Beam splitter cubes can be used to obtain linearly polarised light from unpolarised light. These cubes split the incident light into s- and p- parts. Polarised light is used, for example, in material processing in order to produce precise edges in laser cutting. Linearly polarised light is also required in the assembly of isolators in order to avoid back reflections.
The splitting of light into its s- and p- parts can be achieved using an appropriate multilayer coating, or the property of birefringence within the substrate, on the incident light.
Polarisation Via a Coating
Plano-parallel plates or cubes are used to obtain a polarised beam via a multilayer coating. In this case, s- and p-pol beams are formed perpendicular to each other when exiting the cube, which makes optical setups much simpler.
In general, a distinction can be made between cemented cubes with high extinction ratios of 1000:1 and optically contacted cubes. The latter is suited for UV applications down to 248 nm as well as high laser power levels with damage thresholds of 10 J/cm² at 10 ns at 1064 nm.
Polarisation Via Birefringence
If higher extinction ratios are desired, it is necessary to use birefringent crystals such as calcite or alpha-BBO. Popular Glan Taylor and Glan Thompson prism polarisers can achieve 106 extinction ratios.
We would be happy to advise you as to which component is suitable for your application!
