Electro-Optic Q-switch (Pockel cell)

Electro-Optic Q-switch (Pockel cell)

APockels cell alters the polarization state of light passing through it when an applied voltage induces birefringence changes in an electro-optic crystal such as KD*P and BBO. When used in conjunction with polarizers, these cells can function as optic

A Pockels cell alters the polarization state of light passing through it when an applied voltage induces birefringence changes in an electro-optic crystal such as KD*P and BBO. When used in conjunction with polarizers, these cells can function as optical switches, or laser Q-switches. Frequently, Q-switches are employed in laser cavities for the purpose of shortening the output pulse, resulting in a light beam with enhanced peak intensity. In order to provide the device best suited to your purpose, we offer the industry standard QX series, economical IMPACT cells, BBO-based LightGate, and large-aperture TX Pockels cell lines. High-speed electronic drivers properly matched to the cell produce the best results for short pulse applications.

The Electro-Optic Effect

The linear electro-optic effect, also known as the Pockels effect, describes the variation of the refractive index of an optical medium under the influence of an external electrical field. In this case certain crystals become birefringent in the direction of the optical axis which is isotropic without an applied voltage.

When linearly polarized light propagates along the direction of the optical axis of the crystal, its state of polarization remains unchanged as long as no voltage is applied. When a voltage is applied, the light exits the crystal in a state of polarization which is in general elliptical.

In this way phase plates can be realized in analogy to conventional polarization optics. Phase plates introduce a phase shift between the ordinary and the extraordinary beam. Unlike conventional optics, the magnitude of the phase shift can be adjusted with an externally applied voltage and a λ/4 or λ/2 retardation can be achieved at a given wavelength. This presupposes that the plane of polarization of the incident light bisects the right angle between the axes which have been electrically induced. In the longitudinal Pockels effect the direction of the light beam is parallel to the direction of the electric field. In the transverse Pockels cell they are perpendicular to each other. The most common application of the Pockels cell is the switching of the quality factor of a laser cavity.


Laser activity begins when the threshold condition is met: the optical amplification for one round trip in the laser resonator is greater than the losses (output coupling, diffraction, absorption, scattering). The laser continues emitting until either the stored energy is exhausted, or the input from the pump source stops. Only a fraction of the storage capacity is effectively used in the operating mode. If it were possible to block the laser action long enough to store a maximum energy, then this energy could be released in a very short time period.

A method to accomplish this is called Q-switching. The resonator quality, which represents a measure of the losses in the resonator, is kept low until the maximum energy is stored. A rapid increase of the resonator quality then takes the laser high above threshold, and the stored energy can be released in a very short time. The resonator quality can be controlled as a function of time in a number of ways. In particular, deep modulation of the resonator quality is possible with components that influence the state of polarization of the light. Rotating the polarization plane of linearly polarized light by 90°, the light can be guided out of the laser at a polarizer. The modulation depth, apart from the homogeneity of the 90° rotation, is only determined by the degree of extinction of the polarizer.

The linear electro-optical (Pockels) effect plays a predominant role besides the linear magneto-optical (Faraday) and the quadratic electro-optical (Kerr) effect. Typical electro-optic Q-switches operate in a so called λ/4 mode.

a) Off Q-Switching

Light emitted by the laser rod (1) is linearly polarized by the polarizer (2). If a λ/4 voltage is applied to the Pockels cell (3), then on exit, the light is circularly polarized. After reflection from the resonator mirror (4) and a further passage through the Pockels cell, the light is once again polarized, but the plane of polarization has been rotated by 90°. The light is deflected out of the resonator at the polarizer, but the resonator quality is low and the laser does not start to oscillate. At the moment the maximum storage capacity of the active medium has been reached, the voltage of the Pockels cell is turned off very rapidly; the resonator quality increases immediately and a very short laser pulse is emitted. The use of a polarizer can be omitted for active materials which show polarization dependent amplification (eg. Nd:YalO3, Alexandrite, Ruby, etc.).

b) On Q-Switching

Unlike off Q-switching, a λ/4 plate (6) is used between the Pockels cell (3) and the resonator mirror (4). If no voltage is applied to the Pockels cell the laser resonator is blocked: no laser action takes place. A voltage pulse opens the resonator and permits the emission of laser light.

