID: 7817701

Claim:
An active element for a laser source, comprising: an elongated bar with reflective lateral surface, doped to be able to absorb at least a pumping beam being propagated at least approximately longitudinally in said bar in order to amplify at least a laser radiation also being propagated longitudinally, said bar in operation being the source of spurious laser emissions; and a jacket in contact with said lateral surface of said bar and presenting a refractive index smaller than that of said bar, wherein: in said reflective lateral surface of said bar, in a portion of said bar in which only a weak pumping beam flux passes, there is at least one dull-ground diffusing zone able to interrupt the paths of spurious laser modes being propagated in said bar by total internal reflections on said lateral surface; said jacket is able to reflect at least 80% of said pumping beam in said bar; and the length and the doping of said bar are such that the fraction of the energy of said pumping beam, absorbed by said bar, is at least equal to 80%.