Learning Forum

[anindya]

Dear Mr Guilin Sun,

I have designed an electrically tuned Silicon waveguide and I wanted to check its optical characteristics through FDTD simulation but unfortunately whenever I place the metal layer on the top of Silicon (waveguide structure) then I don't find much optical coupling in the silicon channel.However without the metal layer the light confinement through the channel is absolutely good.So I realize that the presence of metallic layer introduces a lot of reflection losses due to which I am unable to see the the impact of light gathering in the channel.Is there any way to reduce such losses with the presence of metal layer?Is there any requirement of using any other material in between to minimize losses in the FDTD simulation.Please suggest me a way to successfully resolve this matter because usage of metal is a must at this moment for the next phase of work.

Thanks and regards,

Anindya Bose

[Guilin Sun]

I am sorry to hear this.

First, please check if the source mode is correctly selected. When metal appears the mode source may not be able to automatically find the correct mode.  You may specify "near n" with value of the neff when there is no metal material.

Once the source mode is correct, please check imag(neff) or loss to see if it is too large. Attaching metal close to waveguide core can have very large loss such that the mode may propagate very short distance.  If this happens, please first move the metal away from the waveguide, check the mode and its loss. then gradually move down the metal and see when the loss is too large to propagate.

Please post some screenshots so I can understand your structure and settings easily.