Abstract: A semiconductor laser powered by both a dc current and an rf current. Varying the level of the dc current changes the shape, power and timing of a pulse emitted by the laser. The laser emits pulses in response to the leading or rising edge of the rf current. The time between the leading edge of the rf current and the emission of the pulse has been found to vary with the level of the dc current. Correspondingly, the shape and power of the emitted pulse also varies with the varying of the dc current. Further the shape, power and timing of the pulse varies with variations in the rf current. The present invention varies the dc and rf current to a laser, to vary the timing of the pulses from the rising edge, while maintaining the shape and power of the pulses substantially constant for all different variations in timing.