Pockels Cells are electro-optic devices used to switch the polarization direction of light beams. Their operating principle is based on the Pockels Effect, by which an applied electric field produces linear changes in the refractive index of non-centrosymmetric crystalline materials. Because their switching behavior largely depends on the drive electronics, Pockels Cells offer a much faster response time than acousto-optic devices.


Common applications for Pockels Cells include:

  • Q-switching of laser cavities
  • Coupling light in and out of regenerative amplifiers
  • Light intensity modulation, when used in conjunction with a pair of polarizers

Pockels Cells can also be used for phase modulation—by imprinting sidebands onto the frequency of the transmitted light at multiples of the cell’s drive frequency. This electro-optic approach, however, modulates phase less efficiently than devices that rely on optimized crystal orientation and electric field direction.


The ideal crystalline medium for Q-Switch Crystals depends on operating wavelength laser beam size, damage threshold, average power handling, contrast ratio, extinction ratio and repetition rate. Here’s an overview of different types of Q-Switch Crystals:

  • KD*P Pockels Cells are routinely used for Q-switching applications with wavelengths from the UV to approximately 1.1 µm. Beyond 1.1 µm, absorption limits KD*P’s use in active cavities unless the application can tolerate a few percent of absorption.
  • LiNbO3 Pockels Cells address wavelengths of at least 1.064 µm. With an electric field applied transverse to the direction of light propagation, LiNBO3 cells can be configured to operate at a lower voltage than comparable KD*P cells. LiNbO3 can also be a good choice for infrared wavelengths as long as 4.0 µm, though half-wave voltage increases at those wavelengths.
  • BBO Pockels Cells target operating wavelengths from the UV to roughly 2 µm. BBO crystal handles high average powers better than either KD*P or LiNbO3. Since it has a relatively small electro-optic coefficient, BBO tends to require higher voltages than the other two crystal mediums. The voltage required in a given application will depend on the crystal length, thickness and size of the clear aperture.