AOM (Acousto-Optic Modulator)

By virtue of having no moving parts our acousto-optic modulators (AOMs) are able to amplitude modulate a laser beam at very high speed. For example modulation bandwidths in excss of 50MHz are readily achievable.

In an AOM a laser beam is caused to interact with a high frequency ultrasonic sound wave inside an optically polished block of crystal or glass (the interaction medium). By carefully orientating the laser with respect to the sound waves the beam can be made to reflect off the acoustic wavefronts (Bragg diffraction). Therefore, when the sound field is present the beam is deflected and when it is absent the beam passes through undeviated. By switching the sound field on and off very rapidly the deflected beam appears and disappears in response (digital modulation). By varying the amplitude of the acoustic waves the intensity of the deflected beam can similarly be modulated (analogue modulation).

It is usual to choose the deflected beam as the one that is used in the optical system because it can be switched on and off with high extinction ratio (typically >40dB) and intensity can be varied from zero to more that 85% of the incident beam. The rate at which the beam can be modulated is governed by the time it takes the acoustic wavefronts to traverse the laser beam, which depends on the beam diameter and the acoustic velocity in the interaction medium.

The sound waves are generated by a transducer, usually a thin wafer of lithium niobate, that is bonded onto the interaction medium using a highly efficient cold-weld metallic bonding process. When a high frequency electrical signal is applied to the transducer it vibrates, generating the acoustic wave. The signal is derived from an RF driver, which generates a high frequency carrier that is itself modulated by an analogue or digital input signal.

Principal applications for AO modulators are pre-press (putting image and text data onto films or plates as part of the printing process), laser imaging and displays, switching in telecom fibres, instrumentation and research.

STG Series Free-space Acousto-optical Modulators

We offer a wide range of standard AO Modulators, for digital or analogue intensity modulation of laser beams. Their main specifications are as follows:

• Wavelength Range: 240nm to 2100nm

• Drive Frequencies: 20MHz to 350MHz

• Optical Rise-Times: Down to 5ns

• Modulation Bandwidths: Up to 100MHz

• Interaction Materials: Tellurium Dioxide, Lead Molybdate, Fused Silica, Crystal Quartz, Chalcogenide Glass, Flint Glass.

An RF Driver provides the electronic signal operating the AO Modulator. With a digital driver, an external TTL signal enables rapid on and off switching of the optical beam. Alternatively an anologue driver enables a variable intensity output, typically from 0% to 85% of the input beam. The maximum modulation bandwidth, or optical rise-time, is a function of the acoustic transit time across the optical beam. Therefore, for the highest speeds it is often necessary to focus the optical beam down to a small spot inside the modulator.

Our standard AOMs are listed below.

Our old AOM models are listed in the below table. These old models may or may not be in stock or obsolete and no longer produced. Please check with our sales regarding the availability of the below models.

Multi-channel Modulators

Acousto-optic multi-channel modulators (AOMC) allow multiple beams to be modulated or deflected independently by integrating an array of transducers with a single acousto-optic crystal. Our proprietary optical and electrical designs minimize crosstalk, allowing concurrent operation of up to 48 channels for modulation, and up to 8 channels for beam deflection. Our AOMCs are known for their reliable operation and high performance.

Multi-channel modulators have parallel beams as input, each beam independently controlled by a different transducer to modulate its intensity. Multi-channel modulators are most often used for high speed applications like micromachining and direct-write lithography, as each beam can be modulated independently.

These devices can also be used to increase throughput when writing large media by writing multiple beams at the same time. Our multi-channel modulators equal the performance available with our single channel modulators, and can be customized for large aperture applications as well as high speed, small aperture applications.

A multi-channel beam deflector however, generates multiple diffracted beams from a single input beam at specific locations by simultaneously applying multiple frequencies to a single transducer. Each inpidual channel is a deflector that can either scan the beam or produce multiple spots. This makes it possible to create a two-dimensional grid. For example, if a four channel beam deflector were configured so that each channel diffracted three spots, the result would be a 4x3 grid.

High laser damage threshold is achieved using low-scatter materials. These are inspected to rigorous quality standards. We grow our own tellurium dioxide and source high quality fused silica and crystalline quartz to ensure low insertion loss and excellent optical power handling.

Our standard models are below:

Details of STG Series Free-space Acousto-Optic Modulators (AOMs):

1. AO Modulator  M080-2G-LV1

• High efficiency (95% typical)

• Low drive power (0.3W typical)

• Compact

• Easy to align

The M080-2G-LV1 is a compact AO Modulator specifically designed for extra-cavity modulation of Nd:YAG/Nd:YVO4 lasers where fast modulation is not critical. Rise times down to 10μs are readily achievable, together with excellent efficiency, typically > 95% for a well-collimated laser beam. The relatively wide field of view means that good efficiency is achieved for more pergent beams.

