3D Ring Resonator Module

Directional couplers and ring resonators are ubiquitous in modern PIC design. Simulating them, however, tends to be a relatively time-consuming process, especially if you want to evaluate 3D vectorial effects such as polarization conversion. The 3D Ring Resonator module allows for a quick and simple calculation of the coupling between waveguides. The module uses a variant of Coupled Mode Theory that takes into account the varying distance and tilt between waveguides. 


Calculation of the transfer matrix of the coupler is fast once the modes of the waveguides have been calculated. Therefore, scanning a parameter like the horizontal (or vertical) gap between waveguides is very fast, allowing for easy evaluation of an optimal working point or even automated searches for the optimal gap for a desired coupling ratio.

The 3D Ring Resonator module can work with waveguides with arbitrary shapes: the exact shape of the waveguides before and after the main coupling section can be taken into account properly.


The module is very suitable for ring resonator coupler simulations, since the waveguide shape can be curved; however, any kind of coupling between near-parallel waveguides, for example in directional couplers or power taps, can be calculated.


  • Coupled mode calculations for
    • Any number of coupling (near-parallel) waveguides
    • Any number of modes per waveguide
  • Calculates the whole transfer matrix (transfer from each input mode into each output mode) in one go
  • Once modes are calculated, sweeping distances is quick
  • Easy to calculate ring resonator spectrum from the transfer matrices combined with group index information on the curved waveguides

Figure 1. Spectrum of a ring resonator that supports two modes.