We present a characterization technique to assess the quality of 4H-SiC CVD growth process based on optical methods. The setup allows characterizing the epilayer and the substrate at the same time, leading to a self-consistent determination of the epitaxial layer quality with respect to the substrate. By using high power density UV optical pumping to stress 4H-SiC epitaxial layers, we are able to check the generation and evolution of Single Shockley faults on large areas, without fabricating bipolar junctions. This characterization technique is a fast and non-destructive method to compare the quality of different 4H-SiC CVD growth process.