The predictive quality of microscopic modeling can be verified or disproved by optical-gain measurements. If the design is approved, one may continue to laser production. If experiments exhibit unexpected gain features, one can refine the modeling by including systematically new effects. As more effects are included, the predictive power of the model increases. In general, a closed-loop design, where the modeling and experiment are replaced cyclically, has proven to be a very efficient method to find and develop new laser designs with desired performance.
