Abstract: The invention relates to the control of the spatio-temporal uniformity of a pulsed gas laser beam, especially generated by a high-power excimer laser. According to the invention, two raised lateral parts are provided on at least one of the discharge electrodes, said parts enabling the electrical discharge to be initialised at this level and to remain constantly stuck at this level after having spread over the entire surface of the electrode between said raised parts. In order to compensate for the lack of uniformity of the discharge created by the lack of uniformity of the electric field, the collimation mask of the preionisation X-rays is thinned from the edges thereof towards the centre thereof in order to progressively reinforce the preionisation from the outer level of the discharge to the centre of the same. The invention enables a discharge to be obtained, and thus a plasma, which are both spatially uniform and temporally stable.

Abstract: A laser surface method involves applying a laser beam treatment in one or several steps to a series of generally similar surfaces of given depth. Properties of the laser treatment are selected so as to change the physical state of each surface. Ellipsometry measurements are made in a region of the first surface before application of the laser beam treatment to the second surface, so as to obtain a physico-chemical characterization of the first surface. Both the laser beam application and the ellipsometry measurement are conducted under generally similar working conditions, so that the change of the physical state of each surface produced by the laser treatment can be controlled in a real time, in-situ, rapidly and nondestructively.

Abstract: A laser source has two or more laser units and coupling means for coupling the laser beams from each unit so as to deliver a resulting beam for treating a surface. Concurrently with the laser surface treatment, the characteristics of the laser beam from each unit are adjusted to produce a resulting laser beam with a time profile of energy optimally adapted to said laser surface treatment. Homogenizing means homogenize the energy distribution of the resulting laser beam, so that the energy and spatial distribution of said resulting laser beam are concurrently adapted for the selected surface treatment.