The device, based on the polarization compensator first discussed by Berek in 1913, consists of a plate of uniaxial crystalline material with faces that are perpendicular to the optic axis. At normal incidence, the device is isotropic and introduces zero-phase retardance. The birefringence is varied with a rotation ring that tilts the plate. The orientation of the fast axis associated with this birefringence is adjustable with a second rotation stage. The two independent rotation scales, together with the provided curves, let you set the retardance from 0 to π for all wavelengths from 200 to 1600 nm.

The Berek’s variable waveplate can be directly mounted to an Optical Post or Pedestal Riser, but we recommend using it with our Opti-Claw adjustable 2 inch or our Standard 2 inch Mirror mounts. This allows you to align the waveplate so that it is truly normal to the incident beam, ensuring zero phase retardance and the accuracy of the wave plate.

You can use the Berek’s variable waveplate as a quarter-wave plate, a half-wave plate, or any arbitrary waveplate at any wavelength between 200 and 1600 nm. The wave plates have finely graduated dials to allow adjustable phase retardance between [min] and [max].

A basic optical isolator consists of a linear polarizer in front of a quarter wave plate, which converts linearly polarized light into circularly polarized light. Any unwanted light reflected toward the source will pass through the waveplate again, be converted to a linear polarization crossed with the filter. Isolators are important in many laser applications, where retroreflected light might destabilize a laser cavity. The Model 5540 may be configured to act as a quarter-waveplate in a lab application. Combining this with one of Newport's standard diameter sheet or Polarcor linear polarizers to quickly make an optical isolator for a laboratory experiment.

Our Berek's waveplates offer fine adjustment of a laser polarization state. A Berek’s waveplate may be used to compensate precisely for small phase shifts produced by other optics in your experiment. Vary the retardance and orientation of the waveplate to produce very small retardance until your system is optimized.

By using the Model 5540 as a half-waveplate, you can rotate the plane of polarization of a linearly polarized laser beam. Follow the waveplate with a linear polarizer to make a variable attenuator.