Polarization-dependence in multiquantum well lasers and semiconductor optical amplifiers: probing interwell transport effects

Summary form only given. The advantages and opportunities associated with the use of multiple quantum wells (MQWs) in semiconductor laser and semiconductor optical amplifier (SOA) active regions are accompanied by challenges. In a system with many wells separated by spatially thick or energetically high barriers, injected nonequilibrium carriers may become nonuniformly distributed among the wells. The subject of nonuniform carrier density distributions has attracted significant attention because it results in degradation in both static and dynamic performance: increased threshold current, above-threshold efficiency roll-off, lowered dynamic performance and worsened chirp. While the mechanisms underlying the problem of interwell carrier density nonuniformity have been clarified via numerical modeling, the phenomenon remains to be observed directly via experiment. We propose a method of using the difference in the dependence of TE vs. TM modal gain on nonuniformity of carrier density as a direct experimental probe of interwell transport effects. We illustrate the proposed mechanism: due to the difference in the spatial configurations of TE and TM optical modes, the TE and TM modes sample differently the effects of a nonuniform distribution of carriers among the wells.