A carrier for treating photonic devices such as laser bars is provided with a recessed formation with a web surface for supporting the photonic device in contact therewith as well as at least one side surface forming an abutment surface for engaging a respective end facet of the photonic device. The photonic device is arranged in the recessed formation so that the lower surface of the photonic device is masked with respect to the treatment source, while at least one end facet of the photonic device engages at least one side surface by leaving exposed a surface to be treated. A protection member is placed in contact with the upper surface of the photonic device and the carrier with the photonic device arranged therein is exposed to the treatment source. The treatment is thus effective substantially exclusively on the surfaces of the end facets to be treated.