# ModeABCBoundary

Specifies a one-way wave equation absorbing boundary condition (ABC) for absorbing a specific waveguide mode.

This boundary condition is designed to efficiently absorb guided modes propagating in waveguides, making it ideal for waveguide simulations where you want to minimize reflections at the simulation boundaries.

# Mode Selection

You can select between defining the component from scratch (Custom) or getting mode specifications from existing sources or monitors.

Options:

  • Custom: define all the component parameters
  • Source: select mode specifications from an existing mode source
  • Monitor: select mode specifications from an existing mode monitor

See: ModeSpec

# Geometry

plane: Cross-sectional plane in which the absorbed mode will be computed.

  • Required field
  • Must be a planar geometry (one dimension must have zero size)

# Center + size

Object definition through a center position and size.

center: Center of the object in x, y, and z-directions.

Type: floating-point number

  • Unit: m, μm (default), or nm
  • Default: (0, 0, 0)

size: Size of the object in x, y, and z-directions.

Use Infinity to define a geometry extending to infinity in both directions along an axis.

Type: floating-point number

  • Unit: m, μm (default), or nm
  • Constraint: greater than or equal to 0
  • Required field

# Bounds

Object definition through minimum and maximum coordinate bounds.

min: Values of the x, y, and z coordinates defining the object lower corner.

Type: floating-point number

  • Unit: m, μm (default), or nm
  • Required field

max: Values of the x, y, and z coordinates defining the object upper corner.

Type: floating-point number

  • Unit: m, μm (default), or nm
  • Required field

# Mode Index

mode_index: Index into the collection of modes returned by the mode solver. The absorbing boundary conditions are configured to absorb the specified mode.

Type: integer

  • Unit: unitless
  • Constraint: greater than or equal to 0
  • Default: 0

Note: If the mode index is larger than mode_spec.num_modes, the solver will automatically set num_modes to mode_index + 1.

# Frequency Specification

freq_spec: Specifies the frequency at which the field is absorbed.

Options:

  • None (default): Uses the central frequency of the source
  • Frequency value: A specific frequency in Hz
  • BroadbandModeABCSpec: Absorbs the field over a specified frequency range

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