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[202121061699]

Hi,

When I used FDTD to simulate an add-drop microring resonator with a radius of 10um, I encountered the problem that the transmission of the DROP port cannot match the THROUGH port. According to the theory, the transmission of the DROP port, which is Tdrop should be 1-Tthrough, if the loss is negligible. And here I was using a Si waveguide, the radius of the microring is 10um. In this case, the bending transmission loss should be negligible, even if it is considered, it should not be too large, but the final transmission result I got shows that the DROP port are only about 0.7, as shown in the picture. Which is strange, because the upper and lower coupling regions of my micro-ring resonators are exactly the same, which means the coupling coefficients should be the same too, the Tdrop should be close to -0.95. So what is the reason that the transmission of the DROP port cannot match the THROUGH port?

I  also upload the picture about the structure of my resonator, the result of the time monitors in DROP and THROUGH port, and the mesh in the coupling regions. The simulation times in FDTD region was set to 40000fs, the mesh accuracy was 3 except the coupling region

This problem has been bothering me for a few days, can anyone help me out? Thank you sincerely

[Guilin Sun]

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