A new form of planar index-guided laser diode is demonstrated with a relatively thick (∼0.4 μm) native oxide employed to define the lateral optical waveguide (transverse to the laser stripe). Oxidation of high-gap AlxGa1−xAs in a ‘‘wet’’ ambient results in the transformation of most of the upper confining layer to a lower-index current-blocking native oxide outside of the active stripe. Planar quantum well heterostructure (QWH) AlxGa1−xAs-GaAs laser diodes fabricated by this process exhibit both optical and current confinement. Continuous 300 K threshold currents as low as 10 mA (uncoated facets) and kink-free single-longitudinal-mode operation are demonstrated for ∼2-μm-wide active region devices.