Two working modes of acousto-optic modulator

Two working modes of acousto-optic modulator
An acousto-optic modulator (AOM modulator) is a device that can modulate the intensity or deflect the angle of a laser beam without the need for any macroscopic moving parts. Its core principle is simple: excite sound waves in a transparent medium, use the density periodic changes caused by sound waves to form a diffraction grating, and thereby change the light passing through it.
1.After entering the Prague district, AOM modulator has two basic uses:
1.1Intensity modulation: fixing the RF frequency and changing the RF power. The change in sound intensity leads to a change in the depth of the grating, and the intensity of the first-order diffracted light changes accordingly. The simplest intensity modulation is a switch: when the RF is turned on, the first level light spot appears; RF off, the first level light spot disappears.
1.2Beam deflection/scanning: changing the RF frequency. The frequency change causes the wavelength of the sound wave to change, and the grating constant changes accordingly, resulting in a change in the diffraction angle. The laser beam will deflect within a very small angle range. Working in this mode typically involves calling for an optical deflector (AOD).
The essence of an acousto-optic modulator can be understood as a programmable diffraction grating, which uses radio frequency signals to control ultrasonic waves, ultrasonic waves to control grating parameters, and then gratings to control the direction and intensity of the laser. It has no macroscopic moving parts and can complete light switching, dimming, and small angle scanning at extremely high speeds. Although the cost is high and the deflection range is limited, there is currently no better alternative solution on the track of ultra high speed light control.
The advantages of AOM modulator are fast speed, no wear, and high precision, but it has not completely replaced mechanical solutions. The reason is very direct: the structure is complex, the price is high, the deflection angle is extremely small, and the overall efficiency is far lower than mechanical systems such as mirrors and motors. So in situations where speed requirements are not high, mechanical deflection is almost always a better choice. Only when the modulation speed reaches MHz or above and the mechanical structure cannot keep up, can acousto-optic devices truly be irreplaceable.