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.
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