FABRICATION AND CHARACTERISTICS OF GAIN-COUPLED DISTRIBUTED FEEDBACK SEMICONDUCTOR-LASERS WITH A CORRUGATED ACTIVE LAYER

A new distributed feedback (DFB) semiconductor laser structure has been proposed where pure gain coupling can be realized. At the same time, the fabrication procedure of this structure has been proposed, which makes use of a special feature of organometallic vapor phase epitaxy. Lasers of this structure were fabricated to show the validity of the proposal. Coupling coefficients of DFB lasers have been calculated considering the gain-coupling component for the first time. Using the results, a DFB laser has been designed to obtain pure gain coupling. The parameters of the actual structure observed under a scanning electron microscope showed good agreement with those designed. We achieved device characteristics that were predicted for purely gain-coupled DFB lasers. For greater gain coupling and lower threshold current operation, an optimization mainly on the Al composition of a so-called pattern-providing layer and the thickness of the active layer in the new structure has been carried out. As a result, a low threshold current of 17 mA and a high side-mode suppression ratio of 45 dB have been accomplished.