Water-cooled AO Q-switch

  • Update:Mar 20, 2017
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We provide full range of acousto-optic Q-switches such as water- and air-cooled Q-switches at the RF frequency of 27MHz 41MHz and 80MHz etc in industrial standard.

Product Introduction

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.


Water Cooling


QS 27 -4 S -B -X X n
Q-Switch 24, 27, 41 (MHz) 1.6, 2, 3, 5, 6.5, 8(mm) C- Compressional S- Shear S- Screw-on B- Barbed Push-on  

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

Model No. QS027-4H-xxx
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 (QS2x-xD-x-xxx)

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.

Technical Specifications:

Interaction Material Fused Silica
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:

QS 2x -x D -x -xxx
  24 or 27 (MHz) 1.6, 2, 3, 4, 5 or 6.5 (mm) Orthogonal B - Barbed S - Screw-fit  

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:


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-QS027-1.6C4-N5-STI)

I-QS xxx -xxx x4 -x5 -STI
Q-Switch 024, 027, 041, 068 (MHz) 1.6, 2, 3, 5, 6.5, 8 (mm) C- Compressional S- Shear N- 4mmOD straight push fit P- 6mmOD straight push fit Q- 4mmOD right angle push fit U- 6mmOD right angle push fit  

5. STBR Free Sapce Q-Switches

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