Low threshold current planar buried heterostructure lasers with close spatial and large spectral separation

In this work we report a novel technique for achieving extremely closely spaced laser devices that may have nearly arbitrarily large, but well controlled, wavelength separation between the emitters. The basic concept underlying this device strategy, which we refer to as the stacked active layer (SAL) technique, is described. An initial set of epitaxial layers is grown, containing two or more active regions immediately adjacent to each other for the two or more wavelengths of operation that are desired. The active regions are stacked in the order of increasing emission wavelength, or decreasing energy bandgap as one moves upward from the crystal substrate. Patterned etching is used to remove the longer wavelength active regions in those areas where it is desired to have the shorter wavelength active regions operate. This patterned etch is followed by a regrowth of the upper cladding layer over all devices