Coating for dfb/dbr laser diodes

Abstract

In DFB/DBR semiconductor diode lasers, competition may arise between the DFB (Distributed Feed-Back) mode corresponding to the period of the grid present and the FP (=Fabry-Perot) mode determined by the relative distance of the mirror surfaces, as a result of which the laser does not operate in one single mode. By providing an antireflex layer, this problem is suppressed, but other disadvantages are obtained, such as a large line width. However, by providing a phase layer on the antireflection coating, the operation of the laser in a single mode is combined with a comparatively narrow line width. Furthermore, a reflective coating can be applied to the phase layer. In this case, both the module and the phase of the effective reflection can be adjusted substantially independently of each other, as a result of which a narrow line width and SLM can be more readily combined. The antireflex coating, the phase layer and the reflective coating can be manufactured by means of not more than two materials having a suitable refractive index. Two particularly suitable materials are hafnium oxide and silicon dioxide, which can be applied to the mirror surfaces by means of the comparatively simple and attractive vapor deposition technique.