A superposition test for the emergence of nonlinearities in a laser irradiated spherical absorber

The principal of linear superposition is investigated in the computational system of a solid spherical absorber immersed in a transparent aqueous medium and illuminated by a laser pulse. The absorber is exposed to a single top-hat pulse and to a fraction of the pulse from which a superimposed response is calculated. The results clearly show the transition of the system from a low fluence linear state where superposition is valid to a high fluence nonlinear state where the superposition is violated. The procedure described in the text can be used to find the transition to nonlinearity in a given excited system. This work can lead to better understanding and quantifying the transition from linear to non-linear regimes in complex systems.