Schlieren imaging of bulk scattering in transparent ceramics

Abstract

Bulk scattering in polycrystalline laser materials (PLM), due to non-uniform refractive index across the bulk, is regarded as the primary loss mechanism leading to degradation of laser performance with higher threshold and lower output power. The need for characterization techniques towards identifying bulk scatter and assessing the quality. Assessment of optical quality and the identification of bulk scatter have been by simple visual inspection of thin samples of PLMs, thus making the measurements highly subjective and inaccurate. A modified white light Schlieren Imaging Setup utilizing variable focusing capability is demonstrated. The white light Schlieren Imaging Setup makes it possible to image the spatial variations in the refractive index in the PLMs regardless of dimensions, which are the cause of bulk scattering loss in a transparent material over the entire cross-sectional area of the sample. The high sensitivity of white light Schlieren provides the ability of directly imaging the local spatial variations in refractive index across the entire sample dimension and compare different samples.