Properties of MO-CVD-grown GaAs/GaAlAs lasers as a function of stripewidth

Gain-guided lasers grown by metal-organic chemical vapor deposition (MO-CVD) are studied experimentally and theoretically with conducting stripewidth s as a variable. Stripe geometry lasers of 2, 4, 6, and 8 μm width, delineated by shallow proton implantations. Are very uniform relative to those grown by liquid-phase epitaxy (LPE). Measured and calculated thresholds are virtually independent for s for the low-spreading resistance devices studied, whereas differential quantum efficiency decreases monotonically with diminishing s. Computed charge density distributions peak most sharply for s=2 μm, and only for s-8 μm do they become sufficiently broad so that kinks occur below 15 mW output power levels. Spectra spread inversely with s and shift to shorter wavelengths as s is decreased. Measured and calculated far-field radiation patterns agree well and change continuously from a single central-peaked lobe for s=8 μm to one with two lobes at s=2 μm. Near-field intensity patterns depend only weakly on s between 2 and 8 μm, but computed phases vary greatly with s and, as a result of charge-induced antiguiding, account directly for the far-field results.