Single transverse-mode filtering utilizing ion implantation: application to 1.48-μm unstable-cavity lasers

We demonstrate the relevance of ion implantation of the multiple quantum-well active layer in unstable-cavity lasers as a means of efficiently filtering the parasitic higher order waves by introducing additional propagation loss within the cavity. Several H/sup +/ implantation schemes are proposed and a comparison is successfully made of experiment to a beam propagation method (BPM) model on the basis of modal behavior. The work finally resulted in improved single transverse-mode behavior of those lasers: more than 1.3 W CW of diffraction-limited power at 1.48 μm was then obtained utilizing a two-step implantation process.