Abstract

Enhanced lateral mode stability and reduced output beam divergence in the plane of the active layer have been recently observed with narrow stripe gain¹ and index guided² diode lasers with a cylindrically concave etched facet. A major consequence of this geometry is the focusing of the intracavity beam after reflection on the facet. In narrow stripe lasers, this improves the matching of the fundamental lateral mode with the narrow lateral gain profile. The radius of curvature of the facet has a major influence on lateral mode characteristics. A careful analysis is therefore required to estimate the best design parameters prior to fabrication. We used the beam propagation method since it is well suited as a numerical tool for the investigation of these nonsymmetric resonators with waveguiding geometries. We found that the beam divergence may be significantly reduced, and this reduction is generally accompanied by a lower oscillation threshold. Although the calculated lateral mode distributions are different from those obtained with conventional gain guided lasers, the excellent lateral mode discrimination proper to these devices seems to be preserved with the concave facet.

© 1989 Optical Society of America