Symmetric separate confinement heterostructure lasers with low threshold and narrow beam divergence by m.b.e.

By optimising the layer structure in a symmetric separate confinement heterostructure laser, and by using molecular beam epitaxy to grow the very thin active layer (~500 Å) needed, very low current threshold densities of ~600 Å/cm2 without reflectance mirror coatings and very stable narrow beam divergence of ¿¿~30° and ¿¿~4° were reproducibly obtained.