# Surface Field Monitor

A Surface Field Monitor records electromagnetic fields in the frequency domain on perfect electric conductor (PEC) and non-penetrable lossy-metal surfaces inside a three-dimensional monitor region. Selecting E records the electric field normal to each surface, while selecting H records the magnetic field tangential to each surface.

This object corresponds to tidy3d.SurfaceFieldMonitor (opens new window).

The monitor region must have a nonzero size along all three axes.

WARNING

Surface monitors are currently a beta feature. Verify surface monitor results carefully.

# Name

name: Unique name for the monitor.

  • Required field

# Geometry

Specification of the three-dimensional monitor region.

# Center+Size

Object definition through a center position and size.

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

  • Type: floating-point number
  • Unit: m, mm (default unit), um

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

  • Type: floating-point number
  • Unit: m, mm (default unit), um
  • Constraint: greater than 0 along every axis
  • Required field

# Bounds

Object definition through minimum and maximum coordinate bounds.

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

  • Type: floating-point number
  • Unit: m, mm (default unit), um
  • Required field

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

  • Type: floating-point number
  • Unit: m, mm (default unit), um
  • Required field

NOTE

Surface monitors require a 3D volume. The minimum and maximum bounds must differ along every axis; 1D and 2D regions are not supported.

# Settings

# Fields

fields: Surface field groups stored by the monitor.

  • Options:
    • E: Electric field normal to each supported metal surface.
    • H: Magnetic field tangential to each supported metal surface.
  • Default: E and H
  • Constraint: select at least one field group

NOTE

Selecting only E records the normal electric field, but derived surface current density Js is unavailable. Selecting only H records the tangential magnetic field and supports derived Js. Poynting-vector data requires both E and H. Selecting neither E nor H is invalid.

# Frequency

freqs: Frequencies at which the surface fields are recorded.

Frequency points can be entered by range or as a custom list in the frequency settings panel.

See Frequency Settings.

# Advanced

colocate: Colocate the recorded fields on each supported metal surface. This setting is labeled Colocate fields in the GUI.

  • Type: boolean
  • Default: True
  • Constraint: fixed to True for surface monitors

use_colocated_integration: Use colocated fields for flux, dot-product, and overlap integrations. This setting is labeled Use colocated integration in the GUI.

  • Type: boolean
  • Default: True
  • Constraint: fixed to True for surface monitors

interval_space: Number of grid-step intervals between recorded points in the x, y, and z-directions. This setting is labeled Subsample spatial grid in the GUI.

  • Type: three positive integers
  • Default: (1, 1, 1)
  • Constraint: fixed to (1, 1, 1); spatial downsampling is not currently supported

apodization: Optional apodization window applied to frequency-domain surface field data.

See Apodization Specification.

NOTE

Colocate fields, Use colocated integration, and Subsample spatial grid describe fixed surface-monitor behavior and are informational rather than freely editable.

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