Pulse Picking

Typically Femto-Second-Lasers emit pulses with a repetition rate of several 10MHz. However many applications like regenerative amplifying require slower repetition rates. Here a Pockels cell can be used as an optical switch: by applying ultra fast and precisely timed λ/2-voltage pulses on the Pockels cell, the polarization of the Laser light can be controlled pulse wise. Thus, combined with a polarizer the Pockels cell works as an optical gate.

Selection Criteria

The selection of the correct Q-switch for a given application is determined by the excitation of the laser; the required pulse parameters, the switching voltage, the switching speed of the Pockels cell, the wavelength, polarization state and degree of coherence of the light.

Type of Excitation

Basically, both off and on Q-switching are equivalent in physical terms for both cw and for pulse pumped lasers. On Q-switching is, however, recommended in cw operation because a high voltage pulse and not a rapid high voltage switch-off is necessary to generate a laser pulse. This method also extends the life time of the cell. Over a long period of time, the continuous application of a high voltage would lead to electrochemical degradation effects in the KD*P crystal. We advice the use of an on Q-switching driver. Off Q-switching is more advantageous for lasers stimulated with flash lamps because the λ/4 plate is not required. In order to prevent the electrochemical degradation of the KD*P crystal in the off Q-switching mode we recommend a trigger scheme in which the high voltage is turned off between the flashlamp pulses and turned on to close the laser cavity before the onset of the pump pulse. The cell CPC and SPC series are recommended for diode pumped solid state lasers. These cells are ultra compact and will operate in a short length resonator: this is necessary to achieve very short laser pulses.

Pulse Parameters

The series LM n, LM n IM, and LM n SG cells are recommended for lasers with a power density of up to 500MW/cm². The LM n and LM n SG cells are used for lasers with very high amplification. The SG cells with sol-gel technology have the same transmission as the immersion cells and both are typically used when a higher transmission is required. At high pulse energies LMx cells are preferred.

Brewster Pockels cells are recommended for lasers with low amplification, such as Alexandrite lasers. The passive resonator losses are minimal due to a high transmission of 99%.

The CPC and SPC series cells are suitable for small, compact lasers and especially for OEM applications. They are available as dry cells and immersion cells.

The level of deuterium content in an electro-optic crystal influences the spectral position of the infrared edge. The higher the deuterium level the further the absorption edge is shifted into the infrared spectral region: for Nd:YAG at 1064nm, the laser absorption decreases. Crystals, which are deuterated to >98%, are available for lasers with a high repetition rate or a high average output power.

Pockels Cell Switching Voltage

Using double Pockels cells can half the switching voltage. This is achieved by switching two crystals electrically in parallel and optically in series. The damage threshold is very high and the cells are mainly used outside the resonator.

Electro Optic Material

The selection of the electro-optic material depends on its transmission range. Further on the Laser parameters and the application as well have to be taken into account.

For wavelengths from 0.25μm to 1.1μm, longitudinal Pockels cells made of KD*P and a deuterium content of 95% should be considered. If the deuterium content is higher the absorption edge of the material is shifted further into the infrared. KD*P crystal cells with a deuterium content >98% can be used up to 1.3μm.

KD*P can be grown with high optical uniformity and is therefore recommended for large apertures. The spectral window of BBO also ranges from 0.25μm to 1.3μm, but besides BBO also provides a low dielectric constant and a high damage threshold. Therefore BBO is recommended for Lasers with high repetition rate and high average powers. RTP, with an optical bandwidth from 0.5μm up to 1.5μm combines low switching voltage and high laser induced damage threshold. Together with its relative insensitivity for Piezo effects RTP is best suited for precise switching in high repetition rate lasers with super fast voltage drivers.

For wavelengths from 1.5μm up to 3μm we recommend LiNbO3.

Suppression of Piezo Effects

Like any other insulating material electro optical crystals show Piezo effects when high voltage is applied. The extend of the Piezo ringing depends on the electro optic material and usually its effect on the extinction ratio is negligible when used for Q-switching. However for pulse picking applications, which require highly precise switching behaviour, we offer specially Piezo damped Pockels cells which suppress these ringing effects efficiently.

State of Polarization

The MIQS and CIQS series cells are supplied with an integrated polarizer: the alignment of the Pockels cell relative to the polarizer thus becomes unnecessary. The rotational position of the cell relative to the resonator axis can be chosen at will. However, should the polarization state of the light in the resonator be determined by other components, such as anisotropic amplification of the laser crystal or Brewster surfaces of the laser rod, then the rotational position of the cell will be determined by these factors. Thin film polarizers are used and the substrate is mounted at the Brewster angle. A parallel beam displacement of 1mm results from this configuration and can be compensated by adjusting the resonator.

