1. Calculate the Mode Profiles at Specific Propagation Positions with BPM Mode Solver
To calculate the mode at a specific Z-position within the structure with BPM mode solver, set the mode_length variable to a specific value in the symbol table. This symbol does two things: it sets the Z-length of the mode calculation; and it artificially extends the structure at the Z domain min for the calculation. For this case, we have set mode_length to 1000. However, you can choose any value that works for your specific structure.
The most important parameters for SSC design are the taper length and shape. One common design approach is to calculate the overlap power along the propagation direction for both the input mode and output mode to see how the power couples within the device. The ideal design will convert most of input mode power into output mode power. Figure 2 shows calculated modes for both TE and TM at several z-cuts with different Si widths and heights. You can see that the profile has been changed from a Si-wire mode to an upper cover second core mode for both polarizations.