Laser Diode Beam Equalized into Circular Shape

Using the twist effect of graded-index fiber optics, scientists at Mitsubishi Electric Corp. in Amagasaki, Japan, have converted an asymmetric laser diode beam into a circular one. Beam qualities went from M² of 500 in the slow axis and 4 in the fast axis to M² of 175 for the circular configuration. Using a 5-m-long fiber with a 1200-µm core diameter, coupling efficiency from fiber input to output was 92 percent for the circular beam. The researchers say the beam-equalizing technique will work for a single array as well as for stacked high-power diode arrays. They reported their work in the Nov. 20 issue of Applied Optics.