In order to provide the device best suited to your purpose, we offer the industry standard QX series, economical IMPACT cells, BBO-based LightGate, and large-aperture TX Pockels cell lines. High-speed electronic drivers properly matched to the cell produce the best results for short pulse applications.

You can operate the cell with either a pull-up voltage or a pull-down voltage. Changing the polarity will only change the direction of the phase rotation. You should not, however, operate the cell with a constant applied voltage potential between the terminals, or a duty cycle greater than ~ 2%.

STG Series Pockels Cell (EO Q-switch, Electro-optic Q-switch)

A Pockels cell alters the polarization state of light passing through it when an applied voltage induces birefringence changes in an electro-optic crystal such as KD*P and BBO. When used in conjunction with polarizers, these cells can function as optical switches, or laser Q-switches. Frequently, Q-switches are employed in laser cavities for the purpose of shortening the output pulse, resulting in a light beam with enhanced peak intensity. In order to provide the device best suited to your purpose, we offer the industry standard ST-QX series, economical STG-IMPACT cells, BBO-based STG-LightGate, and large-aperture STG-TX Pockels cell lines. High-speed electronic drivers properly matched to the cell produce the best results for short pulse applications.

You can operate the cell with either a pull-up voltage or a pull-down voltage. Changing the polarity will only change the direction of the phase rotation. You should not, however, operate the cell with a constant applied voltage potential between the terminals, or a duty cycle greater than ~ 2%.

List of STG Series Pockels Cells

Product Series Wavelength Voltage Contrast Ratio Active Aperture Optical Material
STG-Chiron BBO 0.2 1.65µm > 500 1 at @ 1064 nm 3.25 mm BBO
CdTe STG-IRX Mid-IR 5-12 µm >500 1 @ 10.6 µm 3 - 7,4 x10 mm CdTe
STG-IMPACT 300-1100 nm >2000 1 @ 1064 nm 8 - 13 mm KD*P
STG-QX1014A Short Path Length 300-1100 nm >450 1 N/A KD*P
STG-QX Series 300-1200 nm varies 9.25 - 19.5 mm KD*P
STG-TX Series 300-1300 nm varies 19.5 - 99 mm KD*P
STG-LightGate Series BBO 300- 600 nm >1000 1 @ 1064 nm 2.6 - 7 mm BBO

1. STG-IMPACT Series EO Q-switches

From the world leader in nonlinear materials and electro-optic devices comes the ideal Pockels cell for OEM applications, the STG-IMPACT. Once again, we set the industry standard - and at an exceptional price. In general, it operates below 1kHz. The STG-IMPACT employs the finest strain-free, highly deuterated KD*P available. Ceramic apertures ensure robust performance in demanding applications. Ultra-high-damage threshold Sol Gel and dielectric AR coatings are offered for a variety of laser wavelengths. The standard pin-type connectors (superior for high-voltage applications) provide quick connections and simplified design and assembly. Conventional threaded connectors are available as an option. The STG-IMPACT is back-filled with dry nitrogen.


  • OEM laser systems
  • Medical/cosmetic lasers
  • Versatile R&D laser platforms
  • Military & aerospace laser systems


CCI Quality - economically priced Exceptional value
Finest strain-free KD*P High contrast ratio
High damage threshold
Low 1/2 wave voltage
Single pass optical transmission >98%
Space efficient Ideal for compact lasers
Ceramic apertures Clean and highly damage-resistant
High contrast ratio Exceptional hold-off
Quick electrical connectors Efficient/reliable installation
Ultra-flat crystals Excellent beam propagation

Typical Specification

Electro-optical @ 1064nm
1/4 Wave Voltage: 3.3 kV
Transmitted Wave Front Error :<1/8 Wave
Capacitance: 6 pF
Sol Gel Damage Threshold @ 1064nm, 10ns pulse: 40J/cm2
Aperture 8 mm 9.25mm 10 mm 13 mm
Length 25 mm 37mm 39 mm 45 mm
Diameter 19 mm 25.3mm 25.35 mm 25.35 mm


  • STG-Impact 8 standard wavelength: 1064nm & 800nm
  • STG-Impact 10/13 standard wavelength: 1064nm & 755nm
  • The 1/4 wave voltage for any of our KD*P cells, @ 800nm, will be ~2.5KV, +/- 10%

2. STG-QX Series EO Q-switches

The STG-QX series sets the standard for KD*P electro-optic Q-switches. These devices provide reliable, stable performance for a diverse range of laser applications.

