Quadratic nonlinear optics to assess the morphology of riboflavin doped chitosan for eco-friendly lithography

We report the use of the Second Harmonic Generation response from a riboflavin doped chitosan film as a characterization method of the film morphology. This film is of particular interest in the development of new and bio-sourced material for eco-friendly UV lithography. The method allows us to determine how riboflavin is distributed as a function of film depth in the sample. This possibility is of importance in order to have a better understanding of the riboflavin influence in chitosan films during the lithography process. On the contrary, linear optical techniques provide no information beyond the mere confirmation of the riboflavin presence.