• Interaction Material: TeO2

• Wavelength: 1064nm

• Anti-Reflection Coating: < 0.3% per surface

• Polarisation Alignment: ±5°

• Frequency: 80MHz

• Input Impedance: 50Ω

• Acoustic Mode: Slow Shear

• Active Aperture: 2.0 x 5.0mm

• Clear Aperture: 4.0 x 5.0mm (min)

• Recommended Beam Diameter: 1mm

• Input Polarisation: Linear - vertical to base

• Diffracted Beam Polarisation: Linear - rotated by 90° wrt input

• Diffraction Efficiency: > 90%

• RF Connector: SMA Female

• RF Power: 0.5W

• RF Driver Model No.: A36080, N21080-1DM or N21080-1AM

2. AO Modulator M111-10C-TR7

• 514 to 532 nm

• High damage threshold

• 111MHz drive frequency

An acousto-optic modulator ideal for use with frequency doubled DPSS lasers. Manufactured in Crystal Quartz for improved thermal management and efficiency, this modulator combines high quality optical finishing with in house anti-reflection coatings to provide high extinction ratio and optimised throughput. Alternative wavelengths, apertures or package designs are available.

• Interaction Material: Crystal Quartz

• Wavelength: 514 to 532nm

• Anti-Reflection Coating: < 0.3% per surface

• Transmission: > 99.5%

• Polarisation: Linear, vertical to base

• Extinction Ratio (1st order on / off) > 55dB

• Damage Threshold: > 50KW/cm2 (Average)

• > 500MW/cm2 (Peak)

• Frequency: 111MHz

• VSWR: < 1.2:1 (50Ω input impedance)

• Active Aperture: 2.0mm

• Diffraction Efficiency: > 85%

• Rise-Time / Fall-Time: 110ns / mm

• Separation Angle: 9.6mrad at 515nm

• RF Power: < 5.0W

• RF Driver Model No.: A35111, N31111-5DM, N31111-5AM

3. AO Modulator M080-2B/F-GH2

• 480 to 800nm

• 80MHz drive frequency

• Up to 2mm beam diameter

A general purpose acousto-optic modulator for use is in the visible or near infra-red spectral regions. It’s broadband anti-reflection coatings and large active aperture make it the ideal choice for cost-effective amplitude modulation of a wide range of low-power gas and diode lasers. Available for the visible (B/E) and near infra-red (F), with active apertures of 2mm, laser beams with diameters ranging from 0.5 to 2mm may be modulated at moderate speed with high efficiency. For faster modulation, please refer to our extensive range of other AO modulators.

• Interaction Material: Tellurium Dioxide

• Wavelength: 480 to 800nm

• Anti-Reflection Coating: < 0.5% per surface

• Transmission: > 95%

• Polarisation: Any

• Frequency: 80MHz

• VSWR: < 1.2:1 (50Ω input impedance)

• Active Aperture: 2mm

• Rise-Time / Fall-Time: 155ns/mm

• Diffracted Beam Ellipticity: < 5% typical

• Diffraction Efficiency: > 85% typical

• RF Power: < 2W

• Driver Selection: A36080,

• Digital Modulation: N21080-2DM

• Analogue Modulation: N21080-2AM

4. AO Modulator M250-2x-xx

• 488, 532 and 633nm

• 250MHz drive frequency

• 10ns rise-time

An acousto-optic modulator combining high efficiency and fast switching speed, is suitable for use with visible wavelength lasers. This AOM features excellent extinction ratio, superb diffraction efficiency even at maximum modulation rates and minimal optical beam quality distortion. Options include a choice of mounting and pivot holes, RF connectors and aperture dimensions. Alternative models in lead molybdate or for other wavelengths are available.

• Interaction Material: Tellurium Dioxide

• Acoustic Mode: Isotropic, compressional

• Wavelength M250-2B-P2: 488nm, < 20mW

• M250-2C-ES1: 532nm, < 20mW

• M250-2E-O2: 633nm

• Anti-Reflection Coating: < 0.2% per surface

• Transmission: > 97%

• Polarisation: Linear, vertical to base

• Frequency: 250MHz

• VSWR: < 1.2:1 (50Ω input impedance)

• Active Aperture: 0.4mm

• Separation Angle: 28 to 37mrad, wavelength dependant

• RF Power: < 1.5W

• Performance with a 65μm diameter, linearly polarised beam:

• Rise-Time / Fall-Time: 10ns

• Modulation Bandwidth: 50MHz

• Diffracted Beam Ellipticity: < 10%

• Diffraction Efficiency: > 85%

• Driver Selection: A36250, N21250-2AM, N21250-2DM

5. AO Modulator M350-2x

• 488nm, 532nm and 633nm

• 350MHz drive frequency

• 5ns rise-time

A high bandwidth acousto-optic modulator is for use in the visible RGB spectral region. Using specially selected top-grade tellurium dioxide and with our renowned quality manufacturing processes, this modulator provides fast switching capability at low RF drive powers. Available in three models, one each for red, green and blue, high efficiency coupled with excellent transmitted beam quality make it particularly suited to electronic pre-press applications.

