Nonlinear thickness dependence of two-photon absorptance in Al2O3 films

Abstract.

Linear and nonlinear absorptance in Al₂O₃ films of different optical thicknesses are investigated using an ArF laser calorimeter. While the linear absorptance at 193 nm shows the expected linear increase, nonlinear absorptance increases quadratically with increasing film thickness. Thus, it cannot be described by a constant nonlinear absorption coefficient β. The experimental findings are explained by a simple phenomenological approach using excited states with a finite interaction length longer than the actual film thickness. a new material constant Γ is introduced, which describes the nonlinear absorptance behavior correctly.