Abstract
This paper presents the first application of a modified confocal optical probing system to spatially-resolving picosecond charge-density modulation along the cavity of an AlGaAs semiconductor laser. The measurements show that the internal charge concentration overshoots and then clamps at the threshold level in response to an input current pulse. The amount of overshoot was found to be proportional to the current pulse amplitude, and appears to agree with previous theoretical analyses.