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The acousto-optical Q-switch often used in the laser marking makes use of mutual interaction between an ultrasonic wave and a light beam in a scattering medium. The light beam that enters in a direction forming a Bragg angle to the wave surface of the acoustic wave in the scattering medium is diffracted in accordance with periodic changes in the diffraction rate produced by the acoustic wave.

 

The situation is briefly explained. First of all, an RF signal is impressed to the transducer adhered to the molten quartz and thickness extensional vibration is produced. Ultrasonic shear waves are caused to advance in the molten quartz by this vibration, and phase grating formed by acoustic waves is produced. The laser beam is diffracted when it satisfies the Bragg angle with respect to this phase grating, and is separated in space from the incident light.

 

If the laser optical resonator is constructed against 0-dimensional diffracted light (undiffracted light), the diffracted light deviates from the laser optical resonator axis when a RF signal is impressed. As a result, loss occurs in the laser optical resonator and laser oscillation is suppressed. To make use of this phenomenon, an RF signal is impressed for a certain length of time only (status of low Q-value) to suspend laser oscillation. In the meantime, the population inversion of the Nd:YAG rod is accumulated by continuous pumping. When the RF signal is reduced to zero (status of high Q-value) and the loss to the laser optical resonator is removed, the accumulated energy is activated as laser oscillation in a pulse form within an extremely short length of time. They are Q-switch pulses.

 

This situation is briefly explained. When an RF signal is subjected to pulse modulation, it is possible to periodically take out a Q-switch pulse. When the period of Q-switch pulses becomes shorter than the life (about 200 ms) of the higher order of the Nd:YAG rod, however, the population inversion decreases and the peak value of Q-switch pulses decreases.

 

1. QS Series Q-switches at 1064nm

  

A water-cooled acousto-optic Q-Switch for use in high-power Nd:YAG laser systems. Combining top grade fused silica with high quality optical finishing and in-house anti-reflection coatings, this Q-Switch exhibits very low insertion loss and high damage threshold. Through an innovative design and manufacturing process, RF powers up to 100W may be applied.

Standard options include a choice of frequencies (24 to 68MHz), active apertures (1 to 8mm), acoustic modes (compressional for linear polarisation, shear for unpolarised) and water connectors. Customised housings are available for OEM’s.

   

Specifications:

  • Model No: See "Options" below

  • Interaction Medium: Fused Silica

  • Operational Wavelength: 1064nm

  • Anti Reflection Coating: Hard multi-layer dielectric

  • - Reflectivity: <0·2% / surface (< 0·1% typical)

  • - Damage Threshold: > 500MW cm-2

  • Insertion Loss: <10% (< 5% typical)

  • Active Aperture: See "Options" below

  • VSWR: 1·2:1

  • Maximum CW Drive Power: 100W

  • Thermal Interlock: +50ºC

qswitch2.jpg (52831 字节)

Water Cooling

  • Recommended water operating: <32ºC

  • Recommended water maximum: 40ºC

  • Water Connectors: See "Options" below

 

Options

QS

27

-4

S

-B

-X X n

DEVICE

FREQUENCY

ACTIVE
APERTURE

ACOUSTIC
MODE

WATER
CONNECTOR

SPECIAL
DESIGNATION

  • Device : QS - Q-Switch

  • Frequency : 24, 27, 41 - Value in MHz

  • Aperture : 1.6, 2, 3, 4, 5, 6·5, 8 - Value in mm (In general, the aperture of Q-switch is equal to or larger than the diameter of laser beam or YAG rod.

  • Acoustic Mode : C - Compressional, S - Shear

  • Water Connector : S - Screw-on (Swagelok etc.), B - Barbed Push-on

  • Special Designation : - For non-standard Q-switch models identification characters which define the configuration may be allocated.

Driver Selection                                                                                               Acousto-Optic Q-Switch Selection Guide

QSD series or R3900 series drivers

 

2. QS Series Q-switches at 1319-1342nm

 

Model No.

 QS027-4H-xxx

qswitch2.jpg (52831 字节)

Interaction material

 Infrasil (water-free fused silica)

Wavelength

 1319-1342nm

AR coating reflectivity

 < 0.2% per surface

Damage threshold

 > 100MWcm-2

Polarisation

 Linear (vertical to base)

Interaction length

 46.0mm

RF frequency

 27.12MHz

VSWR

 < 1.2 1 at 50.

Acoustic Mode

 Compressional

Active aperture

 5.0mm

Loss modulation

 > 80% at 50W RF power

Housing

 Standard QS24/27 range (Aluminium)

Water connectors

 Barbed

 

3. QS Series Super Q-switches at 1064nm

 

Model: QS2x-xD-x-xxx

  • High efficiency

  • For unpolarised, high power, high gain lasers

  • 2 x 50W RF power handling

A new compressional mode, water-cooled, AO Q-Switch designed for use in high power unpolarised lasers giving faster switching, better pulse-to-pulse stability and higher power densities. Enhance your systems performance with greater punch and increased power, specifically for laser processing applications.

