Measurement of spatial distribution of long-wavelength radiation from GaAlAs injection lasers

Present BTL injection lasers being produced for optical communication systems exhibit luminescence peaks at 1.5 eV (0.83 μm), 1.35 eV (0.92 μm) and 1.0 eV (1.25 μm). Examination of the spatial distribution of this radiation within the DH-laser diode has shown that the edge (1.5 eV) emission is confined to the active region, as expected, but the 1.35-eV radiation is divided between the active region and the substrate while the 1.0-eV radiation originates predominantly within the substrate. This result, in conjunction with recent work on laser aging, suggests that slow degradation of lasers may be due to a mobile impurity or defect originating in the substrate material on which the laser structure is fabricated.