We offer a unique rebuild program that extends the STG-QX lifetime. All rebuilt units are upgraded with the latest product improvements and are returned with a new one-year warranty.

The standard configuration employs a broad band, high damage threshold Sol Gel AR coating for improved durability and performance. The STG-QX series is also available with index matching fluid and a choice of end caps. All units are tested for optic and electric function and are supplied with a QA inspection report.


  • Industry-proven performance
  • Dry or fluid-filled
  • Highest (99.9% KD*P) deuteration levels in industry
  • Adhesive/Epoxy-free assembly
  • Premium UV-grade fused silica windows
  • Apertures from 9.25mm diameter up to 19.5mm diameter
  • Lowest absorption in industry
  • High-reliability
  • Economical upgrade/rebuild program
  • Highest optical damage thresholds
  • Accessible technical support
  • Standard performance documentation
  • One-year limited warranty
  • Operation up to 10kHz (special order)


Typical Specification 99% KD*P STG-QX1020 STG-QX1320 STG-QX1630 STG-QX2035
Hard aperture diameter 9.25 mm 12.3 mm 15.1 mm 19.5 mm
Single Pass Insertion Loss <1.4% <1.4% <1.8% <2.0%
Voltage Contrast Ratio
(Cross polarizers) 5000:1 4000:1 3500:1 3000:1
(Parallel polarizers) 2500:1 1500:1 1800:1 1000:1
DC Quarter wave voltage @1064nm 3.5 kV 3.5 kV 3.5 kV 3.5 kV
Single Pass Distortion @ 633nm <λ/8 <λ/8 <λ/8 <λ/6
Capacitance @ 1 kHz 5pF 7pF 9pF 13pF
10-90% Rise time (50Ω line) 0.8 ns 1.1 ns 1.1 ns 1.5 ns
Outline dimensions
Diameter 34.8mm 39.7mm 41.3mm 46.2mm
Length 55.7mm 58.6mm 71.0mm 83.9mm

STG-QX1014A Short Path Length Pockels Cell

The newest model in the industry standard STG-QX series Pockels cell product line, the STG-QX1014A employs short path length components to reduce nonlinear self-focusing in higher peak power applications and temporal pulse broadening in femtosecond applications.

Attenuated crystal mounting minimizes acoustic artifacts when operating at repetition rates of up to 10kHz, or higher, depending upon the application. Employing internally sourced high-quality, low strain KD*P, the STG-QX1014A benefits from decades of electro-optic design and manufacturing experience.

The attenuation (damping) modification minimizes undesirable acoustic ringing effects, thereby permitting effective operation up to 10kHz. A variety of AR coating options are available, including our proprietary broadband 700-1000nm AR coating – ideal for minimizing round trip losses in Ti:Sapphire regenerative amplifiers.

Key Features

  • Short path length for operation up to 10kHz
  • Customized AR coatings including broadband AR for Ti:Sapphire applications, choice of optional wavelengths, ceramic hard clear apertures, low VOC construction materials and high-quality KD*P

Key Benefits

  • Reduced B-integral for high-damage threshold
  • High throughput (low losses)


  • Ultrafast regenerative amplifiers for spectroscopy; material processing; optical parametric amplification; femtosecond lasers for life sciences (e.g. LASIK) and material processing (e.g. photolithography mask repair)
  • Scientific research


  • Hard aperture diameter: 8mm
  • Intrinsic contrast ratio (ICR) @ 633 nm: >1200:1
  • Voltage contrast ratio (VCR) @ 633 nm: >450:1
  • Optical transmission @ coating wavelength: >98%
  • DC half-wave voltage @ 633 nm: £3.8kV
  • Transmitted wavefront error TWE (single pass distortion) @ 633 nm: £λ/8
  • Outline dimensions: Dia.34.8mm, Length 51.6mm

3. STG-CHIRON BBO Pockels Cell

STG-Chiron BBO Pockels cell raises the bar for high repetition rate and high average power laser applications. The STG-Chiron BBO Pockels cell design builds on the dual crystal geometry successfully used to minimize drive voltage (~2.3 kV quarter-wave voltage @1064 nm for the STG-Chiron). BBO Pockels cells operate from approximately 0.2 to 1.65 μm and are not subject to tracking degradation. Due to the low piezoelectric coupling coefficients of BBO, the Chiron 3 functions at repetition rates up to 1 MHz. STG-Chiron Pockels cells work in regenerative amplifiers, high pulse repetition rate micro-machining lasers, and high-average power lasers for material processing and metal annealing.

