RSoft Application Gallery Note: Modeling Coupled-Resonator Optical Waveguide (CROW)

Tool Used: OptSim Circuit

A coupled-resonator optical waveguide (CROW) device consists of a chain of coupled resonators in which light propagates with characteristics similar to a waveguide1. The application spectrum for CROW devices is interesting and broad, ranging from slow light and sensors to waveguides with controlled dispersion and bandwidth. OptSim Circuit’s ability to model feedback and bi-directional signal propagation makes it ideal for CROW analysis.

Figure 1 depicts a portion of a chain of the coupled resonators.

Schematic of the first two stages of coupled resonators in a CROW

Figure 1: Schematic of the first two stages of coupled resonators in a CROW

For this application note, two case studies are considered: CROW with (i) variable coupling and (ii) number of resonators. Figure 2 shows a 10-resonator structure.

Ten ring resonators coupled to create a CROW device

Figure 2: Ten ring resonators coupled to create a CROW device

Figure 3 shows OptSim Circuit simulation results for a CROW with 10 coupled ring resonators. The top plot shows passbands for different sets of outer- and inner-resonator coupling coefficients while the lower plot shows the effect of number of resonators for fixed outer- and inner-resonator coupling coefficients.

Passbands for different coupling coefficients
Passbands for number of resonators

Figure 3: Passbands for (a) different coupling coefficients and (b) number of resonators

The simulation results are in excellent agreement with those reported in the referenced paper. Additional effects that can be included in the analysis are waveguide dispersion, wavelength dependent coupling, defects, and more. For more information, please contact RSoft Technical Support.

Reference

1 J. K. S. Poon, J. Scheuer, Y. Xu, and A. Yariv, “Designing coupled-resonator optical waveguide delay lines,” Journal of Optical Society of America (JOSA) B, Vol. 21, No. 9, 2004, pp. 1665-1673.