Abstract: A system and method for producing relatively square laser pulses derived from relatively Gaussian laser pulses. The system comprises a phase conjugate laser system that comprises a laser oscillator, an amplifying medium and a phase conjugate mirror having a nonlinear confined at a predetermined pressure. The mirror is adapted to truncate the front portion of an applied laser pulse. A plasma switch is disposed between the laser oscillator and the amplifying medium that has a gas confined therein at a predetermined pressure. The plasma switch and phase conjugate mirror cooperate to truncate the laser pulse to produce a laser pulse having a relatively square shape. Controlling the pressures in the plasma switch and phase conjugate mirror provides a means of controlling the formation of square-shaped laser pulses. In addition, a delay line may be employed in the system that is controllable in length that assists in controlling the truncation of the pulse in the plasma switch.