Key Features

  • High pulse rate operation to 1 MHz
  • Solid state – no index matching fluid
  • Low acoustic noise
  • Damage resistant ceramic apertures
  • Compact design
  • High-reliability
  • Operation at high average power

Key Benefits

  • Ideal for high average power systems
  • Low absorption leading to reduced thermal lensing/thermal depolarization
  • Exceptional high repetition rate performance
  • Excellent, accessible technical support


  • Military
  • OEM and replacement laser systems for machining, marking, via drilling; ophthalmology; Q-switching and regenerative amplifiers; research


  • Hard aperture diameter: 3.25 mm
  • Single pass insertion loss @ 1064 nm: < 1.5%
  • Intrinsic contrast ratio (ICR) @ 1064 nm: > 1000:1
  • Voltage contrast ratio (VCR) @ 1064 nm (parallel polarizers): > 500:1
  • Single pass wavefront distortion @ 1064 nm: <λ/6
  • LIDT1, 10 Hz @1064 nm, 10 ns, ~1 mm diameter: 10 J/cm2
  • Capacitance (DC): ~4 pF
  • DC half wave voltage @ 1064 nm: 4.3 to 4.9 kV
  • Temperature range exposure to simulate storage and shipping conditions:-25°C to 50°C
  • 10-90% rise time (theoretical) into 50 Ω line:~1 ns
  • Duty cycle in 1 s (applied voltage time / total time):<5%
  • Dimensions: dia. 25.3mm length 57.7mm

4. STG-TX Series KD*P Pockels Cells

STG-TX series KD*P Pockels cells are the most advanced large aperture optical isolators commercially available and are proven performers in high power applications. We are the leading producer of Pockels cells for the development of laser induced nuclear fusion and sub-micron microlithography. Nearly 300 units are in use worldwide; more than twice the total from all other manufacturers combined. We have incorporated state-of-the-art features, such as specially modified cylindrical-ring electrode geometries for optimum aperture extinction and transmission uniformity and minimum optical path length. Series STG-TX cells also feature axially adjustable windows for sub-millimeter control of window/crystal spacing and 224 TPI differential screws for arc-second adjustment of windows parallelism or net wedge. These units typically have a lifetime of many years and can often be rebuilt for a fraction of the cost of a new unit. Each unit comes with detailed 2-page/4-photo test documentation for quality assurance. We install premium 50 ohm GHV series electrical receptacles on series STG-TX cells because of their 20 kVDC and 1 GHz mil-spec ratings (used with RG-8 A/U or RG-213/U coaxial cable). We stock GHV bulkhead receptacles as well as cable-end plugs.


  • Axially adjustable windows for sub-millimeter control of window/crystal spacing
  • 224 TPI differential screws for arc-second adjustment of input/output windows parallelism
  • Double fill/drain ports
  • Individually accessible crystal faces for convenient inspection or cleaning
  • 50 C transmission line drive configuration is standard.
  • Precision milled and epoxy-free
  • A range of apertures available


  • Expanded beam allows for reduced intensity


  • Q-switching and optical isolators in pettawatt/terawatt lasers
  • Optical isolation and low frequency modulation of high power visible to NIR laser beams
Typical Specifications STG-TX2042 STG-TX2650 STG-TX3460 STG-TX5065 STG-TX7595 STG-TX100D
L x H x W (mm)1 85x80x85 97x87x92 102x95x103 115x111x119 151x136x144 157x 161x169
Hard aperture 19.5 mm 25.5 mm 33.5 mm 49.5 mm 73.5 mm 99.0 mm
Weight 1.1 kg 1.4 kg 1.9 kg 2.7 kg 5.4 kg 7.5 kg
Crystal deuteration2 95% 95% 95% 95% 95% 95%
OPTICAL (1064nm)
Single pass insertion loss 3.5% 4% 5% 5% 6.5% 7%
Voltage contrast ratio

