Acquisition et exploitation quantitative des signaux issus de l'analyseur de faisceau LBA

Abstract
The present study is applied to laser beam analyser (LBA). The basic principles of this device have been described by Lim and Steen in 1982 and 1983 [l] [2] : in the LBA device, when a needle crosses the beam, a fraction of the radiation is reflected onto two pyroelectric detectors. The instrument is now very useful to characterize the power density distribution of a laser beam. A real time signals acquisition device has been made through an INTEL 320 computer. The crude analog signals (X and Y) of the LBA output are deformed, therefore, they don't exactly represent the true power distribution. Reconstitution of initial form by a numerical correction permits to use the signals with efficiency : the physical parameters of the beam can be defined with great precision (diameter, beam centre position), true energy distribution can be calculated by a volume integration as well. The whole corrections through a program on IBM PC is available ; after corrections, the signals are used to calculate the centre position, the beam radius (R_1/e2), its global power and the power density (W/cm²) in each point of the beam section.