Modeling coherent nonlinear microscopy of axially layered anisotropic materials using FDTD

Providing quantitative interpretation of coherent nonlinear microscopy images, such as second-harmonic generation (SHG) or third-harmonic generation (THG), can often be hampered by the complex phase-matching conditions, especially in the presence of sample linear heterogeneity. We recently presented a numerical pipeline using the finite-difference time-domain (FDTD) method to take this heterogeneity into account for THG microscopy. However, due to software restrictions, we only considered nonlinear materials with diagonal nonlinear susceptibilities. We now expand the recently developed FDTD approach to model second-order and third-order nonlinear microscopy for anisotropic, non-diagonal materials that obey Kleinman Symmetry, organized in layers along the optical axis, and validate our simulations on well-described geometries.