= Solution
<Q-switching> stores excitation in a pumped <laser gain medium> while preventing oscillation, then rapidly changes the <optical cavity> from high loss, or low <quality factor>, to low loss, or high <quality factor>. The initially suppressed stimulated field can then grow rapidly from a seed and deplete a large <population inversion> in a short pulse. The resulting peak <power> is much higher than for continuous operation at the same average pumping rate. This is <energy> storage and release, rather than the phase locking of many longitudinal modes used in <mode locking>.
An active implementation uses a <Pockels cell> and a <polarizer>. An applied voltage makes the cell change the intracavity <polarization>, causing the <polarizer> to introduce sufficient loss to prevent lasing while pumping builds the inversion. Rapidly changing the voltage removes that loss and opens the high-Q state. The switching time should be short relative to the pulse build-up and depletion times. A <saturable absorber> provides an alternative passive Q switch: its absorption decreases as the intracavity intensity rises.
Back to article page
