3719 Warren Avenue Bellwood,
Illinois 60104 USA






What is an Acoustic Optic Modulator AOM and How Does it Work?

Acousto-optic modulators (AOM) are used to modify the intensity of laser beams using electrical drive signals. Essentially, it works by changing the refractive index of crystal or glass material using sound waves oscillating under strain.

There are various acousto-optic devices, each offering different characteristics; AOM is among the more frequently encountered types.

The AOM consists of a Bragg cell

What is an Acoustic-Optic Modulator (AOM), and how does it function?

An AOM uses the acousto-optic effect to change and alter light frequency using sound waves, and is used across a range of applications including lasers for Q-switching, telecom signal modulation and frequency control in spectroscopy spectroscopy.

AOMs incorporate a Bragg cell, an acoustic refractive index grating. Usually composed of thin film bonded to photo-elastic medium such as tellurium dioxide or fused silica, its material selection depends on criteria like its figure-of-merit, elasto-optic coefficient, attenuation coefficient, sound velocity and transparency range.

An RF driver, typically a voltage controlled oscillator (VCO), produces the acoustic wave, which is then amplified before entering the AOM. A control voltage is then applied to alter how much RF power drives the AOM. For two-frequency methods, another VCO generates another signal that is attenuated before going to AOM.

Once we have configured the radio frequency (RF) power, we can measure angular displacement of first order beam using two distinct frequencies of radio frequencies, thus changing intensity of acoustic wave within AOM without altering output light beam amplitude.

For this demonstration, we employ a Ge AOM with an elaborate control box. A pair of Zener diodes generate a voltage Uin that is converted by an amplifier into an inverted voltage Uout before being adjusted using variable offset Uoff for optimal operation and maintaining constant total radiofrequency power usage by AOM.

Adjustment can be accomplished by altering the control voltage via an electronic circuit (shown in detail in Appendix), then sending this voltage through to AOM where it will be reflected back onto RF driver.

An AOM may operate at either a higher or lower frequency depending on its input beam diameter and desired bandwidth; typically for higher bandwidth signals, lower frequency AOMs are often preferred.

The Bragg cell consists of a piezoelectric transducer

An AOM (acousto-optic modulator) is a device that uses piezoelectric material to convert mechanical motion into an electrical signal, typically for use in high frequency RF transmission applications. AOMs can be made using different materials, including quartz crystals with piezoelectric properties and Rochelle salt for manufacturing purposes.

Acousto-optic modulators are versatile devices used for many different purposes, including Q-switching, modelocking, cavity dumping and laser Doppler vibrometry. Their birefringent phase matching and planar acoustic beam steering techniques create large modulation bandwidths at their RF outputs to produce maximum modulation bandwidths with their modulations outputs.

A piezoelectric transducer is a piezoelectric element that utilizes the inverse piezoelectric effect to convert mechanical movement to an electrical signal. This process is reversible; when an electric voltage is applied, its dimensions change, altering its composition.

Piezoelectric materials can be produced using many types of materials, from quartz crystals and ceramics to solid state piezoelectric compounds specifically formulated to exhibit piezoelectric properties.

These piezoelectric materials can be produced in multiple ways and shaped to suit various applications, typically including silicon, oxygen and calcium as examples of piezoelectric materials.

An advantage of using piezoelectric materials as transducers is their versatility in operating at various frequencies ranging from MHz to GHz, making the device suitable for many different uses such as ultrasound sonar echolocation, distance sensors, flow sensors and level sensors.

Piezoelectric materials also have the advantage of being applicable in environments with a lot of vibration, helping devices operate more reliably and precisely.

However, piezoelectric transducers can become damaged if not properly maintained and this could result in costly repairs if left to accumulate dust and debris. Therefore it is vital that they are regularly kept free of dirt.

Bragg Cells have quickly become a go-to product in the acousto-optic modulation industry over the past several years, due to rising demand and technological innovations that have provided increased performance and an enhanced user experience.

The piezoelectric transducer consists of an RF driver

Piezoelectric transducers are sensors based on the piezoelectric effect, which converts mechanical pressure into an electrical signal. Piezoelectric sensors can be used to measure various parameters including acceleration, force, temperature and strain.

These devices can be found in numerous applications, from microphones and electric lighters to doors and microphones for microphones. Furthermore, they’re often utilized within hospitals or airports.

Piezoelectric systems typically utilize an RF driver to convert electric current to an acoustic pressure field for various applications, including phased array microphones and ultrasound equipment.

Contrary to other types of sensors, piezoelectric devices do not require external power or force for operation, making them suitable for use on airplanes and in restaurants among other environments.

Op amps are often chosen to power piezoelectric transducers as their RF driver, due to their ability to keep frequency output within safe levels for piezoelectric devices which are vulnerable to voltage changes and can help ensure low enough frequency output that won’t damage them.

Once installed, devices powered by drivers can be powered from a variety of sources ranging from car engines to mobile batteries. Selecting the appropriate power source for your application can make an immense difference in its effectiveness.

Consideration must also be given to the size of transducers used. Larger transducers require higher voltage levels in order to generate equivalent forces as smaller ones.

To choose the appropriate transducer size for your application, consider both the size and force requirements for animating an object. This will enable you to choose both device size and driver type accordingly.

A piezoelectric transducer is composed of piezoelectric material, which produces electric charge when subjected to pressure or force. Common examples include quartz or Rochelle salt; other options may include lithium sulphate and ethylene diamine tartarate.

The RF driver consists of an RF amplifier

An RF amplifier is an electronic device used to convert low-powered radio-frequency signals to higher power frequencies, making them suitable for use in various radio transmitters and acoustic devices like an AOM.

An RF power amplifier’s primary objective is to increase output signal levels as much as possible without impacting performance, typically done by modifying frequency and intensity settings of its input RF signals. Furthermore, its design incorporates temperature and load considerations for its intended application.

Designing an RF amplifier requires fulfilling several specifications, including gain, output power, bandwidth, input/output impedance matching and heat dissipation. Furthermore, its design must accommodate for short circuits or misconnections in its component parts.

An effective means of creating an RF amplifier is through using a transistor. While these devices are highly efficient, their non-linearity requires them to be set up with a tank tuned circuit to reduce unwanted harmonics.

They produce very high power at low input/output frequencies, making them suitable for radio transmitters or servo motor controllers that require very high levels of output power. However, to produce maximum output they require a power supply capable of handling their high current requirements.

Some RF power amplifiers incorporate a power switch or envelope tracking modulator designed to isolate the amplifying of RF input from power consumption within the amplifier’s circuit, eliminating excess energy while guaranteeing proper signal amplification at all times. This helps ensure optimal operation while eliminating wasteful consumption.

G&H offers an assortment of drivers designed to control an AOM. These units come in different formats and can be operated via either analog or digital interfaces for convenient operation.

These devices can be used to drive various AO devices, including cavity dumpers, deflectors, fiber-coupled modulators, mode lockers, pulse pickers, q-switches, and tunable filters. Their driver can be controlled either analogically or digitally and allows you to configure its frequency, amplitude, and phase output signal accordingly.

The RF driver can be either a single- or dual-channel amplifier. This allows it to generate an array of frequencies simultaneously – an essential feature for modulation applications as it provides variable drive frequencies which can be tailored specifically to drive each AO device being driven.
Scroll to Top