Photon Design CEO and founder Dr Dominic Gallagher surprised the crowd in Canada last week with live demonstrations of software MT-FIMMPROP. In his presentation Dr Gallagher simulated a cascaded set of MMIs, millimeters in length, on a standard laptop in seconds.

The key with Dr Gallagher’s example is the use of Sub-Devices; reusing the simulation result of identical waveguide sections. This feature is unique to frequency domain simulations such as MT-FIMMPROP’s EigenMode Expansion (EME). Without subdevices, there are 14 bend sections and 7 MMIs to simulate both posing computational challenges:

• The S-Bends have varying curvature meaning there are multiple unique cross sections, each needing a basis set of modes calculated in EME.
• The MMI sections require a larger mode lists to have a basis set that more accurately describes the field.

By using sub-devices, these 7 MMIs become just 1 simulation re-used and the 14 bends can be described by just 3 unique bend sections.

Of course MT-FIMMPROP sits atop decades of development in EigenMode Expansion, pioneered by Photon Design since 1998. EME lends itself well to long computational regions as it does not simulate on a uniform grid like the popular method FDTD. Instead it simulates multiple cross sections of a region and the modes supported there; if an MMI is 10 um long or 10 mm long, EME will take the same amount of time to simulate.

Dr Gallagher also discussed the great possibilities of a unified EM-simulator development continues - in particular the addition of other simulation methods. Dr Gallagher points out there are some simulations that require the move to an FDTD simulation; surface grating couplers, waveguide crossings, micro-ring resonators, and how different computational regions could have different methods in one device - a hybrid simulation. This would build on Photon Design’s track record with FDTD simulations in our software OmniSim, as well as modelling long distance thermal effects on waveguides that could be used in interferometer devices or tuning.