• Interaction Material: Tellurium Dioxide

• Acoustic Mode: Isotropic, compressional

• Wavelength M350-2B: 488nm, < 20mW

• M350-2C: 532nm, < 20mW

• M350-2E: 633nm

• Anti-Reflection Coating: < 0.2% per surface

• Transmission: > 97%

• Polarisation: Linear, vertical to base

• Frequency: 350MHz

• VSWR: < 1.2:1 (50Ω input impedance)

• Active Aperture: 0.15mm

• Separation Angle: 40 to 52mrad, wavelength dependant

• RF Power: < 2W

• Performance with a 30μm diameter, linearly polarised beam:

• Rise-Time / Fall-Time: 5ns

• Modulation Bandwidth: 100MHz

• Diffracted Beam Ellipticity: < 15%

• Diffraction Efficiency: > 80%

• Driver Selection: Analogue / Digital Modulation: A35350

6.  AO Modulator M111-2J-AV1

• 1520 to 1630nm

• 111MHz drive frequency

• 60ns rise-time

A free-space acousto-optic modulator appropriate for use either intra-cavity or extacavity, for example to Q-Switch or modulate erbium doped fibre lasers. Broadband anti-reflection coatings, combined with top grade tellurium dioxide, guarantee excellent throughput and beam quality. Special design and high quality manufacturing processes result in superior efficiency with excellent extinction ratio.

• Interaction Material: Tellurium Dioxide

• Acoustic Mode: Isotropic, compressional

• Wavelength: 1520nm to 1630nm

• Transmission: > 97%

• Damage Threshold: >10MW/cm2 Pulsed, >50KW/cm2 CW

• Polarisation: Any

• Frequency: 111MHz

• VSWR: < 1·2:1 (50Ω Input Impedance)

• Active Aperture: 0.65mm

• Separation Angle: 39 to 43mrad, wavelength dependant

• RF Power: 3·5W

• Operating Temperature: +10 to +60ºC

• Storage Temperature: - 15 to +65ºC

• Performance with a 400μm diameter, linearly polarised beam:

• Rise-Time / Fall-Time: 61ns

• Modulation Bandwidth: 8.2MHz

• Extinction Ratio: > 40dB

• Diffracted Beam Ellipticity: < 20%

• Diffraction Efficiency: > 85%

• Driver Selection: A35111, N31111-3.5DM or N31111-3.5AM

7. AO Modulator M110-10UV-OR1

• 351, 355 & 364nm

• High damage threshold

• 110MHz drive frequency

An acousto-optic modulator ideal for use with 355nm frequency tripled Nd:YAG and Nd:YVO4 or 351nm / 364nm Argon lasers. Manufactured in Crystal Quartz for improved thermal management & efficiency. This modulator combines high quality optical finishing with in house anti-reflection coatings to provide high extinction ratio and optimised throughput. Alternative wavelengths, apertures or package designs are available. Please don’t hesitate to contact us with your specific requirements.

• Interaction Material: Crystal Quartz

• Wavelength: 351 to 364nm

• Anti-Reflection Coating: < 0.3% per surface at 355nm

• < 0.5% per surface at 351 to 364nm

• Transmission: > 99% at 355nm

• > 98.6% at 351 to 364nm

• Polarisation: Linear, vertical to base

• Extinction Ratio (1st order on / off) > 55dB

• Damage Threshold: > 50KW/cm2 (Average)

• > 500MW/cm2 (Peak)

• Frequency: 110MHz

• VSWR: < 1.2:1 (50Ω input impedance)

• Active Aperture: 3.0mm

• Diffraction Efficiency: > 85%

• Rise-Time / Fall-Time: 110ns / mm

• Separation Angle: 6.5mrad at 355nm

• RF Power: < 3.0W

• Driver Selection: A35111, N31111-3DM or N31111-3AM

8. AO Modulator M200-4A-GH11

• 380 to 430nm AO modulation

• 200MHz drive frequency

• 10ns rise-time

An acousto-optic modulator suitable for use with frequency doubled Ti:Sapphire lasers. Manufactured in fused silica and with our superior high damage threshold anti-reflection coatings this modulator provides extremely fast digital or analogue switching, coupled with an ultra-high extinction ratio and optimised throughput.

