Polarization effects in a KGd(WO4)2:Nd crystal

Data are presented that demonstrate that, when a laser beam polarized at 45° to the vertical (horizontal) is passed through plane-parallel plates cut from a Nd-doped (4%) potassium gadolinium tungstate crystal and placed between crossed polarizers, the intensity and polarization of the transmitted light are periodic functions of the angle of incidence of the light. When scanned in two mutually perpendicular directions, the plates exhibit highly anisotropic transmission. The polarization at the intensity minima and maxima at the analyzer output is not orthogonal, in contrast to uniaxial crystals.