Pockels Cells

KD*P Pockels Cells

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, laser cavities incorporate Q-switches to shorten the output pulse, resulting in a light beam with enhanced peak intensity. Pockels cells come in two electrical configurations; transverse and longitudinal.  Our KD*P Pockels cell family of products is segmented into small aperture and large aperture models. The small aperture models include the QX, IMPACT, and CQX series whereas the large-aperture category includes the TX series. Transverse cells operate with the electric field perpendicular to the light beam. Because the light does not pass through the electrodes, these cells often employ opaque metal electrodes and the operating voltage is geometry dependent. G&H LiNbO3, BBO and CdTe Pockels cells utilize this design. (Lithium Niobate, LightGate and IRX series cells.)   Longitudinal cells orient the electric field parallel to the light beam. Some designs use face electrodes of transparent, conductive indium tin oxide (ITO), wire grids, metallic electrodes with a hole in the middle for the beam to pass through, or even conductive plasmas. An alternate approach positions the electrodes on the barrel of the cylindrical crystal, near the polished faces. This removes the electrodes from the beam path and, if properly designed, does not degrade the performance. G&H uses this approach in the product of its KD*P Pockels cells. (QX, CQX, IMPACT, and TX series cells.)   G&H offers the industry standard QX series, economical IMPACT cells, BBO-based LightGate, IRX CdTe IR, and large-aperture TX Pockels cell lines.    

QX Series

Widely accepted as the industry-standard KD*P Pockels cell, G&H has manufactured and continually refined the QX series Pockels cell since the 1980s. It is not uncommon to find a QX series Pockels cell still operating well over more than ten years after installation.  

Small-aperture KD*P Pockels Cells

G&H small-aperture KD*P Pockels cells include the IMPACT, CQX and QX series. Which small-aperture KD*P Pockels cell to use involves matching the clear aperture required and the repetition rate of operation to the appropriate device. 

IMPACT Series

For operation at 1kHz repetition rate or less, the unique construction of the IMPACT series enables OEM incorporation into applications such as medical and aesthetic laser systems.  

CQX Series

The CQX series employs manufacturing techniques similar to those of the IMPACT series, yet with external dimensions identical to those of the QX series. This makes the CQX cell a suitable retrofit/replacement for a QX series cell in cases where the repetition rate remains below 1 kHz. 

Large-aperture KD*P Pockels Cells

Designed to function as optical isolators, our TX series large-aperture KD*P Pockels cells protect the beam line by blocking back reflections in large scale laser platforms such as Petawatt lasers and/or laser fusion programs. We produce the crystals necessary to manufacture the devices required for this very demanding application in-house. 

BBO Pockels Cells

For high-average power and high repetition rate applications, our LightGate BBO Pockels cells are the preferred alternative to KD*P Pockels cells . The LightGate series BBO Pockels cell employs transverse electric field geometry with dual crystals to minimize drive voltage (~2.9 kV quarter-wave voltage @ 1064 nm for the 4 mm aperture LightGate 4).   BBO Pockels cells operate from approximately 0.2 - 1.65 µm and are not subject to tracking degradation. BBO, which we have grown since the 1980s, exhibits low piezoelectric response, good thermal stability, and low absorption. Due to the low piezoelectric coupling coefficients of BBO, LightGate cells function at repetition rates of hundreds of kilohertz.   LightGate series BBO Pockels cells are available in numerous configurations to address a diverse range of applications. These Pockels cells work in regenerative amplifiers, high pulse repetition rate micro-machining lasers and high-average power lasers for material processing and metal annealing.   We also provide single crystal cells, extra-long, reduced voltage cells, attenuated cells for applications requiring ultra-low piezoelectric response and cells with water-cooled apertures for high average power operation. 

Mid-Infrared Pockels Cells

Initially designed to address the Q-switched CO2 laser market at 10.6 µm, G&H’s cadmium telluride - based IRX Q-switch may be configured to operate from ~5 – 12 µm. Its high electro-optic coefficient and non-hygroscopic nature makes CdTe well-suited for this purpose. Through more than 40 years of electro-optic device design experience, we are able to provide IRX Pockels cells with application specific AR coatings in apertures ranging from 3 -10 mm. The IRX Pockels cells are able to address applications beyond the spectral range of traditional Pockels cells constructed of oxide based crystals and water-cooled designs increase the average power handling capacity 

Wavelength

Wavelength of operation	Electro-Optic Material
300nm-1300nm	KDP/KD*P
266nm-1650nm	BBO
400nm	LiNbO2
850nm-20000nm	CdTe

Repetition Rate

Maximum Repetition Rate (Pulse repetition frequency)	Electro-optic material
10kHz	KDP/KD*P*
100kHz	CdTe**
600kHz	BBO***

*For Microsecond length pulses, shoter pulses can raise the rep rates. **CdTe know goodto 100 kHz, upper bound unknown. ***Currently design limited by RF heading, R&D investigating solution.

Average power (for small aperture KD*P celss, ie 13mm down)

Average Power	Electro-Optic Material
< 10W	KDP/KD*P, BBO, CdTe
> 10W	BBO, low absorption KD*P (in specific cases), CdTe