A pulsed laser system includes a variable attenuator located in a secondary optical path bounded by a target surface and one or more reflective surfaces outside of the primary laser oscillator of the laser system. The variable attenuator isolates an output optical amplifier of the laser system from light reflected from the target during time periods between laser pulses. In some embodiments, the variable attenuator is synchronously controlled with the primary laser oscillator. In some other embodiments, the variable attenuator is controlled separately from the primary laser oscillator to shape the generated laser pulses.