Normalized transmission does not reach to 1 at resonant wavelength

Looking at the design all seems relatively well configured. I do notice you have the simulation set to run until you tell it to stop. Without the information regarding how many time steps you ran it is difficult to comment. The reason for this is that with a resonant structure it is critical to get the power out of the resonator and if you do not run the simulation long enough you will not get the expected result.

Do you have a screen shot of the time domain captured by the observation point?

Scott

Looking at the design all seems relatively well configured. I do notice you have the simulation set to run until you tell it to stop. Without the information regarding how many time steps you ran it is difficult to comment. The reason for this is that with a resonant structure it is critical to get the power out of the resonator and if you do not run the simulation long enough you will not get the expected result.

Do you have a screen shot of the time domain captured by the observation point?

Scott

The problem you are dealing with is you are not normalizing / setting up the simulation correctly. Note that your Gaussian has a half-width of about 1.3 but the waveguide section of your structure is only about 0.5? Which means any field component that does not couple into the waveguide is reflected at the PhC interface. You are not getting a power of 1 because not all the power is getting coupled into that waveguide.

Scott

The problem you are dealing with is you are not normalizing / setting up the simulation correctly. Note that your Gaussian has a half-width of about 1.3 but the waveguide section of your structure is only about 0.5? Which means any field component that does not couple into the waveguide is reflected at the PhC interface. You are not getting a power of 1 because not all the power is getting coupled into that waveguide.

Scott

There is no single answer to this and it depends on what you are attempting to demonstrate.

1. The efficiency of coupling a Gaussian beam coupling into the entire structure?
2. The efficiency of the structure once the signal is in the photonic crystal structure.

If it is the Gaussian coupling you place the source outside of the structure and the transmission you are measuring is what you get. However, you should realize that a Gaussian beam will not couple into this structure with anywhere near 100% efficiency so you should not be expecting a Transmission of 1.

If it is just to demonstrate that the structure efficiently propagates the signal you could leave your setup as is and then use 2 observation lines. One is your transmission line left as is while the other should be the same and located towards the beginning of the structure. What you could then do is export the power spectra from the two and manually normalize the output spectrum by the input spectrum. I have done a quick test of this and you get normalized powers around 1 after some post processing.

There is no single answer to this and it depends on what you are attempting to demonstrate.

1. The efficiency of coupling a Gaussian beam coupling into the entire structure?
2. The efficiency of the structure once the signal is in the photonic crystal structure.

If it is the Gaussian coupling you place the source outside of the structure and the transmission you are measuring is what you get. However, you should realize that a Gaussian beam will not couple into this structure with anywhere near 100% efficiency so you should not be expecting a Transmission of 1.

If it is just to demonstrate that the structure efficiently propagates the signal you could leave your setup as is and then use 2 observation lines. One is your transmission line left as is while the other should be the same and located towards the beginning of the structure. What you could then do is export the power spectra from the two and manually normalize the output spectrum by the input spectrum. I have done a quick test of this and you get normalized powers around 1 after some post processing.

When looking at the spectrum go up to the options button and choose to export the data.

When looking at the spectrum go up to the options button and choose to export the data.