FIMMPROP

FIMMPROP offers both great control and high flexibility to design 3D structures, thanks to its extensive element library.

A large variety of z-varying sections and joints are provided to allow efficient design and fast and accurate simulations, thanks to the optimisation of the algorithms associated with each type of element.

A device is built by linking together predefined sections and joints.

Simulate tapered waveguides, bends and couplers of all kinds

A section may be one of the following:

A straight waveguide-section.

A bent waveguide-section, in which the waveguide is bent in an arc horizontally or vertically with a specified curvature along a given angle.

A tapered waveguide-section, defined between a start and an end waveguide cross-section. To modulate the variation of the structure along the taper, FIMMPROP offers a choice of linear, exponential or user defined taper functions - e.g. you can define a structure where lateral dimensions vary linearly, layer thicknesses vary exponentially and a layer refractive index varies according to your own tabulated function. The definition is sufficiently general so that you can model more complex structures such as Y junctions using concatenated "taper" sections.

A variation of the taper section allows to design a lens described by a waveguide cross-section. The lens is defined through its diameter and radius of curvature.

It is also possible to fully define a complex 3D device from a simple 1D epitaxial layer structure thanks to the Ridge Section, as can be seen below with this Mach Zehnder interferometer.

Introduce tilt, offsets and free space propagation between waveguides

Two different kinds of joints are available:

- the simple joint which models juxtaposed facets. Its implementation is based on overlap integrals, with the possibility of including rotation, tilts and offsets to model virtually any kind of facet configuration.

- the free-space joint which permits propagation through air or any other uniform medium, in addition to the features of the simple joint. It is based on a plane-wave decomposition of the field and provides the user with a simple way to add thin film coatings on the facets.

Periodic sections

FIMMPROP also permits to design periodic sections in an automated way. All you need to do is define the period and tell FIMMPROP how many of them you want. Thanks to the scattering matrix approach, you will only need to calculate the modes and scattering matrix for the period once. The rest of the calculation is instantaneous, regardless of how many periods you are using. This also applies to structures in which a given section is being repeated.

Flexible Layout for 2D structures

The FIMMPROP Layout permits to design very complex 1D+Z structures with a great flexibility. The resolution of 1D+Z structures in FIMMPROP is fully analytical, and hence extremely fast and accurate.