Laser profiling of defects in BaWO4 crystals

We present a setup for deep profiling of defects in transparent crystals using the laser beam. Optical inhomogeneities due to fluctuations in the index of refraction and scattering centres in four BaWO4 single crystals were measured by detecting the scattered light perpendicular to the incident laser beam. The depth profiling was achieved by moving the crystal along the laser beam and collecting the scattered light through a partly closed aperture. We have observed the region of the highest scattering from the beginning of the crystal to a depth of approximately 1 cm corresponding to the early stages of the crystal growth. Deeper inside in the crystal the concentration of the inhomogeneities is constant. The scattering in this region of relatively low defect density varies by less than one order of magnitude depending on crystal quality.