Longitudinal pumping of lasers with multistripe laser diodes

The conventional method of focusing a multistripe laser diode to end pump a laser is collimating the beam, compensating the different beam divergencies parallel and perpendicular to the array by a cylindrical lens or a prism pair, and finally focusing the beam to a circular spot. We have developed an alternative arrangement consisting of a spherical and a cylindrical lens. In essence this method images object planes parallel and normal to the array differently. For a detailed discussion of the two focusing systems we assume that the pump beam consists of a linear array of Gaussian beams. Calculations of the laser threshold for both focusing methods are performed to compare the efficiency of the focusing arrangements. The experimental realization of our focusing arrangement to pump a Nd:glass laser with a multistripe diode yields a threshold of 62 mW and a slope efficiency of 22%. The theoretical predictions agree well with experimental data.