An acousto-optic modulator (AOM) is a device which can be used for controlling the power, frequency or spatial direction of a laser beam with an electrical drive signal.
Acousto-optic modulators find many applications:
- Q switching of solid-state lasers. The AOM, called Q-switch, serves to block the laser resonator before the pulse is generated. In most cases, the zero-order (not diffracted) beam is used under lasing conditions, and the AOM is turned on when lasing should be prohibited.
- AOMs for cavity dumping of solid-state lasers, generating either nanosecond or ultra-short pulses.
- AOM as a pulse picker for reducing the pulse repetition rate of a pulse train, e.g. in order to allow for subsequent amplification of pulses to high pulse energies.
- In laser printers and other devices, an AOM can be used for modulating the power of a laser beam. The modulation may be continuous or digital (on/off).
Main Acousto-optic modulation principles
AOM is based on the acousto-optic effect, i.e. the modification of the refractive index by the oscillating mechanical pressure of a sound wave.