In this example, we will study soliton propagation in an SOI waveguide.
Detailed descriptions of the simulation setup have been omitted in this example, please see the initial 1D Soliton example for further details on the simulation methodology.
In order to support soliton propagation, the linear dispersive, nonlinear instantaneous and nonlinear dispersive contributions need to be tuned accordingly. In this example of soliton propagation in a SOI waveguide, we will start by determining the linear dispersion the waveguide. The waveguide_neff_sweep.lms file contains the SOI waveguide based on the design in reference , and we will use the Eigenmode solver to determine the effective index and group-velocity dispersion (GVD) for this waveguide. After using the frequency analysis tool to track both the fundamental TE and TM mode (from 1.2um to 1.7um), the script D_to_GVD.lsf can be used to plot the GVD as a function of wavelength. The script will also export the "neff vs wavelength" results into a text file (neff_TM_like.txt), and we will use this information to model the linear (waveguide and material) dispersion of this waveguide in the subsequent time domain simulation.
1D FDTD Propagation with nonlinear material model
One could use the varFDTD solver to run a 1D FDTD simulation with the same effective medium, and add a nonlinear Raman and Kerr chi3 term. This simulation will account for both linear dispersion as well as the nonlinear Raman and Kerr effects. In the material database, a new "Sampled data" material "TM_like_neff" can be created using the "neff vs wavelength" results from the previous simulation. This can be as the base material for the "Chi3 Raman Kerr" model, which will allow us to incorporate the effect of linear material and waveguide dispersion from the FDE simulation on top of the nonlinear effects.
Note that chi3 value shown here is more for demonstration purpose. Users are encouraged to use values and parameters suitable for their experimental setups.
The varFDTD simulation would allow to observe the changes in the shape of the pulse at different propagation distances.
- P. Goorjian, A. Taflove, Direct time integration of Maxwell's equations in nonlinear dispersive media for propagation and scattering of femtosecond electromagnetic solitons, Optics Letters, Vol. 17, Issue 3, pp. 180-182 (1992)
- V.M.N. Passaro, F. De Leonardis, “Solitons in SOI Optical Waveguides”, Adv. Studies Theor. Phys., 2, 769-785, 2008