• Interaction Material: Fused Silica

• Acoustic Mode: Isotropic, compressional

• Wavelength: 380 to 430nm

• Polarisation: Linear, vertical to base

• Anti-Reflection Coating: < 0.5% per surface

• Transmission: > 98.5%

• Extinction Ratio (1st order on/off): > 55dB

• Frequency: 200MHz

• Active Aperture: 0.20mm

• Input Impedance: 50Ω

• Maximum RF Power Requirement: 2.5W

• Operating Temperature: +10 to +60°C

• Storage Temperature: -15 to +70°C

• Performance characteristics at 405nm:

• Beam Diameter: 90μm

• Rise-Time (10-90%): 10ns

• Modulation Bandwidth (3dB): 50MHz

• Diffracted Beam Ellipticity: < 15%

• Separation Angle: 13.5mrad

• Diffraction Efficiency: > 80%

• RF Power: 2W

• Driver Selection: A35200, N21200-2AM or N21200-2DM

9. AO Modulator M200-4B/E-LD5

• High intensity RGB modulation

• 200MHz drive frequency

• 10ns rise-time

An acousto-optic modulator for use with high intensity RGB lasers, ideally suited for laser display and reprographic applications. Manufactured in fused silica and with our superior high damage threshold anti-reflection coatings this modulator provides extremely fast digital or analogue switching in the RGB range, coupled with an ultra-high extinction ratio and optimised throughput.

• Device: AO Modulator

• Interaction Medium: Fused Silica

• Acoustic Mode: Isotropic, compressional

• Operational Wavelength: RGB (446nm, 532nm, 628nm)

• Polarisation: Linear, vertical to base

• Laser Power Maximum: > 100W

• Optical Faces: 1deg wedged

• AR coating reflectivity: ≤ 0·5% per surface

• Transmission: > 97%

• Extinction Ratio (1st order on/off) : > 55dB

• RF Drive Frequency: 200MHz

• Active Aperture: 0.2mm

• Diffraction Efficiency: > 70% (typically 75%) at 75um beam diameter

• Rise-Time: 10ns at 532nm, 90um beam diameter

• Input Impedance: 50Ω

• Maximum RF Drive Power: 6W

• Operating Temperature: +10 to +60°C

• Storage Temperature: -15 to +70°C

• Wavelength:          446nm / 532nm / 628nm

• Beam Diameter:      90μm / 90μm /120μm

• Rise-Time (10-90%):   10ns /10ns /13.5ns

• Modulation Bandwidth (3dB): 50MHz/ 50MHz /37MHz

• Diffracted Beam Ellipticity:  16%  / 21% /17%

• Separation Angle:   15mrad /18mrad / 21mrad

• Diffraction Efficiency:    > 80% /  > 80% / > 80%

• RF Power:        3W / 4W/5.5W

• Driver Selection: N31200-6DM, N31200-6AM

10. M080-2B/F-GH2

11. I-M150-0.4C2G-GH42

12. AOMO 3350-111

• **The maximum optical power density should not exceed 1KW/cm^2 CW/ave for wavelengths <550nm.  The optical power density should not exceed 100KW/cm^2 ave/CW for longer wavelengths.

13. AOMO 3350-120

14. Free Space AOMs

2. Multi-channel Modulators

Acousto-optic multi-channel modulators (AOMC) allow multiple beams to be modulated or deflected independently by integrating an array of transducers with a single acousto-optic crystal. Our proprietary optical and electrical designs minimize crosstalk, allowing concurrent operation of up to 48 channels for modulation, and up to 8 channels for beam deflection. Our AOMCs are known for their reliable operation and high performance.

Multi-channel modulators have parallel beams as input, each beam independently controlled by a different transducer to modulate its intensity. Multi-channel modulators are most often used for high speed applications like micromachining and direct-write lithography, as each beam can be modulated independently.

These devices can also be used to increase throughput when writing large media by writing multiple beams at the same time. Our multi-channel modulators equal the performance available with our single channel modulators, and can be customized for large aperture applications as well as high speed, small aperture applications.

A multi-channel beam deflector however, generates multiple diffracted beams from a single input beam at specific locations by simultaneously applying multiple frequencies to a single transducer. Each inpidual channel is a deflector that can either scan the beam or produce multiple spots. This makes it possible to create a two dimensional grid. For example, if a four channel beam deflector were configured so that each channel diffracted three spots, the result would be a 4x3 grid.

High laser damage threshold is achieved using low-scatter materials. These are inspected to rigorous quality standards. We grow our own tellurium dioxide and source high quality fused silica and crystalline quartz to ensure low insertion loss and excellent optical power handling.

Our standard model are listed below:

We have more AOMs and please contact us for more detailed data sheets. Customer-designed and -made AOMs are also available. Please call us for more information.