Dear Lumerical staff,
I have a number of questions about ring resonator/modulator model used in interconnect.
You may refer to the following example:
In this example the waveguide loss is setup as 7dB/m, which is 4e-4 dB/round trip intrinsic loss for a 60um long ring.
However I do suspect the unit should be 7dB/cm while 7dB/m means the ring is almost lossless.
Then the power coupling ratio of 1% is used, which after interconnect simulation shows almost maximized extinction ratio. However this does not make sense since only at critical coupling condition could max extinction be obtained and 1% coupling loss is over coupling this lossless ring.
I do feel this is problematic and please confirm if the waveguide loss unit is correct. Also I feel more comfortable with round trip loss like dB/round trip rather than dB/cm. Is there any way to define like that without converting roundtirp loss to dB/cm or dB/m?
For a ring modulator, most people choose to use single-bus ring rather than double-bus ring. However I saw most interconnect example used double-bus ring for modulation with only one bus waveguide connected to ONA. In that case does the frequency response give the spectrum same as single-bus ring (one coupling loss) or double-bus ring (two coupling loss)?
I see the coupling coefficient and waveguide loss as constant in the ring model. In reality they can be strongly wavelength dependent. Is there any way to specify wavelength dependent parameters (decomposing ring model with Mode waveguide can help but not sure how to define coupler properly)?
I saw many interconnect example specify non-equal neff and group index. It’s well known that this happens when where is dispersion but those examples all set dispersion to 0 as default. Do you think it’s necessary to find D and convert to proper unit to fill it or leave it as zero is also fine?