Berek’s variable waveplates modify the polarization of collimated beams from any state to any other state with the flexibility, convenience, and precision previously found only in bulky and expensive Soleil-Babinet compensators. True zero-order retardance, minimal wavefront distortion, and beam displacement of less than 150 µm are all featured at an economical price.
- Soleil-Babinet compensator performance at a much lower cost
- Variable zero-order retardance
- Ideal for removing arbitrary ellipticity in your experiment
- Combine with a polarizer to create or analyze any polarization state
- Angular sensitivity equal to Soleil Babinet
- Less than 150um beam displacement
Features Based on Polarization Compensator First Discussed by Berek
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.
Berek's Wave Plate Mounting
The Berek’s variable waveplate can be directly mounted to an Optical Post or Pedestal Riser, but we recommend using it with our 9854 Opti-Claw adjustable 2 inch (50.8 mm) mount. 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].
Basic Isolator Applications
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.
Polarization Compensator Applications
Our Berek 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.
Variable Attenuator Applications
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.