Before the Super Q-Switch, some customers were using 2 x Compressional mode Q-Switches (like the QS27-4C-S) in the same cavity. One of the Q-Switches is rotated 90degrees to the other. Because the Compressional mode Q-Switch is more efficient for polarised light, the first Q-Switch would block one polarisation & the second Q-Switch blocks the other. This is a good solution, but takes a large space in the cavity. The Super Q-Switch gives the same performance as using 2 x Compressional Q-Switch, but they are incorporated into 1 device.  

This Q-switch uses a dual channel driver to operate two orthogonal compressional mode transducers bonded to a single monolithic optical cell and mounted in one convenient housing. Our proprietary bonding techniques and power handling technology allows this device to operate up to 50W per channel giving an efficient, compact, single device for the next generation of high power, high gain, solid state lasers.

 

Interaction Material

 Fused Silica

qswitchsuper2.jpg (14295 字节)

 

 

  

 

 

 

qswitchsuper.jpg (75942 字节)

Wavelength

 1047 to 1064nm

Anti-Reflection Coating

 < 0.2% per surface

Damage Threshold

 > 500MWcm-2 (1GWcm-2 typical)

Transmission (single pass)

 > 99.6%

Frequency

 24.00 or 27.12MHz

VSWR

 < 1.2:1 (50. input impedance)

Active Aperture

 1.6, 2, 3, 4, 5 or 6.5mm2

Clear Aperture

 9 x 9mm

Acoustic Mode

 Compressional (Orthogonal)

Rise-Time / Fall-Time

 109ns/mm

RF Power Rating

 2 x 50W cw

Water Flow Rate

 190cc / minute, minimum

Maximum Water Temperature

 +40°C (recommended, 22°C to 32°C)

Water Connectors

 Screw-fit or Barbed (push-on)

Thermal Switch Cut-Off

 +55°C ± 5°C

Housing / Flow Chamber Material

 Aluminium HE30TF

 

Driver Selection

  •  Aperture size 1.6D, 2D or 3D, use 25W dual channel driver  (R390xx25DMzz-2CH, or R390xx-25DSzzz-2CH)

  • Aperture size 4D, 5D or 6.5D, use 50W dual channel driver  (R390xx25DMzz-2CH, or R390xx-25DSzzz-2CH)

Options and Model

 

4. Stallion Series AO Q-Switches at 1064nm Wavelength

 

A ‘Stallion’ version of our industry standard water cooled Acousto-optic Q-Switch, for use in high power lamp or diode pumped Nd:YAG lasers.

 

The patent pending ‘Stallion’ manufacturing technique provides superior corrosion resistance whilst maintaining optimum performance and RF power handling capabilities up to 100W.

 

Combining top grade fused silica with high quality optical finishing and in-house anti-reflection coatings, this Q-Switch exhibits very low insertion loss and high damage threshold.

 

In addition to the standard product shown, custom configurations are available for specialized applications. These include alternative housing options, wavelengths and RF frequencies.

 

Key Features:

  • Industry standard for Nd:YAG lasers

  • Superior corrosion resistance

  • Stainless steel cooling channels

  • High damage threshold

  • Push fit water-connectors

  • Up to 100W RF power handling

  • Custom configurations available

Applications:

  • Material processing:

  • Laser marking

  • Laser engraving

  • Laser cutting

  • Laser drilling

  • Medical (surgery)

  • Lithography

Technical Specifications:

 
   

Interaction material:

 Fused silicon

Wavelength:

 1064nm

AR coating reflectivity:

 < 0.2% per surface

Damage threshold:

 > 1GWcm-2

Transmission (single pass):

 > 99.6%

Static insertion loss:

 ≤ 6% at 50W laser power

VSWR:

 < 1.2:1 (<1.4:1 at 50W RF power)

RF power rating:

 100W cw (max)

Water flow rate:

 > 190cc / minute

Water-cooling channel material:

 Stainless steel 316

Recommended water temperature:

 +22oC to +32oC

Thermal switch cut-off:

 +55oC +/- 5oC

 

Ordering Codes

Example: I-QS027-4S4G-N5-ST1 (Q-Switch, 27.12MHz, 4mm active aperture, shear mode, fused silica, 1064nm, 4mm OD straight push fit water-connectors, BNC, Stallion housing with M3 mounting holes).

 

 

5. Other Q-Switches

 

The Q-Switches are for use in both industrial and laboratory applications. Q-Switching is used principally on high peak power solid state Nd:YAG lasers at 1.06 micrometer wavelength. The Q-Switches are divided into three categories: for use with multi-mode, un-polarized lasers, with beam sizes 5mm and larger; for use with miniature, polarized or un-polarized, solid state diode pumped lasers; and single mode, polarized, low divergence solid state lasers, with beam size of 1 to 2 mm.

 

Wavelength(nm)

 

Q-Switch Model

Driver Power

Loss
Modulation (%@Watts) @1064nm

Polarization

Active Aperture

 (mm)

Center Frequency

 (MHz)

Rise Time

(ns / mm beam dia.)

