Learning Forum

[anindya]

Dear Mr Guilin Sun,

I have been trying to simulate a medium with varrying refractive indices in FDTD and as per rule whenever I change the refractive index of a medium then it will introduce a shift in the source spectrum and I need to see that by placing monitors in both side of the medium.The first monitor will measure the source spectrum (frequency domain) before entering light into the medium and the second monitor will measure the spectrum of light coming out of the slab.Now if I continuous change the refractive index of the medium then by principle it should introduce a phase shift and as a consequence the shift in frequency spectrum may be observed by using these two monitors.What would be the best parameter or monitor to observe the shift in spectrum?Is it the transmission spectrum that may satisfy my need or I need to use a time monitor?I need a suggestion from you in this regard.I will be waiting for your response.

Thanks and regards,

Anindya Bose

 

[Guilin Sun]

Hi Anindya ,

I am not sure what does this mean "whenever I change the refractive index of a medium then it will introduce a shift in the source spectrum ".

In theory, the source spectrum is what you set, which should not depend on the device. In other words, any device should not change the source spectrum. However the output results, such as tranmission/reflection for periodic strcutures, or the phase (and magnitude) of the dominate E field component can change with device, in your case it is the change of the refractive index.

When the device is showing in the simulation, the result from the monitor in betwwen the source and the device is the net flow of incidence and reflection. Thus it does not measure the source. If you really want to measure the source spectrum, you can disable the device and do an empty simulation.

Please check what device you are simulating and what quantity is better to extract the information you need.