Simulation of Optical and Photonic Systems
Waveguide and Thin Film Simulation
Numerical methods and modelling techniques are gaining importance in the design of optical systems. In the photonics group we are particularly interested in the modelling of fiber, integrated optical components and miniaturised optical components and systems as well as in the optical thin film technology. We use the following simulation software packages: Ray-Tracing Software ZEMAX, wave-optical Photonics Component Design Suite by RSoft, thin film simulation program TFCalc and FilmStar.
Ray Tracing (Zemax)
The term ray-tracing simulation in optic's design usually means a sequential ray tracing. In sequential ray tracing a few rays are "traced" through an optical system of a sequence of boundary surfaces. These simulations are used to determine the imaging properties of an optical system. In most cases we use the non-sequential-mode of Zemax for the ray optical simulation of waveguide geometries. It allows the propagation of rays through any geometry and the detection at user definable positions in a 3D CAD-space. These simulations are used to gain information about the efficiency of an optical system or the light distribution at a certain spot of a 3D geometry. To get significant data the measured structures need to be at least 10 times the size of the wavelength. Therefore the ray tracing method is not suited for the design of diffractive or waveguiding structures with a low number of modes.
Wave-Optical Simulations (Synopsys - RSoft Photonic Design Software)
The company RSoft Component Design Suite of Synopsys is a widely used simulation tool for designing photonic's components. In the course of a CTI-project (Commission for Technology and Innovation) the following tools have been acquired:
- Grating MOD
BeamPROP is used for the modelling of single-mode waveguides or fibers. There are two methods available. The mode-solver allows to calculate the energy distribution along the waveguides cross section. The beam propagation method on the other hand can model the field distribution across the desired component. BeamPROP can solve 2D as well as 3D problem.
FullWAVE is based on the "Finite-Difference Time-Domain" method (FDTD) opens up a broad range of applications. The FDTD is even able to model the feedback of electromagnetic waves by solving the Maxwell equations. This is of particular interest in the field of surface plasmons and biophotonics.
DiffractMOD is based on the "Rigorous Coupled Wave Analysis" method (RCWA). It is of particular interest for diffractive structures like diffractive optical elements (DOEs) and waveguide resonators.
GratingMOD is based on the "Coupled Mode Theory" (CMT). It is mainly used to calculate and analyse Bragg gratings. Furthermore it is suitable for "long-period" gratings and the design of optical amplifiers.
FemSIM is used for the calculation of waveguide and resonator modes of any structures. It is based on the Finite Element Method (FEM).
Thin Film Simulation (FilmStar)
The calculation and modelling of reflective and transmissive properties of thin film systems are based on the Fresnel equations. With the use of matrix algorithms the spectral performance at various incident angles can be calculated. One can even determine the associated colour to the spectrum in the CIE colour space. The TFCalc software package is used to model of anti-reflective, mirror or filter coatings. For more complex tasks like optimization or the analysis of existing spectral curves we use the software package Filmstar by FTG.