An acousto-optic deflector (AOD) is a device that uses an acousto-optic effect to deflect a beam of light. The acousto-optic effect is the interaction of light with a sound wave, which can cause the light to be diffracted or scattered. In an AOD, the sound wave is generated by an electrical signal that is applied to a piezoelectric transducer, which converts the electrical signal into an ultrasound wave. The ultrasound wave then propagates through a material that exhibits the acousto-optic effect, such as a crystal or glass, and the light is diffracted as it passes through the material.

The center frequency of an AOD is the frequency of the ultrasound wave that is generated by the piezoelectric transducer. The center frequency determines the wavelength of the ultrasound wave, which in turn determines the angle at which the light is diffracted. By matching the Bragg angle, which is the angle at which the light is diffracted with maximum efficiency, with the driving frequency, you can achieve the highest diffraction efficiency at that frequency.

The center frequency is an important parameter of an AOD, as it determines the range of frequencies over which the device can operate effectively. In general, the higher the center frequency, the wider the range of frequencies over which the AOD can operate. However, the center frequency also affects the performance of the AOD in other ways, such as the maximum diffraction efficiency that can be achieved, the size and shape of the diffraction pattern, and the response time of the device. Therefore, it is important to carefully consider the center frequency when selecting an AOD for a particular application.

Hi, Zhentao She

Adding my comments to the answer above.

There are multiple factors which could influence center frequency in AOD or any other AO devices.

One of the most important factors - material or crystal, which is a core of AO device. Acoustic wave's propagation velocity and attenuation are 2 critical parameters bond to material structure and operating frequency to consider when designing AO device, since these 2 could affect diffraction efficiency, depending which cut is used in the AOD.