We would like to model our laser in an RF module, solving for electrical field strength, to see the optical field distribution as a function of layer thicknesses, however we kept seeing unexplainable discontinuities in mode distribution when we would remove a layer or leave only a thin layer (~10nm)
One thing that changes with these thin layers is the mesh size in these thin layers. Therefore we checked whether for a fixed design (without thin layers) the results would change if we change our mesh size. The results can be seen in the attached file for 2 mesh sizes, for the exact same geometry (the three layers in the middle are 300, 250 and 300nm thick (with a step in the bottom one). As can be seen both the mode shape and the effective mode index calculated by Comsol do not change significantly. However, upon decreasing mesh size (the right of the figure) the calculated electric field strength keeps increasing, as can be seen by the encircled maximum E-field value. As can be seen this changes by a factor of almost 2 over this mesh-size variation, well outside numerical approximation range.
Plotting the number of mesh elements versus the Electric field yields the graph that is also shown in the attached picture.. Is there a reason we are missing that Comsol gives values this much higher for smaller grid elements? If so, what model settings could be involved?
One thing that changes with these thin layers is the mesh size in these thin layers. Therefore we checked whether for a fixed design (without thin layers) the results would change if we change our mesh size. The results can be seen in the attached file for 2 mesh sizes, for the exact same geometry (the three layers in the middle are 300, 250 and 300nm thick (with a step in the bottom one). As can be seen both the mode shape and the effective mode index calculated by Comsol do not change significantly. However, upon decreasing mesh size (the right of the figure) the calculated electric field strength keeps increasing, as can be seen by the encircled maximum E-field value. As can be seen this changes by a factor of almost 2 over this mesh-size variation, well outside numerical approximation range.
Plotting the number of mesh elements versus the Electric field yields the graph that is also shown in the attached picture.. Is there a reason we are missing that Comsol gives values this much higher for smaller grid elements? If so, what model settings could be involved?