Constricted doublehyphen;heterojunction (CDH) lasers have been prepared in a doublehyphen;dovetail channel structure, which consistently provides cw fundamentalhyphen;mode operation. Oscillation in both single lateral and single longitudinal modes (spectral halfwidth 0.09 Aring;) is obtained at drive currents 50ndash;100percnt; above threshold and to cw power levels as high as 12 mW. rsquo;rsquo;Kinklessrsquo;rsquo; powerhyphen;current curves at 20 and 70deg;C have been obtained from all lasers prepared to date to power levels close to that at which degradation occurs (sim;30 mW cw at 20thinsp;deg;C for a 3ndash;4hyphen;mgr;mhyphen;wide lasing region). Threshold currents of 55ndash;75 mA and external differential quantum efficiencies (one facet) of 15ndash;17percnt; are obtained from 120ndash;150hyphen;mgr;mhyphen;long diodes with a reflector on one facet. Threshold current ratios as low as 1.26 have been measured between 20 and 70thinsp;deg;C.
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