Nonlinear optical microscopy for artworks physics

Nonlinear optical microscopies (NLOMs) are innovative techniques recently introduced in the field of cultural heritage for the non-invasive in-depth analysis of artworks. In this review, we report on the state-of-the-art of NLOMs on different artistic materials, i.e., varnish, glue, paint, wood, parchment, and metal, and we evaluate the potential and capabilities of NLOMs in comparison with other more established linear optical techniques. We also discuss the latest studies defining suitable measurement conditions and instrumental requirements for the safe and in situ application of NLOMs on real cases.