Many laser beams have a Gaussian intensity distribution, so applications that require a flat profile demand techniques that broaden or shape the beam, but also that waste some of the initial energy or create interference in the output. Reporting in the Nov. 1, 2000, issue of Applied Optics, a team at Paul Scherrer Institute in Villigen, Switzerland, has developed a mechanical method based on simple rotating shutters that avoids these problems.

Like degaussing plates, the shutters flatten the intensity distribution of a laser beam by absorbing energy at its center. Mounted on a ring that revolves around the beam, the shutters do, however, produce some irregularities at the center of a target because of the diffraction effects at their edges.