Figure 4

A schematic representation of the CCD, used to generate a lumped element model. Each ring resonator is modeled as a triangular cavity with mirrors that couple to two waveguides with leakage rate κ, and one fictitious mirror that represents intrinsic loss with leakage rate \(\gamma_{p/c}\). The cavity on the right is the plant and the one of the left is the controller. The driving signal w and the monitored signal z are indicated. The feedback signal u undergoes a phase shift ϕ and power loss η. The overall network has five input ports and five output ports, all of which are indicated; the driving field w enters at input port 3 and the monitored field z exits at output port 1; all input ports except 3 have vacuum fields. Note that there is a re-labeling of the ports with respect to Figure 1 in the main text.