The analysis of optical scattering in double-heterostructure and five-layer heterostructure (GaAl)As/GaAs injection lasers

The optical-absorption loss in (GaAl)As/GaAs heterostructure lasers with narrow active layers and passive layers doped below5 × 10¹⁷cm-3should be less than 5 cm-1. Measurements which have been made on a variety of three- and five-layer lasers have seldom shown such low figures. Optical-scattering loss at imperfections in the heterostructure interface could account for the discrepancy. An analysis of the scattering in both three- and five-layer heterostructures is presented. Curves are derived relating the absorption coefficient with the dielectric-constant step at the Waveguide Wall, the active-layer thickness, and the magnitude of the roughness. Measured losses as high as 12 cm-1can be accounted for by a roughness amplitude of only 0.01 μm.