RF MODULE

The figure below shows the z component of the Poynting vector for the fourth
eigenmode.
MODELING ERRORS AND SENSITIVITY ANALYSIS
Although the fundamental modes have converged to 5 decimal places, the known
modeling errors makes the exactness of the numbers uncertain. One major modeling
error is due to the fact that the model contains a plane strain assumption in a case
where the real-world model does not necessarily conform to this deformation state.
This modeling error is reduced in the refined model “Stress-Optical Effects with
Generalized Plane Strain” on page 277. Moreover, the material properties are only
known to a few decimal places and the computed magnitudes of the effective mode
indices will correspondingly be uncertain. A standard way of examining the effects of
uncertainty in material parameters is to perform a sensitivity analysis. That is, you
perturb one of the material parameters slightly and then examine the resulting
perturbation in the computed parameter. Another source of uncertainty is whether the
stress from the thermal expansion is large with respect to the other sources of stress in
the material originating from the manufacturing process.
276 | CHAPTER 4: OPTICS AND PHOTONICS MODELS