OmniSim FDTD

FDTD Simulation Software with OmniSim

Part of our state-of-the-art FDTD and FETD time-domain toolkit

The OmniSim and CrystalWave frameworks includes a highly efficient FDTD (finite difference time domain) engine to simulate the propagation of light through your designs. FDTD is ideal for modelling complex optical structures including ring resonators, optical gratings, photonic crystals and nano-photonics.

The FDTD engine is part of our time-domain toolkit, which also includes our unique FETD engine for accurate modelling of plasmonics and nano-antennae.

Overview of our FDTD engine

• 2D and 3D FDTD engine

• Multi-core, multi-CPU FDTD calculations and cluster support

• Native 64-bit version: virtually unlimited memory

• Advanced material models

• Unique sub-gridding tool

• Active FDTD algorithm for nano-lasers

• Very fast speed optimised algorithm

• More memory efficient than competing products, featuring advanced memory reducing techniques (including running transform as an alternative to Fourier transform)

• Real-time field visualisation during the calculations

Finite Difference Time Domain (FDTD) simulation of a photonic crystal Y-junction

FDTD Sub-Gridding

Photon Design's unique sub-gridding tool gives you the ability to create 2x, 4x or greater increased resolution in localised regions. 4x sub-gridding can accelerate a 3D simulation by up to 64x. This is vital in plasmonics for modelling thin metals or small objects accurately, e.g. Mie scattering on metal nanoparticles.

Resolution of the FDTD Engine increased locally with a sub-gridding region
(the boundary of the sub-gridding region is shown with a white line)

The main benefit of sub-gridding against uniform and non-uniform grids is shown below. In this case the grid needs to be refined around the surface of the nanoparticles. With a non-uniform grid, large regions of the device still need to use a refined grid unnecessarily. The use of sub-gridding regions allows to only increase the grid density where needed, optimising calculation time.

Benefits of sub-gridding against uniform and non-uniform grids.

Innovative research work in partnership with Oxford University allowed us to solve the problem of reflections usually associated with sub-gridding in FDTD. The graph below shows the extremely low reflection coefficient generated by our sub-gridding formulation for frequencies ranging from 10 to 1000 THz.

Anomalous reflection coefficient generated at the main-grid to sub-grid interface.
Ideally it would be zero. The graph shows an excellent low reflection coefficient
of better than 1e-8 for a wide range of optical frequencies.

Materials

• Supports transparent and lossy materials - users can specify fixed refractive index and attenuation

• Extensive material database with standard dielectric materials and metals

• Dispersive materials models including Debye, Drude and Drude-Lorentz models - and automatically generate model parameters (fitting) from a supplied dispersion spectrum.

• Non-linear materials including chi2 and chi3 (see example here)

• Anisotropic refractive index - general symmetric tensor

• Magnetic materials

• Negative refractive index materials

Boundary conditions

• High performance PMLs on all six faces

• Dispersive PMLs e.g. to match metals touching the boundaries

• Metal (PEC), magnetic (PMC) and periodic boundary conditions

Sources

• Mode excitor: built-in mode solver for excitation of waveguide mode

• Dipole excitor: single dipole source or volume of incoherent dipoles (eg for modelling an LED).

• Plane wave excitor, Gaussian excitor

• Beam excitor: arbitrary beam source, supporting user-defined beam direction, focal point, polarisation and intensity profile.

• Time envelopes: continuous wave, sinusoidal pulse, sinusoidal rise or user-defined function

Sensors

• Time-domain results and frequency-domain results through Fourier analysis

• Q-Factor calculator - calculate Q-factor of resonance in typically 1/4 the time compared to using a Fourier Transform

• Farfield Calculator

• Net flux, forward flux and backward flux sensors versus time, frequency or wavelength.

• Measurement of mode power in waveguide modes using built-in mode solver or imported mode profiles (e.g. from FIMMWAVE)

• Export spatial profiles for flux, field components or intensity in any XZ, YZ or XY plane at a chosen wavelength

• Box sensors:

  • measure total flux in/out of a box; useful for e.g. photo detector efficiency simulation

  • measure the mode volume of your optical cavity.

Additional features

• Storing / Restoring results from an FDTD calculation

• Batch manager - submit multiple jobs to the engine at same time.

• Run time monitoring of evolving fields: watch the fields propagate in real time!

• Video capture - generate a video of your FDTD simulation using any codec installed in your PC.  

Optional modules for the FDTD Engine

• Cluster version available for both Windows and Linux at reasonable cost

• Active FDTD