Learning Forum

[crossingsymmetry]

Hi,

I am going through the 1x2 MMI example provided by Ansys. In order to calculate S-matrix for TE and TM polarizations, the example simply selects symmetric and anti-symmetric boundary conditions on z min bc. In the provided example, the waveguide is a strip waveguide and I sort of understand why this work. In my case, I am using a rib waveguide which is not symmetric across z-axis. How would I for the EME solver to select TE or TM modes separately in order to extract s-matrix from the parameter sweep?

MMI example.

[Kyle]

If you would like to calculate the S matrix for both the fundamental TE and TM modes you can select the "fundamental TE and TM mode" mode selection option for the ports:

Don't use symmetry boundary conditions with this option so the solver can find both the fundamental TE and TM modes. For a 1x2 MMI this will calculate a 6x6 S matrix because there are 3 ports with two modes each.

[crossingsymmetry]

Hi Thanks for your response. I realized I would get the same answer as your example by selecting the "user selected modes" and it worked beautifully.

However, I run into new issues when I try to select modes for each port and run the simulation through ascript. Following is my script to sweep through TE and TM modes.
for (ii = 1:2){
switchtolayout;
# select modes
select("EME::Ports::port_1"); # select the port group
set("mode selection","user select");
set("selected mode numbers",ii); #mode 2 is TE
select("EME::Ports::port_2"); # select the port group
set("mode selection","user select");
set("selected mode numbers",ii); #mode 2 is
select("EME::Ports::port_3"); # select the port group
set("mode selection","user select");
set("selected mode numbers",ii); #mode 2 is TE
run;
}

However, when I run the simulation for both TE and TM, I get the following error.
Note that I have selected 1 or 2 for ports. The solution seems to be that each time I select a new polarizaiton, I need to press "Select Mode(s)", calculate modes, and then select mode number. Is there a way to do this automatically?
Thanks

[Kyle]

You can use the "updateportmodes" command to change the selected port modes in a script instead of using the set command to change the "selected mode numbers" property. The syntax for the "updateportmodes" command is given on this page:
Please try that and let me know if it helps.