Summary of Monitors in Ansys Lumerical FDTD — Lesson 8

Monitors record data from simulations. Available monitors in FDTD are:


  • Measures refractive index and surface conductivity over space.
  • Used to check mesh order and meshed structure cross-section.


  • Measures E, H fields over time by default.
  • Returns E, H, the spectrum of E and H.
  • Can record and return P if specified.


  • Generates an mp4 movie file in the current working directory showing the specified field component vs. time over the monitor area.

Frequency-domain monitors (power and profile)

  • Shows frequency-domain E, H data by default.
  • Returns E, H and T.
  • T gives net transmission and is only available for linear or 2D monitors in 2D simulations or 2D monitors in 3D simulations.
  • Can return P if specified.
  • Power uses the nearest mesh cell interpolation, whereas profile uses the specified position.

Mode expansion

  • Performs overlap calculations between calculated modes and recorded fields from a frequency domain monitor to get the power traveling in selected modes of a waveguide or fiber.
  • Can be used to extract S-parameters of a device, although using Port objects is simpler.

The global monitor properties settings window can be opened from the Monitors menu in the top toolbar.


  • Added using the Ports button in the top toolbar.
  • Acts as a mode source as well as a power monitor and mode expansion monitor.
  • Returns the same results as mode source, power monitor, and mode expansion monitor in addition to S result which gives the S-parameter.
  • The port group, which is a child of the FDTD simulation region, contains all port objects and sets the active port and mode to use as the source in the simulation.
  • Ports can be used in conjunction with the S-parameter sweep tool to extract the full S-parameters of a device and export the S-parameters to INTERCONNECT for circuit simulations.