Matching of a stripe injection laser to an external resonator

Theoretical and experimental investigations of the characteristics of matching of a planar active waveguide to an external axially symmetric resonator are reported. The dependences of the threshold current on the external resonator length are obtained for stripe injection lasers with the waveguide amplification effect. These dependences are shown to be opposite for a resonator with a parallel beam in the external part and for a system with beam focusing by an external mirror. In the case of lasers with a dispersive external resonator the slopes of the dependences are sensitive to the spectral tuning of a selective element. It is shown that the observed characteristics of the dependences of the threshold pumping rate on the length of the external resonator are related to the change in the curvature of the wavefront of the field during the passage through the external part.