Zero-order transverse mode operation of GaAs double-heterostructure lasers with thick waveguides

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Abstract
Fundamental (TE00 and TM00) transverse mode operation has been obtained from stripe-geometry GaAs double-heterostructure injection lasers with optical waveguides which are 2 μm thick. Selection of the zero-order mode perpendicular to the junction plane is achieved by providing a spatially nonuniform gain distribution within the waveguide. The nonuniformity is realized by locating the p-n junction within the waveguide such that the ratio of the thicknesses of the p and n regions is 2/1. For this choice of gain profile, the electronic gain of the zero-order mode is greater than that for higher-order modes by an amount sufficient to overcome the higher mirror loss of the zero-order mode. Along the junction plane, the stripe-geometry configuration provides zero-order mode operation. As a result, pure fundamental mode operation has been obtained at current levels up to 2.2 times threshold. Measurements are also reported for the internal stimulated efficiency, the bulk loss, and the electronic gain at threshold of the zero-order mode relative to the higher-order modes. Single-ended pulse output powers as high as 0.7 W (4×106 W/cm2 at the mirror) have been obtained from AR-coated devices without observable mirror damage.