The propagation of electromagnetic waves in general media is modeled by the time-dependent Maxwell's partial differential equations (PDEs), coupled with constitutive laws that describe the response of the media. In this work, we focus on nonlinear optical media whose response is modeled by a system of first order nonlinear ordinary differential equations (ODEs), which include a single resonance linear Lorentz dispersion, and the nonlinearity comes from the instantaneous electronic Kerr response and the residual Raman molecular vibrational response. To design efficient, accurate, and stable computational methods, we apply high order discontinuous Galerkin discretizations in space to the hybrid PDE-ODE Maxwell system with several choices of numerical fluxes, and the resulting semi-discrete methods are shown to be energy stable. Under some restrictions on the strength of the nonlinearity, error estimates are also established. When we turn to fully discrete methods, the challenge to achieve provable stability lies in the temporal discretizations of the nonlinear terms. To overcome this, novel strategies are proposed to treat the nonlinearity in our model within the framework of the second-order leap-frog and implicit trapezoidal time integrators. The performance of the overall algorithms are demonstrated through numerical simulations of kink and antikink waves, and third-harmonic generation in soliton propagation.Key words. Maxwell's equations, nonlinear dispersion, discontinuous Galerkin method, energy stability, error estimates.
Introduction.Nonlinear optics is the study of the behavior of light in nonlinear media. This field has developed into a significant branch of physics since the introduction of intense lasers with high peak powers. In nonlinear media, the material response depends nonlinearly on the optical field, and many interesting physical phenomena, such as frequency mixing and second/third-harmonic generation have been observed and harnessed for practical applications. We refer to classical textbooks [3,5,37] for a more detailed review of the field of nonlinear optics.Our interest here is in the development of novel numerical schemes for the Maxwell's equations in nonlinear optical media. Relative to the widely used asymptotic and paraxial wave models derived from Maxwell's equations, such as nonlinear Schrödinger equation (NLS) and beam propagation method (BPM) [3,5], simulations of the nonlinear Maxwell's system in the time domain are more computationally intensive. However, these simulations have the advantage of being substantially more robust because they directly solve for fundamental quantities, the electromagnetic fields in space and time. These simulations also avoid the simplifying assumptions that lead to conventional asymptotic and paraxial propagation analyses, and are able to treat interacting waves at different frequencies directly [28]. Recent optics and photonics research has focused on phenomena at smaller and smaller length scales or multiple spatial scales. For such phenomena simula...