Figure 7.20 describes some of the methods for Q switching.

• Turning mirror at the end of the optical cavity - Only when the mirror is facing the other mirror, there is lasing. To increase the number of pulses per second, a special drum with many mirrors is turning. Thus for every turn of the drum, many pulses are emitted, since each mirror on the drum is facing the cavity separately.
• Electro-Optic transducer - Change the transmission through the device by electric voltage.
• Acousto-Optic transducer - Change the transmission through the device by acoustic signal.
• Saturable absorber - An absorber that becomes transparent when it reach saturation. It is usually a dye solution which prevents lasing by absorption. When the radiation arrives at a certain level, this absorber comes to saturation, and since it can no longer absorb radiation, it becomes transparent. At that moment lasing can occur, and all the stored energy inside the cavity is emitted as a single pulse.