Thermal waveguiding in oxide-defined, narrow-stripe, large-optical-cavity lasers

The characteristics of oxide-defined, narrow-stripe large-optical-cavity (LOC) AlGaAs lasers are described. Compared with regular narrow-stripe double heterostructure (DH) lasers, the LOC version exhibits more narrowing of the near-field and far-field distributions, higher astigmatism, higher differential quantum efficiency, and higher incidence of sustained pulsations. We have found that these phenomena can be explained in terms of the formation of a thermal waveguide. There is often a striking similarity in characteristics of narrow-stripe LOC and degraded narrow- stripe DH lasers. We suggest that a thermal waveguiding effect is an important factor in determining the behavior of degraded semiconductor lasers.