High-power fiber lasers drive noncontact-measurement techniques

Rayleigh-scatter-based profiler provides instantaneous measurements of spot size, focal-spot location, focal-plane shift in the propagation and lateral axes, and m2 and BPP measurements. This beam profiler, BeamWatch, can assess lasers that have power densities of 2 MW/cm2 or greater without requiring any optics or waveguides to be placed in the beam path. Because no optic interacts with the beam, there is no practical limit to observable power densities. The profiler uses a CCD camera to image the laser path over a distance of more than 25 mm as it propagates through focus. The camera frame rate permits the focal plane, and thus any focal-plane shift, to be continuously monitored in ≥40 ms intervals. The operator screen displays the beam caustic in false color, along with the initial and current focal plane location. Calculated results include m2, waist width, waist location, focal-plane shift, divergence, beam parameter product (BPP), power, and centroid location.