Q-switching

Q-switching is a process used to enhance the power output of a laser source. Output energy of the laser decreases after Q-switching. A ruby laser before Q-switching produces pulses with energy 10 joules in one millisecond. After Q-switching, the pulse duration decreases to 10 nanoseconds. This increases the output power from a few kilowatts to a few gigawatts. In Q-switching process, the feedback by the mirrors is suppressed. During Q-switching, the rate of pumping should be faster than the spontaneous decay rate from higher energy level. Q-switching should be rapid with a Q-switch time around 10 ns. Two methods are normally adopted to achieve Q-switching. They are rotating mirror method and electro-optic method. In a rotating mirror method, one of the mirrors of laser resonant cavity is rapidly rotated. This rotation should be properly synchronized with pumping flash. In electro-optical Q-switching, Kerr and Pockels effects are utilized.