## Photonics

Topics related to Lumerical and more

#### Elliptical Gaussian beam for mode overlap

• Ekaterina Pshenay-Severin
Subscriber

I need to calculate the mode overlap between a WG mode and an elliptical Gaussian beam. I would like to do it in MODE using overlap. How can I create an appropriate object with an elliptical Gaussian field profile? I use "rectilineardataset" to generate the filed distribution but I don't understand how copy it to a DECK.

Ekaterina

• Guilin Sun
Ansys Employee

Unfortunately it is difficult to load ldf data into the Global deck as it only accept save dcard data. You can use  zbf data: https://optics.ansys.com/hc/en-us/articles/360034928293-zbfwrite-Script-command

I tried and it works.

You can also use script to calculate the overlap as you have already the elliptical beam data. What you need is to get the mode fields:

E=getresult("mode1","E");

H=getresult("mode1","H")

and then get components, and follow this link for the formula: https://optics.ansys.com/hc/en-us/articles/360034405254-overlap-Script-command

• Ekaterina Pshenay-Severin
Subscriber

Thank you a lot for the answer! But I still have a question. Firstly, the additional issue I face is that the WG I simulate with MODE is oriented along the x-axis (injection x-axis). To use overlap, I need the elliptical beam in the Y-Z plane. Of course, I can rearrange the WG geometry, but I wanted to find out if there is a way to generate an elliptical beam in the Y-Z plane.

Concerning zbf, it seems that the zbf export works in a way that the resulting field distribution is in the X-Y plane. Actually, I tried this approach by following the tutorial: "Import Source in Ansys Lumerical FDTD" (https://courses.ansys.com/index.php/courses/lumerical-fdtd-sources/lessons/import-source-in-ansys-lumerical-fdtd-lesson-7/). I defined the source and the monitor so that x is the injection direction and saved the field from the monitor to the zbf. However, when I import it to the DECK in MODE for the overlap analysis, the field is in the X-Y plane.

Is there is a way to get field in zbf in Y-Z plane ?