Periodic gain structures for vertical cavity surface emitting lasers

In this work we present material characterization of active material consisting of one and two (periodic gain, PG) stacks of quantum wells, respectively, for 1.55 μm vertical cavity surface emitting lasers (VCSELs). The goal was to increase the round-trip gain in the vertical cavity in order to overcome the losses. The material characterization was performed by processing it into edge emitting gain-guided lasers. The periodic gain structure turned out to increase the overall output power by a factor of 1.5-2 as well as the quantum efficiency and T0 from 37 to 78 K. Since the single stack was later also employed successfully in electrically pumped RT-pulsed VCSELs on InP/GaInAsP mirrors, the PG structure is a promising concept to reach lower-threshold, higher-output power and cw operation.