Optical Waveguides: Numerical Modeling
 

Eigenmode Expansion Method (EMEM): Software

CAMFR (CAvity Modelling FRamework)

CAMFR is being distributed under a dual license scheme. All the code is released under the GPL, but a closed proprietary license scheme can be also provided. CAMFR was developed by Ghent University (Belgium) photonics group.

CAMFR is a full-vectorial Maxwell solver based on the eigenmode expansion method. Although it can handle general electromagnetic problems, its main focus is on applications in the field of photonics.

Capabilities:

  • CAMFR treats the field as a sum of local eigenmodes in each z-invariant layer and does not rely on spatial discretisation and finite differences to solve Maxwell's equations (like other methods, e.g. FDTD, do).
  • Since there is no spatial discretisation, CAMFR can be orders of magnitude faster than FDTD for a large class of structures.
  • Incorporates advanced boundary conditions (like e.g. PML), which can drastically improve simulation accurary and speed.
  • CAMFR is an ongoing active research project.
  • Two-dimensional Cartesian structures and three-dimensional cylindrical symmetric structures
  • CAMFR can be used to calculate:
    • The scattering matrix of a structure
    • The field inside a structure, for any given excitation
    • Band diagrams of an infinite periodic structure
    • Threshold material gain and resonance wavelength of laser modes
    • The response to a current source in an arbitrary cavity
    • Structures terminated by a semi-infinite repetition of another structure
  • Defining structures is quite straightforward, either layer-by-layer, or using geometric primitive shapes. There are also integrated plotting routines for rapid simulation feedback.
  • CAMFR is conceived as a C++ framework, with all the algorithms implemented in terms of abstract waveguides and scatterers. This makes it extremely easy to extend CAMFR to new geometries.
  • The end user does not deal with this C++ code directly, but rather through bindings to the Python scripting language.

Applications:

  • Wavelength-scale microstructures (like photonic crystal devices)
  • Lasers (like vertical-cavity surface-emitting lasers)
  • Light-emitting diodes (like resonant-cavity LEDs)

Related Publications:

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FIMMPROP

Commercial software software sold by Photon Design.

FIMMPROP is a tool for simulating two- and three-dimensional propagation phenomena in waveguides based on the eigenmode expansion (EME) method.

Capabilities:

  • Fully vectorial
  • The EME method enables the fields to be calculated using fast semi analytical methods.
  • The speed and nature of the calculations allow the propagation to be treated in a fully bi-directional manner, taking into account all the reflections at intermediate joints.
  • This makes FIMMPROP capable of modeling structures which are insolvable by other methods such as BPM.
  • Modeling devices with strong internal reflections, such as waveguides terminated by a tilted facet.
  • Use of semi-analytical modal methods by FIMMPROP permits calculations to achieve high accuracy even for more complicated structures.
  • Z-variant structures are modeled by joining two or more straight sections together.
  • Once the local modes of the structure are found then propagation along the length of the section is near-instantaneous.
  • Calculations permit both transmission and reflection coefficients of the modes at each joint to be determined for use in the fully bi-directional propagation algorithm.
  • Structures with Z-varying cross-sections such as tapers and Y-junctions are computed using sophisticated extensions to the EME method.
  • The algorithm builds a scattering matrix description of the device and all its elements, which means that once the matrices are generated, the response to many different input profiles can be found without further computation, e.g. one might want response to both TE and TM excitation.
  • If the structure is altered, the routine needs only recalculate the elements that have changed.

Applications:

  • MMI couplers
  • Mode converters
  • Codirectional couplers (e.g. polarization converters)
  • Bends
  • Periodic structures
  • Tilted joins
  • Facets and free space regions, e.g. for waveguide-gap-fiber simulations.
  • Propagation in free space is treated with a special efficient algorithm based on plane wave expansion techniques

Related Publications:

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OlympIOs Bidirectional Eigenmode Propagation (BEP) Module

Commercial software sold by OlympIOs.

The bidirectional eigenmode propagation method (BEP) is one of the modules OlympIOs currently offers for simulating the propagation of light through planar waveguide structures.

Capabilities:

  • OlympIOs is the only commercially available platform that integrates the BEP method with the well known Beam Propagation Method (BPM) in a single user interface. The end-user can simulate (parts of) the device using the fastest and most appropriate method.
  • Analysis of waveguide structures that include large waveguide sections invariant in the propagation direction
  • Includes guided and radiation modes
  • Simulates reflections
  • Perfectly Matched Layer (PML) boundary conditions
  • Can handle high index contrast
  • Can handle very wide propagation angles
  • Avoids redundant calculations in vary runs
  • Generic simulation features:
    • Extensive parameterization capabilities
    • Vary runs
    • Material library

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