Learning Forum

[minusunny]

Hi,

I am trying to simulate my device by illuminating two ports at the same time. Is it possible to simulate two ports in FDTD?

[Afroditi Petropoulou]

Hello,

 

When using ports in FDTD only one port can be used as a source at the same time as explained in Ports (FDTD) - Simulation Object – Ansys Optics.

If you need to get results with different ports enabled, you can use S-parameter matrix sweep in the "Optimizations and Sweeps" tab. There you can enable the "Excite all ports" option. In this case the sweep will launch as many simulations as there are defined rows in the S-Matrix Setup table, effectively exciting all modes in all ports (but again two ports will not be enabled at the same time). When the "Excite all ports" is un-checked, the user can selectively choose which ports and modes to excite. You can find more information in S-parameter matrix sweep utility – Ansys Optics.

 

Best Regards

Afroditi

[minusunny]

Hi, So the value of power that I am getting from the port and the value of transmission is different. Why is this happening? When i check the value of T i get 20% whereas when i take abs^2(s) i get 0.0001 .  How can i get the value of transmission from the s-parameter sweep utility?

 

[Afroditi Petropoulou]

Hello,

Could you please tell me which are the values that you are comparing?

Let's assume the following example:

If you have port 1 as your source and you want to check what you get in port 2, the results that should match are abs(S)^2 with abs(T_out) of port 2 (same for port 1). Do these results match?

You can find more information about ports in Ports (FDTD) - Simulation Object and Using and understanding Mode expansion monitors

 

Best Regards,

Afroditi

[minusunny]

 

No they are different. Please see the results:

Abs(T) = 90% whereas abs^2(S) = 5.4e-10

[Afroditi Petropoulou]

Hello,

The results that you have plotted are from the "expansion from plot monitor"?

The results that should match are the following:

If you are looking at the "T" result (which is the same as the T_total result from the expansion for port monitor) you will not get the same results as abs(S)^2, since S gives you the power that reaches the port from other ports. For example if you are looking at the port that is used as a source, the T result will be close to 1 (since light is injected from this port) but S result could be almost 0 as it is the result of the reflected light that gets back to this port. T_out result though, is the transmission at the direction of the red arrows shown above, which is what S parameter calculates. 

If T_in result at the source port is not exactly equal to 1, but 0.99... then the results that would match are abs(S)^2 of a specific port with T_out of the specific port devided by the T_in of the source port.

Best Regards,

Afroditi