Optical Power Density /(cm2)

Ave./Pk

Interaction Material

Outlook
drawing

10.6um

37027-3

30

85

3

27.12

120

500

Ge

53B2220

10.6um

37027-5

30

75

5

27.12

120

500

Ge

53B2220

1064

32024-50-4

50

55

4x13

24

175

50K/500M

Fused Silica

53B0290

1064

32027-50-4

50

55

4x13

27.12

175

50K/500M

Fused Silica

53B0290

1064

33024-50-5-I-HGM-W

50

70

5x10

24

115

50K/500M

Crystal Quartz

53B1059

1064

33024-50-5-I-HGM-CMS

50

70

5x10

24

115

50K/500M

Crystal Quartz

53B1186

1064

33027-50-5-I-HGM-W

50

85

70

5x10

27.12

115

50W/500M

Crystal Quartz

53B1059

1064

33027-50-5-I-HGM

50

70

5x10

27.12

115

50W/500M

Crystal Quartz

53B1290

1064

33027-50-5-I-HGM-CMS

50

70

5x10

27.12

115

50W/500M

Crystal Quartz

53B1186

1064

33027-50-5-I-M3

50

85

70

5x10

27.12

115

 

Crystal Quartz

53C1244

1064

32024-70-7

70

55

7x13

24

175

50K500M

Fused Silica

53B0290

1064

32027-70-7

70

55

7x13

27.12

175

50K/500M

Fused Silica

53B0290

1064

33024-70-7-I-HGM-W

70

85

7x10

24

115

50K/500M

Crystal Quartz

53B1059

1064

33024-70-7-I-HGM-CMS

70

85

7x10

24

115

50K/500M

Crystal Quartz

53B1186

1064

33027-70-7-I-HGM-W

70

85

7x10

27.12

115

50K/500M

Crystal Quartz

53B1059

1064

33027-70-7-I-HGM-CMS

70

85

7x10

27.12

115

50K/500M

Crystal Quartz

53B1186

1064

32024-100-4-HGM-W

100

90

4x13

24

175

50K/500M

Fused Silica

53B0290

1064

32027-100-4-HGM-W

100

90

4x13

27.12

175

50K/500M

Fused Silica

53B1059

1064

32027-100-4-HGM-CMS

100

90

4x13

27.12

175

50K/500M

Fused Silica

53B1186

 

Remark: EO Q-switches operating at 10.6um (CO2 lasers) available.

 

6. STBR series free space Q-switch

STBR series Acousto-Optic Q-switching systems for industrial and laboratory applications. The STBR free space Q-switches are designed for the highest conversion efficiency of RF energy into acoustic energy by attaching the transducer to the crystal with an advanced vacuum metallized process. Q-switches are special modulators designed for use inside laser cavities. They are fabricated from high optical quality Fused Quartz, Flint Glass, and Tellurium Dioxide, or other acousto-optic materials with Brewster cut optical faces or durable hard oxide AR coatings for high optical power applications.

Model # FSQ-24-2-BC FSQ-27-5-BC FSQ-80-5-BC TEQ-27-4-BC TEQ-80-20-BC
Substrate SiO2 SiO2 SiO2 TeO2 TeO2
Brewster cut yes yes ye yes yes
Laser Wavelength (nm) 1064 1064 1060 2940 800
Active Aperture (mm) 2 2 1 1.5 3
Center Frequency (MHz) 2 27 80 27 80
Digital Modulation Bandwidth (MHz) 2 5 6.5 4 (3dB Bandwidth) 20 (3dB Bandwidth)
Optical Transmission (%) 99.8 99.8 >99.5 >99.5 >99.5
Maximum Diffraction Efficiency (%) 30 30 25 >50 >65
Rise Time (nsec) 100 100 85 150/630
 
80/400
Acoustic Velocity (m/s) 5.96E+3 5.96E+3 5.96E+3 4.2E+3 4.2E+3

Wave Front Distortion

λ/10

λ/10

λ/10

λ/10

λ/10

Separation Angle

5 mrad @ 1064nm

5 mrad @ 1064nm

5 mrad @ 1064nm

1 deg @ 2940nm

0.9 deg @ 800nm

Input Impedance

50 ohms

50 ohms

50 ohms

50 ohms

50 ohms

Optical Polarization

Linear (perpendicular to acoustic wave)

Linear

Perpendicular to acoustic wave

VSWR

2.1:1

For the associated RF drivers, please refer to “RF Drivers for STBR series”

 

Air-cooled Q-switch        Q-switch drivers        Fiber Q

Basics of Acousto-Optic Q-switch                     Frequently Asked Questions

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10 Bukit Batok Crescent #07-02 The Spire Singapore 658079

Tel: +65 63167112 Fax: +65 63167113  

E-mail: sales@sintec.sg sales@SintecOptronics.com

URL: http://www.sintec.sghttp://www.SintecOptronics.com

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