Abstract: A semiconductor laser diode includes a first buffer layer, a second buffer layer and an active layer sandwiched between the two buffer layers. The active layer contains dopant ions where the dopant ions are such that energy transfer between the unimplanted material in the active layer and the dopant ions implanted causes lasing action substantially at a single frequency characteristic of the dopant ions. The two buffer layers confine light emitted by the active layer. The second buffer layer is grown epitaxially on the active layer. In the preferred embodiment, the structure is made by first growing a thin second buffer layer epitaxially on the active layer. The dopant ions are then implanted into the active layer through the thin second buffer layer. The structure is heated to a high temperature to anneal the structure and to activate the dopants. The second buffer layer is then further grown to make it thicker so as to be more effective in confining the light emission in the active layer.