Ansys FDTD simulation for phase change due to reflection

[tanhanhbi]

TL;DR Summary

I set up the FDTD simulation to simulating the phase change due to reflection of difference materials. But the result is not similar with the reference paper

Hello,

I am currently simulating phase change due to reflection on gold (Au) using Ansys FDTD. My setup includes using a Frequency Domain Field and a Power monitor to observe the angle of the E-field in x-polarization. However, the phase change tendencies I'm observing do not match those in my reference paper.
My configuration: The yellow X is Frequency Domain Field and a Power monitor. The light source is 1um above the sample and the monitor is 1um above the light source

My simulation and reference paper.

Could anyone provide insights or guidance on how to improve my simulation?

Thank you.