Native oxide technology is used to fabricate long wavelength (lambda approximately 1.3 mum) InAlAs-InP-InGaAsP quantum well heterostructure laser diodes with a buried oxide undercutting and constricting the ridge-waveguide active region. The buried native oxide of InAlAs constricts the current and reduces edge and surface losses. Data are presented showing threshold currents as low as approximately 140 mA for approximately 13-mum-wide stripes (L approximately 750 mum), with maximum continuous wave output powers as high as approximately 225 mW/facet and external differential quantum efficiencies up to 67% (300 K, uncoated facets).