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OmniSim FDTD

Omni-directional photonics FDTD simulations

Active FDTD

Add carrier dynamics to your FDTD model

Photon Design offers the World’s first commercial active FDTD tool adding the ability to model semiconductor gain within an FDTD engine. Now you can at last model photonic crystal lasers and other micro-cavity lasers realistically.

Gain models

The Active FDTD module supports two different gain models: 

  • The Dynamic Gain model, in which the gain is function of the carrier density. This model accounts for current injection, spontaneous and stimulated recombination rates. For this model the user needs to provide gain curves (either from experiment or simulated using e.g. Harold), which are then fitted with our Wide-Band Gain model.

  • The Static Gain model, which does not explicitly consider a carrier density in the device but rather uses a saturable gain model in which the gain is a function of intensity. In this case the user can simply define the gain function as a sum of Lorentzian functions whose amplitude, position and width can be specified. 

Active FDTD simulation

Littrow lasing simulated in a W15 line defect constructed in an InGaAsP QW material
and electrically pumped. The simulation includes a dynamic carrier model. 

  • Dynamic Gain model:

  • Rate equation model of carriers including spontaneous recombination, stimulated recombination, injection current.

  • Wide-Band Gain model, with automatic fitting to a set of gain curves (g(l) at a set of different carrier densities).

  • Convergence Acceleration – normally the spontaneous lifetime is too long to model in FDTD (would require too many FDTD time steps). Convergence Acceleration gets the device into the correct steady state more quickly.

  • Static Gain model:

  • Saturable gain model.

  • Gain function defined as sum of user-defined Lorentzian functions.

  • Very simple to use.

  • Fully integrated into the OmniSim and CrystalWave user-interfaces.

  • Almost all features of the FDTD engine available (excluding sub-gridding – possibly available in a future version).

  • Current injection is controlled by an Editor mask-layer, allowing you to readily inject current anywhere you want.

  • All gain-material parameters are stored in a standard Photon Design material database file (.mat).

  • Speed: in general the gain material is confined to a small layer – a fraction of the total simulation volume. Therefore the module does not significantly slow down the simulation speed.

Applications include photonic crystal lasers and VCSELs.


Download Active-FDTD specifications