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AO Q-Switch

CASTECH's AO Q-Switch is industrial grade product and it can meet the different needs of the customer. It has many advantages, such as compact, high damage threshold and high efficiency. It is widely used in material processing and scientific. In addition, it also can be customized to the parameters according to customer demand.


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    When placed inside a laser cavity, an acousto-optic Q-switch (AOQS) can be used to control the amount of light circulating within the resonator via the acousto-optic effect. CASTECH's AO Q-Switch is industrial grade product and it can meet the different needs of the customer. It has many advantages, such as compact, high damage threshold and high efficiency. It is widely used in material processing and scientific. In addition, it also can be customized to the parameters according to customer demand.

 

Features:                                      Applications:

◆ Compact package                                             ◆ Material processing

◆ Conduction-cooled                                            ◆ Medical

◆ High damage threshold                                     ◆ Scientific

◆ High efficiency

 

Specifications:

Product code

CAQS-027-ah-FSt-w-c

CAQS-041-ah-CQC-w-c

CAQS-068-ah-CQC-w-c

CAQS-080-ah-CQC-w-c

Material

Fused silica

Crystal Quartz

Crystal Quartz

Crystal Quartz

Wavelength

1064,… nm

355,1030,1064,… nm

355,1030,1064,… nm

355,1030,1064,… nm

Transmission(Single pass)

≥99.6%

≥99.6%

≥99.6%

≥99.6%

Damage threshold

1GW/cm²

1GW/cm²

1GW/cm²

1GW/cm²

AR coating reflection

0.2% per surface

0.2% per surface

0.2% per surface

0.2% per surface

Polarization

Random

Linearvertical to base

Linearvertical to base

Linearvertical to base

Aperture

1.6,2,3,4.5,6,…mm

0.8,1,1.5,1.8,2,3,…mm

0.8,1,1.5,1.8,2,3,…mm

0.5,1,1.5,2,… mm

Acoustic mode

Compressional

Compressional

Compressional

Compressional

RF Frequency

27 MHz

40.68 MHz

68 MHz

80MHz

RF power rating(Maximum)

50 W

20 W

25 W

15 W

RF connector

BNC

SMA,BNC,MMCX,…

SMA,BNC,MMCX,…

SMA,BNC,MMCX,…

Rise time10~90%

/

113 ns/mm

113 ns/mm

113 ns/mm

Loss Modulator

60%

≥85%

≥85%

≥85%

Diffraction angle

3.32 mrad

7.5mrad

12.6 mrad

14.9mrad

VSWR

1.2:1

1.2:1

1.2:1

1.2:1

Cooling

Water-cooled

Conduction-cooled

Conduction-cooled

Conduction-cooled

Storage temperature

0℃~50℃

-20℃~70℃

-20℃~70℃

-20℃~70℃

Product specifications are subject to change without notice;

Customized (Wavelength, Dimension, Power Handling , etc) are available;

Note:All products are RoHS compliant.

 

  

 

Dimensions (mm):

A01:                     

 

A02:

 

A08:

1.Glossary

Bragg cell: A device using a bulk acousto-optic interaction (eg. deflectors, modulators, etc...).

 

“Zero” order,”1st” order: The zero order is the beam directly transmitted through the cell. The first order is the diffracted beam generated when the laser beam interacts with the acoustic wave.

 

Bragg angle (QB): The particular angle of incidence (between the incident beam and the acoustic wave) which gives efficient diffraction into a single diffracted order. This angle will depend on the wavelength and the RF frequency.

 

Separation angle (Q): The angle between the zero order and the first order.

 

RF Bandwidth (DF): For a given orientation and optical wavelength there is a particular RF frequency which matches the Bragg criteria. However, there will be a range of frequencies for which the situation is still close enough to optimum for diffraction still to be efficient. This RF bandwidth determines, for instance, the scan angle of a deflector or the tuning range of an AOTF.

 

Maximum deflection angle (DQ): The angle through which the first order beam will scan when the RF frequency is varied across the full RF bandwidth.

 

Rise time (TR): Proportional to the time the acoustic wave takes to cross the laser beam and, therefore, the time it takes the beam to respond to a change in the RF signal. The rise time can be reduced by reducing the beam’s width.

  

Modulation bandwidth (DFmod): The maximum frequency at which the light beam can be amplitude modulated. It is related to the rise time - and can be increased by reducing the diameter of the laser beam.

 

Efficiency (h): The fraction of the zero order beam which can be diffracted into the “1st” order beam.

 

Extinction ratio (ER): The ratio between maximum and minimum light intensity in the “1st” order beam, when the acoustic wave is “on” and “off” respectively.

 

Frequency shift (F): The difference in frequency between the diffracted and incident light beams. This shift is equal to the acoustic frequency and can be a shift up or down depending on orientation.

 

Resolution (N): The number of resolvable points, which a deflector can generate - corresponding to the maximum number of separate positions of the diffracted light beam - as defined by the Rayleigh criterion.

 

RF Power (PRF): The electrical power delivered by the driver.

 

Acoustic power (Pa ): The acoustic power generated in the crystal by the piezoelectric transducer. This will be lower than the RF power as the electro-mechanical conversion ratio is lower than 1.

 

2.Physical Principles

    An RF signal applied to a piezo-electric transducer, bonded to a suitable crystal, will generate an acoustic wave. This acts like a “phase grating”, traveling through the crystal at the acoustic velocity of the material and with an acoustic wave-length dependent on the frequency of the RF signal. Any incident laser beam will be diffracted by this grating, generally giving a number of diffracted beams.

 

3.Acousto-Optic Q-Switches

    When placed inside a laser cavity, an acousto-optic Q-switch (AOQS) can be used to control the amount of light circulating within the resonator via the acousto-optic effect. When turned on, an AOQS diffracts light out of the optical beam path within the cavity, thus increasing losses and reducing the Q-factor. While loss in the cavity is high and pumping continues, lasing cannot occur, but a population inversion can build up within the gain medium. Once the gain is saturated, the RF power to the acousto-optic Q-switch is turned off, reducing loss within the cavity very quickly. This increases the Q-factor and allows rapid amplification to create a very high intensity, short pulse.

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