The effect of thin coatings on second harmonic generation

The effect of thin coatings of nonlinear material on second harmonic generation is studied in this paper. Asymptotic expansions of the fields inside a thin nonlinear coating are performed. The convergence of these formal expansions is established. Our asymptotic analysis reveals the physical nature of this nonlinear problem. It also provides an effective method for overcoming the computational difficulties that arise in thin nonlinear coatings