Transmission of photonic crystal with Micro RIng Resonators.



Most of the example given for Photonic Crystals using Lumerical FDTD use diople source instead of Mode source (like finding bandgap, dispersion diagram and transmission etc.). However, most of the example given for Phototnic Integrated Circuits (like Micro Ring Resonators) use Mode source instead of dipole source. If I have a structure where both Micro ring resonators and photonic crystals are present simultaneously (like in the research paper, open access,, how should I proceed to solve for the transmission of the composite structure. I can mail my file if required.

Thanks and Regards


Dear @awanish

Dipole sources are used if you want to study the resonance modes of a cavity. Your cavity can be a microring or PC cavity. However, if you want to study the coupling between a waveguide and cavity, use of waveguide modes are preferred. This means that use of dipole source or waveguide mores depends on the parameter that you want to measure not on the geometry

In your setup, what you want to study? Resonance modes or transmission?



Hi @bkhanaliloo

Thanks for quick reply and the details.
I want to find both, resonant modes and transmission. I made my design similar to our experimental setup and getting expected transmission from the solver so the transmission problem is solved now. However, for finding the resonant modes using dipole source, I have few doubts. It would be of great help if you can please direct me to some online examples or provide me the details. Here are my queries:

  1. How many dipole source should I use to excite all the modes of cavity?
  2. How to find resonant modes, the wavelength where the cavity is resonant, using dipole source? Is there any specific monitor I should use?
  3. The example given on website tries to find out Q-factor and resonant wavelength using “Q-Analysis” structuere group. How to use or create such groups for my own design?

Thanks and Regards


Hi @awanish

I am glad your transmission plots are working as expected.

  1. I guess 5 dipole would be a good start. By randomly locating them inside the cavity and repeating the simulation for a few times should discover all the supported modes by the cavity.

  2. This direct should provide you with a simulation file (called Tang-cavity.fsp) that includes resonant finer and mode profile analysis group.

  3. I guess starting here will be quite useful to see in depth detail how we do PC cavity simulations, an an example. Modeling instruction explains how you can add such an analysis group.