Measure by interferential conoscopy of the phase distribution acquired from conical diffraction

Abstract We have measured the Pancharatman phase difference between the electrical field emerging from the conical diffraction (CD) phenomenon in the KGd(WO2)4 (KGW) biaxial crystal and a vertical polarized reference, each field traveling in one arm of an interferentiel conoscope. This phase is obtained as the retardation introduced by a liquid crystal retarder in the reference beam which maximizes the interference intensity for each camera pixel. The full characterization of the U ˆ k x , k y operator describing the CD was obtained including polarimetric measurements. We have found that the azimuthal variation of the eigen-values of the dielectric tensor was responsible for an azimuthal variation of the phase of the U ˆ operator. The link with the orbital angular momentum of the beam is provided in the cases of a uniformly polarized field and in a vector field.