Crossed polarizers

Parallel polarizers













Maximum residual birefringence (typically < 1% of aperture) < 10 nm < 12 nm < 18 nm < 20 nm < 40 nm < 80 nm
DC halfway voltage 6.4 kV 6.4 kV 6.7 kV 6.9 kV 7.3 kV 7.7 kV
Single pass distortion λ/20 λ/20 λ/20 λ/20 λ/20 λ/20
Capacitance @ 1 kHz 23 pF 27 pF 32 pF 56 pF 86 pF 115 pF
10-90% risetime 1 nsec <2 nsec 2 nsec 3 nsec 5 nsec 7 nsec
  1. L=housing length along optic axis direction; W=width between electrical terminals; H=height
  2. 99% deuterated KD*P and UV-grade KDP also available in certain sizes.

5. STG-IRX Series CdTe Pockels Cell

Initially designed to address the Q-switched CO2 laser market at 10.6μm, the cadmium telluride - based STG-IRX Q-switch may be configured to operate from 3-12μm. Its' high electro-optic coefficient and non-hygroscopic nature makes CdTe well-suited for this purpose. Through more than 30 years of electro-optic device design experience, we provide IRX Pockels cells with application-specific AR coatings or Brewster-cut ends, in apertures ranging from 3mm-10mm. The IRX Pockels cells are able to address applications beyond the spectral range of traditional oxide Pockels cells.


  • High electro-optic coefficient CdTe crystal
  • Available with apertures ranging from 3-10 mm AR coated or Brewster-cut crystals available
  • Environmentally isolated EO crystal
  • Customized versions available
  • Active cooling available (patent pending)
  • Operation from 3 μm-12 μm up to 100 kHz
  • Patent pending environmental control and high power water cooled option
  • Non-hygroscopic material
  • Low optical absorption


  • High contrast ratio
  • Operation over wide spectral range


  • CO2 laser Q-switching
  • IR pulse picking
Typical specifications STG-IRX3 STG-IRX4 STG-IRX5 STG-IRX7 STG-IRX9
Aperture diameters 1 3 mm 4 mm 5 mm 7 mm 9 mm
Optical transmission >98% @ 10.6 μm with 10.6 μm coatings
Intrinsic contrast ratio (ICR) @ 10.6 μm >500:1
Voltage contrast ratio (VCR) @ 10.6 μm >500:1
Single pass wavefront distortion @ 10.6 μm <λ/4
Spectral range of operation Must specify wavelength or band within 5-12 μm range
Optical transmission >98% @ 10.6 μm with 10.6 μm coatings
LIDT 2 2.3 J/cm2 , 1 mm diameter, 2.94 μm, 2 Hz, 100 ns
DC quarter-wave voltage (±6%) @ 10.6 μm ~4 kV ~5 kV ~6 kV ~7 kV ~9 kV
Capacitance (DC) ~ 6 pF
10-90% rise time (theoretical) into 50 Ω line ~0.3 ns
Duty cycle in 1 s (applied voltage time/total time) < 10%
Dimensions Dia 34.9mm, Length 92.7mm

1 Custom aperture sizes available

2 Recommended operation at 1/10 this fluence for increased longevity. LIDT will vary with wavelength and beam parameters.

STC Series Pockels Cells (Acousto-optic Q-switches)

1. STC Series BBO Pockels Cells

  • Minimal piezoelectric ringing
  • Low absorption
  • Broad transmission ranges from 200nm to 2000nm
  • Compact size
Part Number STC-BBO1.8 STC-BBO2.5 STC-BBO3.6 STC-BBO2.8
Dimensions 25.4×39 25.4×39 25.4×39 20X37.5
Clear Aperture 1.8 2.5 3.6 2.8
Crystal Size 2*2*20 3*3*20 4*4*20 3X3X20
Quantity of Crystals 1 1 1 1
Wavelength range 410-3500nm 410-3500nm 410-3500nm 410-3500nm
Quarter-Wave Voltage 2400 3600 4800 3600
Operation Wavelength 1064nm 1064nm 1064nm 1064NM
Electrodes Gold-coated PIN Gold-coated PIN Gold-coated PIN Gold-coated PIN
Insertion Loss <2% <2% <2% <2%
Extinction Ratio >1000:1 >1000:1 >1000:1 >1000:1
Capacitance >4 >4 >4 >4
LIDT@1064nm,10ns 10Hz 500MW/cm2 500MW/cm2 500MW/cm2 >600MW/cm2

