Constricted double‐heterojunction (CDH) lasers have been prepared in a double‐dovetail channel structure, which consistently provides cw fundamental‐mode operation. Oscillation in both single lateral and single longitudinal modes (spectral halfwidth <0.09 A˚) is obtained at drive currents 50–100% above threshold and to cw power levels as high as 12 mW. ’’Kinkless’’ power‐current curves at 20 and 70°C have been obtained from all lasers prepared to date to power levels close to that at which degradation occurs (∼30 mW cw at 20 °C for a 3–4‐&mgr;m‐wide lasing region). Threshold currents of 55–75 mA and external differential quantum efficiencies (one facet) of 15–17% are obtained from 120–150‐&mgr;m‐long diodes with a reflector on one facet. Threshold current ratios as low as 1.26 have been measured between 20 and 70 °C.