High power electrically pumped VECSELs and arrays

Abstract

VECSELs are characterized by an outstanding brightness of 100kW/mm²/sr and a small spectral width. Electrical pumping and the potential to combine many emitters in arrays allow for highly integrated and easy to manufacture laser sources which can be scaled towards high power. This almost ideal value proposition is affected by the penalty in efficiency which reduces the output power from VCSELs towards multimode VECSELs and finally single mode VECSELs. The root causes for this lower efficiency are optical losses in the extended cavity, a mismatch of pump and mode profile and losses related to the oxide aperture which is used for current confinement. The reduction of losses requires a careful design of spatial doping distributions in the epitaxially grown layers as these losses have to be balanced against the requirement of low electrical resistance across the many hetero-interfaces in the DBR mirrors. The mismatch of pump and mode profile and the aperture related losses are addressed by an improved current injection enabled by a tailored electrical contact. In this paper optimized structures will be presented which enable a significant increase of efficiency and output power towards more than 150mW in a single mode and more than 300mW in multimode operation. The optical concept of the extended cavity can use a plane mirror in the simplest case thus facilitating the power scaling in arrays with many individual VECSEL apertures combined on a single chip.