Advanced material models for dispersive, nonlinear and gain modeling using finite-difference time-domain (FDTD) methods are challenging due to the diversity of problems to be solved. A nonlinear model may be as simple as an instantaneous χ(2) or χ(3) effect, or may involve additional dispersive and anisotropic nonlinear terms. While it is relatively straightforward to provide a particular nonlinear material model appropriate for a specific application, it is a challenge to provide the wide range of different nonlinear material models that are required. In addition, it can be challenging to combine nonlinear responses with linear dispersion, which can be critical when considering issues such as phase matching.
Lumerical’s Flexible Material Plugins enable end users to develop new electric and magnetic FDTD material models. Users have the ability to modify the FDTD update equations in C++ to create materials with arbitrary nonlinearity and dispersion. These material models can then be complied as a plugin and added to the materials database. User defined materials are compiled dll or shared objects. One can define the properties of these materials directly from the GUI, and the FDTD simulation engine will automatically call the material plugin in order to update the electromagnetic fields as a function of time.
These plugins can be developed in several ways:
•By Lumerical and included in standard release
•By Lumerical to respond to end-user requests
•By the end-user with assistance from Lumerical
•By the end-user independently
The same plugins can be used in both FDTD and the 2.5D variational FDTD (varFDTD) solver in MODE. While FDTD provides the most accurate method for 3D nonlinear simulation, the simulation times are often much longer than for linear systems and can be prohibitive for larger geometries. For nonlinear and gain effects in waveguides, MODE can quickly simulate large nonlinear waveguide components.
FDTD simulation of quantum dot lasing in a photonic crystal cavity
MODE simulation of four-wave mixing in a racetrack resonator