Model Wizard
These step-by-step instructions guide you through the design and modeling of the directional coupler in 3D. First, the simple geometry and the materials are defined. Then the lowest-order modes are determined. Those modes (the symmetric and the antisymmetric modes combined) are then used to excite the waveguide structure. In the next step, it is shown how you can change the sign of one of the modes to excite the other waveguide. Next, the bidirectional formulation for the Electromagnetic Waves, Beam Envelopes is used to model the two beating modes. Since, in this case, each mode will have a constant amplitude when propagating along the waveguide, a much coarser mesh can be used. The last part of the model demonstrates how to use the port input power and mode phase to approximate a given input target field.
Note:
These instructions are for the user interface on Windows but apply, with minor differences, also to Linux and Mac.
1
To start the software, double-click the COMSOL icon on the desktop. When the software opens, you can choose to use the Model Wizard to create a new COMSOL model or Blank Model to create one manually. For this tutorial, click the Model Wizard button.
If COMSOL is already open, you can start the Model Wizard by selecting New
from the File menu and then click Model Wizard
.
The Model Wizard guides you through the first steps of setting up a model. The next window lets you select the dimension of the modeling space.
2
In the Select Space Dimension window click 3D
.
3
In the Select Physics tree under Optics > Wave Optics, click Electromagnetic Waves, Beam Envelopes (ewbe)
.
4
Click Add and then click Study
.
5
In the Studies tree under Preset Studies for Selected Physics Interfaces, click Boundary Mode Analysis
.
6
Click Done
.
from the File menu and then click Model Wizard 
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