Part Number STC-2BBO1.8 STC-2BBO2.5 STC-2BBO3.6
Dimensions (mm) 25.4×67 25.4×67 25.4×67
Clear Aperture (mm) 1.8 2.5 3.6
Crystal Size (mm) 2*2*20 3*3*20 4*4*20
Quantity of Crystals 2 2 2
Wavelength range 410-3500nm 410-3500nm 410-3500nm
Quarter-Wave Voltage (V) 1200 1800 2400
Operation Wavelength 1064nm 1064nm 1064nm
Electrodes Gold-coated PIN Gold-coated PIN Gold-coated PIN
Insertion Loss <2% <2% <2%
Extinction Ratio >500:1 >500:1 >500:1
Capacitance (pF) >4 >4 >4
LIDT@1064nm,10ns 10Hz 500MW/cm2 500MW/cm2 500MW/cm2

2. STC Series LiNbO3 Pockels Cells

Our optical grade LiNbO3 crystal has good electro-optic performance, large nonlinear coefficient, good optical uniformity, stable mechanical and chemical properties, no deliquescent, low half-wave voltage, and can be applied to high repetition rate operation. It is high in extinction ratio and laser damage threshold. LN electro-optic Q-switches are widely used in Er:YAG, Ho:YAG, Tm:YAG lasers, and are suitable for low-power Q-switched output, especially in laser ranging. We offer the most compact Q-switches for our customers. Furthermore, we also can custom-design and make the Q-switches according to your specific requirements to meet your various applications.

  • Large nonlinear optical coefficient
  • Large receiving angle
  • Small walk-off angle
  • Wide temperature and spectral bandwidth
  • High photoelectric coefficient and low dielectric constant
  • Non-absorbent, stable chemical and mechanical properties
Part Number STC-032855G1 STC-052855G1 STC-082855G1 STC-092855G1
Dimensions, LxWxH, mm 55x28x24 55x28x24 55x28x24 55x28x24
Clear Aperture, CA, mm 2.5 5 8 9
Crystal Size, mm 3x3x25 6x6x25 9x9x25 10x10x25
Quantity of Crystals 1 1 1 1
Wavefront Distortion λ/8@633nm
Quarter-Wave Voltage, V 885 1400 2400 2700
Operation Wavelength 1064nm
Electrodes Cu/Cr PIN
Insertion Loss <3%
Extinction Ratio >500:1 (LN); >200:1 (MgO:LN)
Capacitance, pF <5
LIDT@1064nm,10ns 10Hz >100MW/cm2(LN); >300MW/cm2(MgO:LN)

3. STC Series DKDP Pockels Cells

DKDP electro-optic Q-switches (Q-switch, Pockels Cells) are widely used in high-power, narrow-pulse (<10ns) laser systems due to their unique physical properties and excellent optical quality.

The DKDP crystal is a uniaxial crystal with excellent optical quality with an extinction ratio of >2000:1 (measured using a 632 nm He-Ne laser) with a wave front distortion of 98%. The DKDP electro-optic Q-switching capacitance is small (about 3-5pF), so that the rise time is short (<0.5ns), and a narrow pulse width laser beam can be achieved during Q-switching. Compared with the widely used electro-optic crystals on the market, DKDP crystals have higher damage thresholds (>1GW/cm2) under optical conditions of 10ns pulse width, 1064 nm wavelength and repetition rate 10Hz.

  • Wave front distortion: low capacitance
  • Short rise time: ~3pf
  • High transmittance: >98%
  • High damage threshold: >1GW/cm²
  • No static birefringence, no photorefractive damage
  • Anti-reflective coated quartz window
  • Resistant to ambient temperature shock and excellent electro-optic performance
Part Number STC-DK10 STC-DK12 STC-DK25 STC-DK30 STC-DK50
Dimension D25x39mm D25x39mm D55X80mm D55X80mm NIL
Clear Aperture 10mm 12mm 25mm 30mm 50mm
Quarter-wave Voltage 3200V 3200V 6500V 6800V 7500V
Electrodes PIN PIN Cu/Cr Cu/Cr Cu/Cr
Insertion Loss <2% <2% <2% <3% <5%
Extinction Ratio >2500:1 >2500:1 >155:1 >1000:1 >700:1
Capacitance <5 pF <5 pF <12pF <15pF <35pF
LIDT @1064nm, 10ns, 10Hz >800MW/cm2 >800MW/cm2 >850MW/cm2;

>1GW/cm2 @500ps


>1GW/cm2 @500ps


>1GW/cm2 @500ps

We can custom-design and –make specific Q-switches such as cubic outlook, nitrogen encapsulated, lead-wire electrodes etc as follows. Please send us your detailed requirements via email or phone.

