Learning Forum

[Xinyu Liu]

no idea why the reflectivity of VCSEL is always higher than 1, as shown in the following picture. Is it a parameter problem or a software problem?

[Niki Papachristou]

Hi Xinyu,

Thank you for reaching out to us! Can you please provide more information on your simulation? A common reason to have ripples and tansmission higher than 1 is the fact that your simulation might not have been completed properly. This can be observed with the auto shut off level: Questions Regarding Autoshutoff level

I hope that was helpful, let me know if I can be of further assistance.

 

Please note that this is the optics forum and not the photonics where lumerical related question are posted. For you next lumerical question please post at: Ansys photonics forum

 

Kind Regards,

Niki

[Xinyu Liu]

Hi,

The parameter is set as follows. Is there any information you need?

[Niki Papachristou]

Hi Xinyu,

Thank you for sending me screenshots on your parameters. Can you please confirm that the status of the auto shut off level on the FDTD result view is 2? As in this example:

 

Kind Regds,

Niki

[Xinyu Liu]

the status is 1

[Niki Papachristou]

Hi Xinyu,

This means that you simulation has not ended properly, I would suggest to increase the simulation time:

Kind Regards,

Niki

[Xinyu Liu]

Hi

Before, the simulation time for FDTD was 3000 fs and actually I thought it was already enough. Then I tried 30000 fs and the reflection is still over 1. Do you think I need to increase it more?

[Xinyu Liu]

BTW, the status now is 2. Therefore, I think the simulation time is enough.

[Niki Papachristou]

Hi Xinyu,

Thank you for your reply. Another common reason is the boundary conditions. What type of boundaries condition do you have?

Kind Regards,

Niki

 

[Xinyu Liu]

Hi Niki,

For FDTD, x&y uses Periodic and z uses PML(step angle).

[Niki Papachristou]

Hi Xinyu,

It might be worth trying PML and adding some layers. However, this is hard to say without knowing your simulation. Can you send some screenshot of the structure?

Kind Regards,

Niki

[Xinyu Liu]

Hi Niki,

The structure is somehow like this picture.

Best,

Xinyu

[Niki Papachristou]

Hi Xinyu,

I was hoping for a screenshot from your simulation. Nevertheless, try the suggestion on PML layers. Also you can find more helpful instructions here:

Transmission Results Greater Than One

Kind Regards,

Niki

[Xinyu Liu]

Do you mean this screenshot? Because all my layers use objective defined dielectric, the colour is all the same.