Study of twisted beam symmetrization from laser diode bar

A principal drawback of high-power laser diode, which limits their applications such as pumping solid-state laser and fiber laser, is astigmatic brightness of output beam. The astigmatic beam emitted from laser diode bar is transformed into a beam with twisted symmetry by using a bifocal telescope and rotated cylindrical lenses. The beam widths, divergences and the beam parameter products of the symmetrized beam are nearly the same in x and y directions. The beam transformation was theoretically analyzed and experimentally studied. As an example, the symmetrized beam was used to pump solid state laser. The efficiency of the fundamental mode operation was improved compared with the result of untransformed beam pumping.