RTP Electro-optic Q-Switch

RTP (Rubidium Titanyl Phosphate) is a robust electro‐optic crystal suitable for a wide variety of applications (such as Q‐Switches, Amplitude & Phase Modulators, Pulse Pickers, etc.) and operation in industrial, medical, and defense products. The crystal is transparent at most common visible and near infrared laser wavelengths. It performs well over a wide temperature range (from ‐500C to +700C) and at high repetition rates. RTP based Q‐switch devices are offered in matched pair configurations, in a temperature compensating design. When used for applications such as Q-switches and Amplitude Modulators, the crystals are mounted such that the input beam is polarized along the diagonal of the face. Our Q-switch is built using 2 RTP (Rubidium Titanyl Phosphate) elements in a temperature compensating design. The unique properties of RTP, including high electrical resistivity (~1012 Ω-cm) and a high damage threshold, result in a Q-switch with excellent properties.


  • High Damage Threshold: No Piezoelectric Ringing
  • Low Insertion Loss: Thermal Compensating Design
  • Non-hygroscopic


  • Transmission at 1064 nm: > 98.5 %
  • Half Wave Voltage at 1064 nm, for 9x9x25 nm Q switch: 1.3 - 1.5 KV
  • Contrast Ratio: > 20 dB
  • Clear Aperture: From 2x2 to 15x15 mm
  • Acceptance Angle: > 1 degree
  • AR coatings: R < 0.2% at 1064 nm
  • Damage threshold: > 600 MW/cm2 at 1064 nm (t=10 ns)

Part Numbers: STR-O-CR-L-E-W

STR means RTP EO Q-switches, O means the crystal’s cutting orientation (X/Y/Z), CR means cross section, L means crystal length, E means extinction ratio in dB (20, 23, 25 or 30), W means wavelength.

Selection Guide

Part number Crystal size (mm) HWV (kV) Part number Crystal size (mm) HWV (kV)
STR-Y-020-5-20-1064 2x2x5 1.3 STR-Y-020-10-20-1064 2x2x10 0.66
STR-Y-030-5-20-1064 3x3x5 2.0 STR-Y-030-10-20-1064 3x3x10 0.99
STR-Y-040-5-20-1064 4x4x5 2.6 STR-Y-040-10-20-1064 4x4x10 1.3
STR-Y-050-5-20-1064 5x5x5 3.3 STR-Y-050-10-20-1064 5x5x10 1.7
STR-Y-060-5-20-1064 6x6x5 4.0 STR-Y-060-10-20-1064 6x6x10 2.0
STR-X-020-5-20-1064 2x2x5 1.6 STR-X-020-10-20-1064 2x2x10 0.79
STR-X-030-5-20-1064 3x3x5 2.4 STR-X-030-10-20-1064 3x3x10 1.2
STR-X-040-5-20-1064 4x4x5 3.2 STR-X-040-10-20-1064 4x4x10 1.6
STR-X-050-5-20-1064 5x5x5 4.0 STR-X-050-10-20-1064 5x5x10 2.0
STR-X-060-5-20-1064 6x6x5 4.8 STR-X-060-10-20-1064 6x6x10 2.4
STR-X-070-5-20-1064 7x7x5 5.6 STR-X-070-10-20-1064 7x7x10 2.8
STR-X-080-5-20-1064 8x8x5 6.4 STR-X-080-10-20-1064 8x8x10 3.2
STR-X-090-5-20-1064 9x9x5 7.2 STR-X-090-10-20-1064 9x9x10 3.6

The graphs above show the behaviour of RTP and BBO Q switches at high repetition rates. In particular, the BBO shows Piezoelectric ringing at 30 kHz, while the RTP Q switch shows no ringing at this frequency. The BBO Q switch has a 2.5x2.5x25 mm element, while the RTP Q switch has two 6x6x7mm elements.