Method for narrowing the directional pattern of an InGaAs/GaAs/AlGaAs multiwell heterolaser

A semiconductor laser with a new waveguide is developed. It allows significant narrowing of the directional pattern (to 4$^\circ$ in the plane perpendicular to the $p$–$n$ junction). In the used waveguide, the minimum excess of the effective refractive index $n_{\operatorname{eff}}$ of the excitation mode over the substrate refractive index $n_{\operatorname{s}}$ ($n_{\operatorname{eff}}$–$n_{\operatorname{s}}\ll$ 1) is provided by selecting the thickness of Al$_{0.3}$Ga$_{0.7}$As confinement layers, which significantly increases the waveguide mode size and leads to directional-pattern narrowing.