Inverse medium scattering for a nonlinear Helmholtz equation

TL;DR

This paper addresses the inverse scattering problem for a nonlinear Helmholtz equation, demonstrating unique determination of the nonlinear refractive index and extending reconstruction methods with numerical validation.

Contribution

It introduces a theoretical framework for uniquely identifying nonlinear refractive indices and adapts existing reconstruction methods for nonlinear scattering objects.

Findings

Unique determination of nonlinear refractive index from far field data

Extension of factorization and monotonicity methods to nonlinear cases

Numerical validation of the proposed methods

Abstract

We discuss a time-harmonic inverse scattering problem for a nonlinear Helmholtz equation with compactly supported inhomogeneous scattering objects that are described by a nonlinear refractive index in unbounded free space. Assuming the knowledge of a nonlinear far field operator, which maps Herglotz incident waves to the far field patterns of corresponding solutions of the nonlinear scattering problem, we show that the nonlinear index of refraction is uniquely determined. We also generalize two reconstruction methods, a factorization method and a monotonicity method, to recover the support of such nonlinear scattering objects. Numerical results illustrate our theoretical findings.