The properties of double heterostructure lasers with very narrow active regions

Double heterostructure Ga x Al 1− x As-GaAs-Ga x Al 1− x As injection lasers have been made by multilayer solution epitaxy. Active region widths of less than 0·2 μm have been obtained, yielding threshold current densities down to 1000 A cm −2 at 300 K, with incremental efficiencies up to 50%. The results are all in reasonable agreement with the theory of optical waveguides, although some quantitative discrepancies may be due to imperfect knowledge of the experimental conditions. Emission polar diagrams became narrower when the width of the active region was decreased below 0·6 μm, showing that there was significant penetration of the optical field into the boundary regions when the optical waveguide was narrow.