Learning Forum

[rsikder]

Hi, I am running 2D FDTD simulation using TFSF source for finding the transmission. Is it possible to direcly find transmission  using the TFSF similar to using Plane wave source? In TFSF source where should I place the monitor for finding the transmission?  Sometimes the transmission goes beyond 100%. If it is a normalization problem then how to normalized the source correctly in TFSF source?

[anna.wirth-singh]

Hello,

The normalization of the TFSF source can be tricky. Most transmission results are normalized to the power of the source, but this normalization may not be appropriate for the TFSF source. The fundamental problem is that an ideal plane wave has infinite power (since it has an infinite extent), while a single particle must absorb a finite amount of power. This article describes this issue and explains why normalizing to the source power can result in Transmission > 1: Tips and best practices when using the FDTD TFSF source – Ansys Optics

For the TFSF source, it may be more appropriate to normalize by the source source intensity rather than the source power. This page describes how to normalize by source intensity (note that special care should be taken if you will be injecting light at non-normal incidence): Understanding source normalization in the TFSF source – Ansys Optics

Do these resources answer your question?

Best,

Anna

[rsikder]

Hi Anna,

Thank you for your reply. I need to find the transmission using the TFSF source. However, the link that you have given it calculates the sigma by normalizing it with the source intensity. 

Transmission is calulated in Lumerical as:

 

So, my question is how to normalize the transmission using the source intensity since transmission is a dimensionless quantity.

Or, is there any way to calculate the transmission using the TFSF source?

Looking forward to your reply.....