Characteristics of Cornu depolarisers made from quartz and paratellurite optically active crystals

Cornu depolarisers made from quartz and paratellurite crystals have been studied. Numerical calculations and experimental data demonstrate that such depolarisers make it possible to significantly alleviate the major drawback to birefringent wedge depolarisers: the strong dependence of the polarisation of the output beam on the input polarisation orientation. We have examined the polarisation extinction ratio in the depolarisers as a function of the rotatory power of the crystals, depolariser length, beam diameter, and power distribution across the beam, and have determined the angle between the circularly polarised output beams in the far field. Data on the optical rotatory power of quartz and paratellurite crystals have been systematized, and the results have been used to derive dispersion formulas for these materials in the visible and near-IR spectral regions.