Novel design approach achieves nonlinear photochromism using easy-to-synthesize rhodamine spirolactam derivatives

Photochromic compounds, which change their color when exposed to light, have been widely used as photo switches to control different properties of materials. Nonlinear photochromic compounds, characterized by a nonlinear response to the intensity of incident light, have attracted special attention among researchers as the nonlinearity leads to enhanced contrast and improved spatial resolution in photochromic reactions.