Effects of drive current upon defect distribution scan features in multi-longitudinal mode semiconductor lasers

Defect distribution (D²) scans calculated from semiconductor lasers at several values of drive current exhibit peaks associated with internal defects. The peak heights vary linearly with drive current in the regime far below threshold. Near threshold, the heights exhibit a sharp maximum at a critical current and decline at larger currents. The critical current is approximately equal to threshold for defects in the cavity interior, and less than threshold for defects located near one of the facets. A rate equation model accounts for this behavior and predicts values of drive current to obtain optimum peak height and optimum spatial resolution on internal gain anomalies