# Apertures¶

Apertures in the IPKISS AWG Designer are components that feed a field from a waveguide into the Free Propagation Region, or vice versa. In physics nomenclature, the aperture is the opening itself, but for the purpose of the IPKISS AWG Designer we use it to designate the whole component, typically a form of taper or a multi-mode structure, and its opening into the Slab waveguide that is the Free Propagation Region.

Apertures have

• a Layout
• a FieldModel which defines the near field at the opening into the Slab
• A CircuitModel which defines the scatter parameters from the input waveguide to the fields at the opening.

To get started building your own aperture PCell we recommend looking at the ‘Building an Aperture’ tutorial.

The FieldModel and CircuitModel can be defined manually (see for example OpenWireWgAperture.FieldModelFromFunction), or can be calculated automatically with CAMFR (see for example OpenWireWgAperture.FieldModelFromCamfr). The latter method will run an eigenmode propagation simulation throughout the tapered region.

The IPKISS AWG Designer contains a number of predefined aperture types which you can start from. Depending on the foundry / technology used, the apertures can be further finetuned (in terms of layout and model) and are part of the Process Design Kit (PDK).

 OpenTransitionAperture Aperture consisting of a transition between two waveguide templates OpenWireWgAperture An aperture tapering from a wire waveguide to the Slab opening.
 MultiAperture An aperture consisting of multiple single apertures. MultiApertureShallowMerged Multi aperture consisting of individual shallow-etched rib apertures which are merged together. MultiApertureMerged Multi aperture specifically consisting of individual apertures merged together.